Researcher Profile and Settings

Master

Affiliation (Master)

• Research Faculty of Agriculture　Research Innovation and Cooperation　Cooperative Promotion

Affiliation (Master)

• Research Faculty of Agriculture　Research Innovation and Cooperation　Cooperative Promotion

researchmap

Profile and Settings

Affiliation

• Hokkaido University, Graduate School of Agriculture Research Faculty of Agriculture Task Force for Innovation in Life,Resources and Environment Sciences, Associate Professor

Profile and Settings

• Name (Japanese)

  Ezawa

• Name (Kana)

  Tatsuhiro

• Name

  B-7735-2012, 200901048062903806

通称等の別名

Tatsu Ezawa

Alternate Names

http://www.agr.hokudai.ac.jp/botagr/rhizo/RhizoCont/index.html
http://www.agr.hokudai.ac.jp/botagr/rhizo/RhizoCont/Rhizo_en.html

Affiliation

• Hokkaido University, Graduate School of Agriculture Research Faculty of Agriculture Task Force for Innovation in Life,Resources and Environment Sciences, Associate Professor

Achievement

Research Interests

• 植物栄養・土壌学   Plant-microbe symbiosis   Plant physiology   Soil microbiology   

Research Areas

• Life sciences / Plant nutrition, soil science

Research Experience

• 2004 - Today Hokkaido University Research Faculty of Agriculture Associate Prof.
• 2000 - 2004 Nagoya University Graduate School of Bioagricultral Science Assistant Prof.
• 1998 - 2000 Adelaide University, Australia Department of Soil and Water Research fellow
• 1994 - 1998 Nagoya University Faculty of Agriculture Assistant Prof.
• 1989 - 1992 Kyowa Hakko Kogyo Co., Ltd. Tsukuba Research Laboratories Researcher

Education

• 1992 - 1994  Chiba University  Graduate School of Natural Science
•        - 1994  Chiba University  Graduate School, Division of National Science and Technology
• 1987 - 1989  Hokkaido University  Graduate School of Agriculture
•        - 1989  Hokkaido University  Graduate School, Division of Agriculture

Committee Memberships

• 2022/10 - Today   Japan Mycorrhizal Research Society   President
• 2020/05 - Today   Frontiers in Microbiology   Associate Editor
• 2021/04 -2023/03   Soil Science and Plant Nutrition   Associate Editor-In-Chief

Awards

• 2022/05 Japanese Sciety for Soil Science and Plant Nutrition Sciety Award
   Molecular bases and envrionmental responses of nutrient delivery in arbuscular mycorrhizal symbiosis 

  受賞者: Tatsuhiro Ezawa
• 2002 日本土壌肥料学会 奨励賞
   パイオニア植物の侵入・定着における共生微生物の役割 

  受賞者: 江沢辰広
• 2001 東海学術奨励会 研究奨励賞
   強酸性土壌の植生回復技術に関する基礎的研究：パイオニア植物の侵入・定着における共生微生物の役割 

  受賞者: 江沢辰広

Published Papers

• Role of life-history strategies of arbuscular mycorrhizal fungi in partner selection by a juvenile C4 grass under low-light conditions

  Anjar Cahyaningtyas, Tatsuhiro Ezawa

  2024/08/02
• Disturbance tolerance of arbuscular mycorrhizal fungi: characterization of life-history strategies along a disturbance gradient in a coastal dune ecosystem

  Anjar Cahyaningtyas, Tatsuhiro Ezawa

  Plant and Soil 495 (1-2) 535 - 549 0032-079X 2023/10/24
• Structurally distinct mitoviruses: are they an ancestral lineage of the Mitoviridae exclusive to arbuscular mycorrhizal fungi (Glomeromycotina)?

  Tatsuhiro Ezawa, Alessandro Silvestri, Hayato Maruyama, Keitaro Tawaraya, Mei Suzuki, Yu Duan, Massimo Turina, Luisa Lanfranco

  mBio 2023/05/10 

  Mitoviruses in the family Mitoviridae are the mitochondria-replicating “naked RNA viruses” with genomes encoding only the replicase RNA-dependent RNA polymerase (RdRp) and prevalent across fungi, plants, and invertebrates. Arbuscular mycorrhizal fungi in the subphylum Glomeromycotina are obligate plant symbionts that deliver water and nutrients to the host. We discovered distinct mitoviruses in glomeromycotinian fungi, namely “large duamitovirus,” encoding unusually large RdRp with a unique N-terminal motif that is endogenized in some host genomes. More than 400 viral sequences similar to the large duamitoviruses are present in metatranscriptome databases. They are globally distributed in soil ecosystems, consistent with the cosmopolitan distribution of glomeromycotinian fungi, and formed the most basal clade of the Mitoviridae in phylogenetic analysis. Given that glomeromycotinian fungi are the only confirmed hosts of these viruses, we propose the hypothesis that large duamitoviruses are the most ancestral lineage of the Mitoviridae that have been maintained exclusively in glomeromycotinian fungi.
• Plant Foraging Strategies Driven by Distinct Genetic Modules: Cross-Ecosystem Transcriptomics Approach

  Yusaku Sugimura, Ai Kawahara, Hayato Maruyama, Tatsuhiro Ezawa

  Frontiers in Plant Science 13 1664-462X 2022/07/04 [Refereed]
   

  Plants have evolved diverse strategies for foraging, e.g., mycorrhizae, modification of root system architecture, and secretion of phosphatase. Despite extensive molecular/physiological studies on individual strategies under laboratory/greenhouse conditions, there is little information about how plants orchestrate these strategies in the field. We hypothesized that individual strategies are independently driven by corresponding genetic modules in response to deficiency/unbalance in nutrients. Roots colonized by mycorrhizal fungi, leaves, and root-zone soils were collected from 251 maize plants grown across the United States Corn Belt and Japan, which provided a large gradient of soil characteristics/agricultural practice and thus gene expression for foraging. RNA was extracted from the roots, sequenced, and subjected to gene coexpression network analysis. Nineteen genetic modules were defined and functionally characterized, from which three genetic modules, mycorrhiza formation, phosphate starvation response (PSR), and root development, were selected as those directly involved in foraging. The mycorrhizal module consists of genes responsible for mycorrhiza formation and was upregulated by both phosphorus and nitrogen deficiencies. The PSR module that consists of genes encoding phosphate transporter, secreted acid phosphatase, and enzymes involved in internal-phosphate recycling was regulated independent of the mycorrhizal module and strongly upregulated by phosphorus deficiency relative to nitrogen. The root development module that consists of regulatory genes for root development and cellulose biogenesis was upregulated by phosphorus and nitrogen enrichment. The expression of this module was negatively correlated with that of the mycorrhizal module, suggesting that root development is intrinsically an opposite strategy of mycorrhizae. Our approach provides new insights into understanding plant foraging strategies in complex environments at the molecular level.
• Establishing a quality management framework for commercial inoculants containing arbuscular mycorrhizal fungi

  Matthias J. Salomon, Stephanie J. Watts-Williams, Michael J. McLaughlin, Heike Bücking, Brajesh K. Singh, Imke Hutter, Carolin Schneider, Francis M. Martin, Miroslav Vosatka, Liangdong Guo, Tatsuhiro Ezawa, Masanori Saito, Stéphane Declerck, Yong-Guan Zhu, Timothy Bowles, Lynette K. Abbott, F. Andrew Smith, Timothy R. Cavagnaro, Marcel G.A. van der Heijden

  iScience 25 (7) 104636 - 104636 2589-0042 2022/07 [Refereed][Not invited]
  
• Polyphosphate polymerizing and depolymerizing activity of VTC4 protein in an arbuscular mycorrhizal fungus

  Cuc Thi Nguyen, Tatsuhiro Ezawa, Katsuharu Saito

  Soil Science and Plant Nutrition 68 (2) 256 - 267 0038-0768 2022/03/04
• Asymbiotic mass production of the arbuscular mycorrhizal fungus Rhizophagus clarus

  Sachiko Tanaka, Kayo Hashimoto, Yuuki Kobayashi, Koji Yano, Taro Maeda, Hiromu Kameoka, Tatsuhiro Ezawa, Katsuharu Saito, Kohki Akiyama, Masayoshi Kawaguchi

  Communications Biology 5 (1) 2022/01/12 

  Abstract Arbuscular mycorrhizal (AM) symbiosis is a mutually beneficial interaction between fungi and land plants and promotes global phosphate cycling in terrestrial ecosystems. AM fungi are recognised as obligate symbionts that require root colonisation to complete a life cycle involving the production of propagules, asexual spores. Recently, it has been shown that Rhizophagus irregularis can produce infection-competent secondary spores asymbiotically by adding a fatty acid, palmitoleic acid. Furthermore, asymbiotic growth can be supported using myristate as a carbon and energy source for their asymbiotic growth to increase fungal biomass. However, the spore production and the ability of these spores to colonise host roots were still limited compared to the co-culture of the fungus with plant roots. Here we show that a combination of two plant hormones, strigolactone and jasmonate, induces the production of a large number of infection-competent spores in asymbiotic cultures of Rhizophagus clarus HR1 in the presence of myristate and organic nitrogen. Inoculation of asymbiotically-generated spores promoted the growth of host plants, as observed for spores produced by symbiotic culture system. Our findings provide a foundation for the elucidation of hormonal control of the fungal life cycle and the development of inoculum production schemes.
• Tracking an Introduced Arbuscular Mycorrhizal Fungus in Allium fistulosum in a Field Condition With or Without Controlling Indigenous Fungi by Soil Fumigation As Well as Evaluation on Plant Phosphorus and Growth

  Takumi Sato, Rieko Niwa, Tatsuhiro Ezawa, Shusei Sato, Hideki Hirakawa, Shigenobu Yoshida, Weiguo Cheng, Keitaro Tawaraya

  JOURNAL OF SOIL SCIENCE AND PLANT NUTRITION 21 (4) 2781 - 2790 0718-9508 2021/12 

  Increased plant phosphorus uptake and growth as a result of inoculation with arbuscular mycorrhizal (AM) fungi is observed less often under field conditions than in pot experiments. Interaction between introduced and indigenous AM fungi is one of the reasons for ineffectiveness of inoculation in the field. We aimed to distinguish the effect of introduced and indigenous AM fungi on phosphorus uptake and growth of Allium fistulosum in a field experiment. Superphosphate was applied in the ratio of 0 or 317 P kg ha(-1) to the plots fumigated with or without dazomet that is a common soil fumigant. Seedlings of A. fistulosum that had been inoculated with or without Rhizophagus spp. strain R-10 were transplanted into the plots. AM fungal colonization, OTU read abundance of indigenous and introduced AM fungi, shoot P concentration, and shoot growth were measured at 31, 60, 90, and 131 days after transplanting (DAT). We could partially separate the effects of introduced AM fungi from indigenous AM fungi by fumigation with dazomet. Though neither inoculation nor P level affected shoot fresh weight and shoot P content in the non-fumigated main plot at 131 DAT, significantly higher shoot fresh weight was obtained by the inoculation with no P fertilizer in the fumigated main plot at this final sampling stage. These results indicate that the colonization of roots by introduced AM fungi is affected by the abundance of indigenous AM fungi and this interaction determines growth response of host plants under field conditions.
• 3-1-17 コムギにおける菌根特異的遺伝子群のゲノム内重複と発現制御機構の保存性（3-1 土壌生物の生態と機能 2021年度北海道大会）

  坂上 桃花, 青山 奈央, 杉原 創, 丸山 隼人, 江沢 辰広

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 67 31 - 31 0288-5840 2021/09/03
• 3-1-19 葉の遺伝子発現による地下微生物機能の診断（3-1 土壌生物の生態と機能 2021年度北海道大会）

  江沢 辰広, 杉村 悠作, 丸山 隼人

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 67 32 - 32 0288-5840 2021/09/03
• Editorial: Pyrophosphates and Polyphosphates in Plants and Microorganisms

  Jos{\'{e } } R. P{\'{e } }rez-Casti{\~{n } }eira, Roberto Docampo, Tatsuhiro Ezawa, Aurelio Serrano

  Frontiers in Plant Science 12 1664-462X 2021/03/26 [Refereed][Invited]
  
• Cross-ecosystem transcriptomics identifies distinct genetic modules for nutrient acquisition in maize

  Yusaku Sugimura, Ai Kawahara, Hayato Maruyama, Tatsuhiro Ezawa

  bioRxiv 2020/09/03 [Not refereed][Not invited]
   

  Plants have evolved diverse strategies for the acquisition of the macro-nutrients phosphorus and nitrogen; e.g., mycorrhizal formation, root development, and secretion of chelators/hydrolases to liberate inorganic phosphate. Despite the extensive studies on the individual strategies, there is little information about how plants regulate these strategies in response to fluctuating environment. We approached this issue via profiling transcriptomes of plants grown in large environmental gradients. Roots, leaves, and root-zone soils of 251 maize plants were collected across the US Corn Belt and Japan. RNA was extracted from the roots and sequenced, and the leaves and soils were analyzed. Nineteen genetic modules were defined by weighted gene coexpression network analysis and functionally characterized according to gene ontology analysis, by which we found three modules that are directly involved in nutrient acquisition: mycorrhizal formation, phosphate-starvation response (PSR), and root development. Correlation analysis with soil and plant factors revealed that both phosphorus and nitrogen deficiencies upregulated the mycorrhizal module, whereas the PSR module was upregulated mainly by deficiency in phosphorus relative to nitrogen. Expression levels of the root development module were negatively correlated with those of the mycorrhizal module, suggesting that nutrient acquisition through the two pathways, mycorrhizas and roots, are opposite strategies that are employed under nutrient-deficient and -enriched conditions, respectively. The identification of the soil and plant factors that drive the modules has implications for sustainable agriculture; activation/optimization of the strategies is feasible via manipulating the factors. Overall, our study opens a new window for understanding plant response to complex environments.
• Conservation and host-specific expression of non-tandemly repeated heterogenous ribosome RNA gene in arbuscular mycorrhizal fungi

  Taro Maeda, Yuuki Kobayashi, Tomomi Nakagawa, Tatsuhiro Ezawa, Katsushi Yamaguchi, Takahiro Bino, Yuki Nishimoto, Shuji Shigenobu, Masayoshi Kawaguchi

  bioRxiv 2020/05/15 [Not refereed][Not invited]
   

  The ribosomal RNA-encoding gene (rDNA) has a characteristic genomic nature: tens to thousands of copies in a genome, tandemly repeated structure, and intragenomic sequence homogeneity. These features contribute to ribosome productivity via physiological and evolutionary processes. We reported previously the exceptional absence of these features in the model arbuscular mycorrhizal (AM) fungusRhizophagus irregularis.Here we examine the phylogenetic distribution of the exceptional rDNA features in the genusRhizophagusvia improving the genome sequence ofR. clarus.Cross-species comparison indicated similarity of their rDNAs not only in the genomic features but also in the distribution of intragenomic polymorphic sites on the paralogs. Ribosomal RNA comprises multiple domains with different functions. The twoRhizophagusspecies commonly exhibited a variation enrichment site, ES27L, which is related to translational fidelity and antibiotic sensitivity. Variation enrichment on ES27L has not been observed in other organisms lacking the three rDNA features such as malaria parasites andCyanidioschyzon merolae.Expression profiling of rDNAs inR. irregularisrevealed that rDNA paralogs are expressed differently in association with host plant species. Our results suggest a broad distribution of the disarranged rDNA across AM fungi and its involvement in the successful association with the broad range of host species.
• 3-1-42 農耕地利用の強度に応答したアーバスキュラー菌根菌群集の収斂と多様性の維持機構（3-1 土壌生物の生態と機能 2020年度岡山大会）

  丹羽 理恵子, 小八重 善裕, 大友 量, 林 正紀, 唐澤 敏彦, 神山 拓也, 丸山 隼人, 江沢 辰広, 佐藤 修正, 平川 英樹, 吉田 重信, 佐藤 孝, 鈴木 貴恵, 佐藤 匠, 俵谷 圭太郎, 福永 亜矢子

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 66 34 - 34 0288-5840 2020
• Application of Virus-Induced Gene Silencing to Arbuscular Mycorrhizal Fungi

  Tatsuhiro Ezawa

  Methods in Molecular Biology 249 - 254 1064-3745 2020 [Refereed][Invited]
  
• Secretion of acid phosphatase from extraradical hyphae of the arbuscular mycorrhizal fungus Rhizophagus clarus is regulated in response to phosphate availability

  Takumi Sato, Shihomi Hachiya, Nozomi Inamura, Tatsuhiro Ezawa, Weiguo Cheng, Keitaro Tawaraya

  Mycorrhiza 29 (6) 599 - 605 0940-6360 2019/11 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi increase phosphate (P) uptake by plants. Organic phosphate comprises 30-80% of total P in most agricultural soils. Some plants can utilize organic phosphate by secreting acid phosphatase (ACP) fromtheir roots, especially under low P conditions. Although secretion of ACP from extraradical hyphae of AM fungi has been reported, the specific factors that affect the secretion of ACP are unknown. The objective of the present study was to investigate whether secretion of ACP from extraradical hyphae is induced by low P conditions. First, specimens of Allium fistulosum were either inoculated with the AM fungus Rhizophagus clarus strain CK001 or remained uninoculated and were grown in soil with 0.5 g P2O5 kg(-1) soil or without P fertilization using two-compartment pots. Soil solution was collected using mullite ceramic tubes 45 days after sowing. The soil solution was analyzed for ACP activity by using p-nitrophenylphosphate. Second, Ri T-DNA transformed roots (i.e., hairy roots) of Linum usitatissimum inoculated with R. clarus were grown on solid minimal media with two P levels applied (3 and 30 mu M P) using two-compartment Petri dishes under in vitro conditions. Hyphal exudates, extraradical hyphae, and hairy roots were collected and analyzed for ACP activity. ACP activity in the soil solution of the hyphal compartment in the A. fistulosum inoculation treatment was higher without P fertilization than with P fertilization. AM colonization also was higher without P fertilization than with P fertilization. In the in vitro two-compartment culture, ACP activity of hyphal exudates and extraradical hyphae were higher under the 3-mu M treatment than under the 30-mu Mtreatment. These findings suggest that the secretion of ACP from the extraradical hyphae of R. clarus into the hyphosphere is promoted under low P conditions.
• Stimulation of asymbiotic sporulation in arbuscular mycorrhizal fungi by fatty acids

  Hiromu Kameoka, Ippo Tsutsui, Katsuharu Saito, Yusuke Kikuchi, Yoshihiro Handa, Tatsuhiro Ezawa, Hideo Hayashi, Masayoshi Kawaguchi, Kohki Akiyama

  Nature Microbiology 4 (10) 1654 - 1660 2019/10/01 [Refereed][Not invited]
   

  © 2019, The Author(s), under exclusive licence to Springer Nature Limited. Arbuscular mycorrhizal (AM) fungi are obligate symbionts that depend on living host plants to complete their life cycle1,2. This feature, which leads to their unculturability in the absence of plants, strongly hinders basic research and agricultural application of AM fungi. However, at least one AM fungus can grow and develop fertile spores independently of a host plant in co-culture with the bacterium Paenibacillus validus3. The bacteria-derived substances are thought to act as stimulants or nutrients for fungal sporulation, but these molecules have not been identified. Here, we show that (S)-12-methyltetradecanoic acid4,5, a methyl branched-chain fatty acid isolated from bacterial cultures, stimulates the branching of hyphae germinated from mother spores and the formation of secondary spores in axenic culture of the AM fungus Rhizophagus irregularis. Extensive testing of fatty acids revealed that palmitoleic acid induces more secondary spores than the bacterial fatty acid in R. irregularis. These induced spores have the ability to infect host plant roots and to generate daughter spores. Our work shows that, in addition to a major source of organic carbon6–9, fatty acids act as stimulants to induce infection-competent secondary spores in the asymbiotic stage and could provide the key to developing the axenic production of AM inoculum.
• Globular structures in roots accumulate phosphorus to extremely high concentrations following phosphorus addition

  Ryan, Megan H., Kaur, Parwinder, Nazeri, Nazanin K., Clode, Peta L., Keeble-Gagnère, Gabriel, Doolette, Ashlea L., Smernik, Ronald J., Van Aken, Olivier, Nicol, Dion, Maruyama, Hayato, Ezawa, Tatsuhiro, Lambers, Hans, Millar, A. Harvey, Appels, Rudi

  Plant, Cell & Environment 42 (6) 1987 - 2002 1365-3040 2019/06 [Refereed][Not invited]
  
• Impact of Introduction of Arbuscular Mycorrhizal Fungi on the Root Microbial Community in Agricultural Fields.

  Turgut Yigit Akyol, Rieko Niwa, Hideki Hirakawa, Hayato Maruyama, Takumi Sato, Takae Suzuki, Ayako Fukunaga, Takashi Sato, Shigenobu Yoshida, Keitaro Tawaraya, Masanori Saito, Tatsuhiro Ezawa, Shusei Sato

  Microbes and Environments 34 (1) 23 - 32 2019/03/30 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi are important members of the root microbiome and may be used as biofertilizers for sustainable agriculture. To elucidate the impact of AM fungal inoculation on indigenous root microbial communities, we used high-throughput sequencing and an analytical pipeline providing fixed operational taxonomic units (OTUs) as an output to investigate the bacterial and fungal communities of roots treated with a commercial AM fungal inoculum in six agricultural fields. AM fungal inoculation significantly influenced the root microbial community structure in all fields. Inoculation changed the abundance of indigenous AM fungi and other fungal members in a field-dependent manner. Inoculation consistently enriched several bacterial OTUs by changing the abundance of indigenous bacteria and introducing new bacteria. Some inoculum-associated bacteria closely interacted with the introduced AM fungi, some of which belonged to the genera Burkholderia, Cellulomonas, Microbacterium, Sphingomonas, and Streptomyces and may be candidate mycorrhizospheric bacteria that contribute to the establishment and/or function of the introduced AM fungi. Inoculated AM fungi also co-occurred with several indigenous bacteria with putative beneficial traits, suggesting that inoculated AM fungi may recruit specific taxa to confer better plant performance. The bacterial families Methylobacteriaceae, Acetobacteraceae, Armatimonadaceae, and Alicyclobacillaceae were consistently reduced by the inoculation, possibly due to changes in the host plant status caused by the inoculum. To the best of our knowledge, this is the first large-scale study to investigate interactions between AM fungal inoculation and indigenous root microbial communities in agricultural fields.
• Nestedness in Arbuscular Mycorrhizal Fungal Communities in a Volcanic Ecosystem: Selection of Disturbance-tolerant Fungi along an Elevation Gradient

  Tatsuhiro Ezawa

  Microbes and Environments 34 (3) 327 - 333 1342-6311 2019 [Refereed][Not invited]
  
• How do arbuscular mycorrhizal fungi handle phosphate? New insight into fine‐tuning of phosphate metabolism

  Tatsuhiro Ezawa, Katsuharu Saito

  New Phytologist 220 (4) 1116 - 1121 2018/12 [Refereed][Invited]
  
• 3-1-12 有機質肥料の施用が植物リン利用効率と菌根菌感染ポテンシャルに与える影響（ミニシンポジウム，3-1 土壌生物の生態と機能，2018年度神奈川大会）

  杉山 知穂, 杉村 悠作, 長竹 新, 安田 花穂, 八巻 憲和, 平 克郎, 河合 正人, 江沢 辰広, 波多野 隆介

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 64 29 - 29 0288-5840 2018/08/29
• The genome of Rhizophagus clarus HR1 reveals a common genetic basis for auxotrophy among arbuscular mycorrhizal fungi

  Yuuki Kobayashi, Taro Maeda, Katsushi Yamaguchi, Hiromu Kameoka, Sachiko Tanaka, Tatsuhiro Ezawa, Shuji Shigenobu, Masayoshi Kawaguchi

  BMC Genomics 19 (1) 465  1471-2164 2018/06/18 [Refereed][Not invited]
   

  Background: Mycorrhizal symbiosis is one of the most fundamental types of mutualistic plant-microbe interaction. Among the many classes of mycorrhizae, the arbuscular mycorrhizae have the most general symbiotic style and the longest history. However, the genomes of arbuscular mycorrhizal (AM) fungi are not well characterized due to difficulties in cultivation and genetic analysis. In this study, we sequenced the genome of the AM fungus Rhizophagus clarus HR1, compared the sequence with the genome sequence of the model species R. irregularis, and checked for missing genes that encode enzymes in metabolic pathways related to their obligate biotrophy. Results: In the genome of R. clarus, we confirmed the absence of cytosolic fatty acid synthase (FAS), whereas all mitochondrial FAS components were present. A KEGG pathway map identified the absence of genes encoding enzymes for several other metabolic pathways in the two AM fungi, including thiamine biosynthesis and the conversion of vitamin B6 derivatives. We also found that a large proportion of the genes encoding glucose-producing polysaccharide hydrolases, that are present even in ectomycorrhizal fungi, also appear to be absent in AM fungi. Conclusions: In this study, we found several new genes that are absent from the genomes of AM fungi in addition to the genes previously identified as missing. Missing genes for enzymes in primary metabolic pathways imply that AM fungi may have a higher dependency on host plants than other biotrophic fungi. These missing metabolic pathways provide a genetic basis to explore the physiological characteristics and auxotrophy of AM fungi.
• Dissection of niche competition between introduced and indigenous arbuscular mycorrhizal fungi with respect to soybean yield responses.

  Rieko Niwa, Takuya Koyama, Takumi Sato, Katsuki Adachi, Keitaro Tawaraya, Shusei Sato, Hideki Hirakawa, Shigenobu Yoshida, Tatsuhiro Ezawa

  Scientific Reports 8 (1) 7419 - 7419 2018/05/09 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi associate with most land plants and deliver phosphorus to the host. Identification of biotic/abiotic factors that determine crop responses to AM fungal inoculation is an essential step for successful application of the fungi in sustainable agriculture. We conducted three field trials on soybean with a commercial inoculum and developed a new molecular tool to dissect interactions between the inoculum and indigenous fungi on the MiSeq sequencing platform. Regression analysis indicated that sequence read abundance of the inoculum fungus was the most significant factor that determined soybean yield responses to the inoculation, suggesting that dominance of the inoculum fungus is a necessary condition for positive yield responses. Agricultural practices (fallow/cropping in the previous year) greatly affected the colonization levels (i.e. read abundances) of the inoculum fungus via altering the propagule density of indigenous AM fungi. Analysis of niche competition revealed that the inoculum fungus competed mainly with the indigenous fungi that are commonly distributed in the trial sites, probably because their life-history strategy is the same as that of the inoculum fungus. In conclusion, we provide a new framework for evaluating the significance of environmental factors towards successful application of AM fungi in agriculture.
• Inoculum effect of arbuscular mycorrhizal fungi on soybeans grown in long-term bare-fallowed field with low phosphate availability

  Hayashi Masaki, Niwa Rieko, Urashima Yasufumi, Suga Yuko, Sato Shusei, Hirakawa Hideki, Yoshida Shigenobu, Ezawa Tatsuhiro, Karasawa Toshihiko

  Soil Science and Plant Nutrition Informa UK Limited 64 (3) 306 - 311 0038-0768 2018/05/04 [Refereed][Not invited]
  
• 3-2-1 機械学習アルゴリズムを用いたネギにおけるアーバスキュラー菌根菌接種効果の発現予測（3-2 土壌生物の応用と制御，2018年度神奈川大会）

  丹羽 理恵子, 福永 亜矢子, 江沢 辰広, 佐藤 修正, 平川 英樹, 吉田 重信, 佐藤 孝, 鈴木 貴恵, 齋藤 雅典, 佐藤 匠, 俵谷 圭太郎

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 64 41 - 41 0288-5840 2018
• Stringent Expression Control of Pathogenic R-body Production in Legume Symbiont Azorhizobium caulinodans

  Jun-ichi Matsuoka, Fumiko Ishizuna, Keigo Kurumisawa, Kengo Morohashi, Tetsuhiro Ogawa, Makoto Hidaka, Katsuharu Saito, Tatsuhiro Ezawa, Toshihiro Aono

  mBio 8 (4) 2150-7511 2017/07 [Refereed][Not invited]
   

  R bodies are insoluble large polymers consisting of small proteins encoded by reb genes and are coiled into cylindrical structures in bacterial cells. They were first discovered in Caedibacter species, which are obligate endosymbionts of paramecia. Caedibacter confers a killer trait on the host paramecia. R-body-producing symbionts are released from their host paramecia and kill symbiont-free paramecia after ingestion. The roles of R bodies have not been explained in bacteria other than Caedibacter. Azorhizobium caulinodans ORS571, a microsymbiont of the legume Sesbania rostrata, carries a reb operon containing four reb genes that are regulated by the repressor PraR. Herein, deletion of the praR gene resulted in R-body formation and death of host plant cells. The rebR gene in the reb operon encodes an activator. Three PraR binding sites and a RebR binding site are present in the promoter region of the reb operon. Expression analyses using strains with mutations within the PraR binding site and/or the RebR binding site revealed that PraR and RebR directly control the expression of the reb operon and that PraR dominantly represses reb expression. Furthermore, we found that the reb operon is highly expressed at low temperatures and that 2-oxoglutarate induces the expression of the reb operon by inhibiting PraR binding to the reb promoter. We conclude that R bodies are toxic not only in paramecium symbiosis but also in relationships between other bacteria and eukaryotic cells and that R-body formation is controlled by environmental factors. IMPORTANCE Caedibacter species, which are obligate endosymbiotic bacteria of paramecia, produce R bodies, and R-body-producing endosymbionts that are released from their hosts are pathogenic to symbiont-free paramecia. Besides Caedibacter species, R bodies have also been observed in a few free-living bacteria, but the significance of R-body production in these bacteria is still unknown. Recent advances in genome sequencing technologies revealed that many Gram-negative bacteria possess reb genes encoding R-body components, and interestingly, many of them are animal and plant pathogens. Azorhizobium caulinodans, a microsymbiont of the tropical legume Sesbania rostrata, also possesses reb genes. In this study, we demonstrate that A. caulinodans has ability to kill the host plant cells by producing R bodies, suggesting that pathogenicity conferred by an R body might be universal in bacteria possessing reb genes. Furthermore, we provide the first insight into the molecular mechanism underlying the expression of R-body production in response to environmental factors, such as temperature and 2-oxoglutarate.
• 3-2-2 管理・環境要因に基づいたネギにおけるアーバスキュラー菌根菌接種効果発現の予測モデル構築（3-2 土壌生物の応用と制御，2017年度仙台大会）

  丹羽 理恵子, 福永 亜矢子, 江沢 辰広, 佐藤 修正, 平川 英樹, 吉田 重信, 佐藤 孝, 鈴木 貴恵, 齋藤 雅典, 佐藤 匠, 俵谷 圭太郎

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 63 42 - 42 0288-5840 2017
• A putative TetR-type transcription factor AZC_3265 from the legume symbiont Azorhizobium caulinodans represses the production of R-bodies that are toxic to eukaryotic cells

  Jun-ichi Matsuoka, Fumiko Ishizuna, Keigo Kurumisawa, Kengo Morohashi, Tetsuhiro Ogawa, Makoto Hidaka, Katsuharu Saito, Tatsuhiro Ezawa, Toshihiro Aono

  SOIL SCIENCE AND PLANT NUTRITION 63 (5) 452 - 459 0038-0768 2017 [Refereed][Not invited]
   

  Azorhizobium caulinodans ORS571 is a microsymbiont of the legume Sesbania rostrata, which forms nitrogen-fixing nodules on stems and roots. This bacterium harbors a reb operon, which is associated with R-body production. R-bodies are large proteinaceous ribbons and were first observed in Caedibacter species, which are obligate bacterial endosymbionts in paramecia. R-body-producing Caedibacter species released from their host paramecia are toxic to the symbiont-free paramecia. R-body-producing cells of A. caulinodans mutants are also toxic to the plant host cells. To maintain harmonic symbiosis with S. rostrata, A. caulinodans has to repress the expression of the reb operon. To date, it has been revealed that the PraR transcription factor and Lon protease repress reb operon expression, in direct and indirect manners, respectively. In this study, we carried out transposon-based mutagenesis screening, and found that the AZC_3265 (locus tag on the genome) gene encoding a putative TetR-type transcription factor was involved in the repression of reb operon expression. The AZC_3265 gene deletion mutant showed high levels of reb operon expression and R-body formation, and this strain formed stem nodules defective in nitrogen-fixing activity. Systematic evolution of ligands by exponential enrichment (SELEX) experiment revealed that AZC_3265 protein could bind to the consensus palindromic sequence TTGC-N6-GCAA. However, this consensus sequence was not found in the reb operon promoter region. Additionally, an electrophoretic mobility shift assay (EMSA) also revealed that AZC_3265 could not bind to the reb operon promoter region. These results suggested that AZC_3265 repressed the expression of the reb operon in an indirect manner. In conclusion, the present data demonstrated that multiple regulators participate in the regulation of expression of the reb operon. The presence of multiple mechanisms for regulating the expression of the reb operon suggested that its expression was controlled in response to multiple biological and environmental factors.
• How special do you have to be to live in acidic soil?

  Kawahara, A, An, G-H, Miyakawa, S, Sonoda, J, Ezawa, T

  Environmental Science Journal for Teens 2017 [Not refereed][Invited]
  
• Phosphorus metabolism and transport in arbuscular mycorrhizal symbiosis

  Katsuharu Saito, Tatsuhiro Ezawa

  Molecular Mycorrhizal Symbiosis 197 - 216 2016/10/28 [Not refereed][Invited]
   

  Phosphorus (P) is an essential element for plant growth and development. Plants take up P as orthophosphate (Pi) from soil solution, but Pi concentration in the solution is generally low, particularly in the rhizosphere in which Pi is seriously depleted by plant Pi uptake. Formation of symbiotic associations with AM fungi is a widespread plant strategy for enhancing Pi uptake from soil beyond the P-depletion zone. Mycorrhizal plants have two pathways for Pi acquisition - one via the root epidermis, and the other via AM fungal hyphae. AM fungi construct hyphal networks both in root cortex and soil, and form highly branched hyphal termini-arbuscules-on intercellular hyphae or on intracellular coils in the cortex. This chapter reviews the latest knowledge of the mechanism underlying the Pi delivery system in arbuscular mycorrhizal (AM) symbiosis at the physiological, cytological, and molecular levels.
• Nestedness in Arbuscular Mycorrhizal Fungal Communities along Soil pH Gradients in Early Primary Succession: Acid-Tolerant Fungi Are pH Generalists

  Ai Kawahara, Gi-Hong An, Sachie Miyakawa, Jun Sonoda, Tatsuhiro Ezawa

  PLoS ONE 11 (10) e0165035  1932-6203 2016/10 [Refereed][Not invited]
   

  Soil acidity is a major constraint on plant productivity. Arbuscular mycorrhizal (AM) fungi support plant colonization in acidic soil, but soil acidity also constrains fungal growth and diversity. Fungi in extreme environments generally evolve towards specialists, suggesting that AM fungi in acidic soil are acidic-soil specialists. In our previous surveys, however, some AM fungi detected in strongly acidic soils could also be detected in a soil with moderate pH, which raised a hypothesis that the fungi in acidic soils are pH generalists. To test the hypothesis, we conducted a pH-manipulation experiment and also analyzed AM fungal distribution along a pH gradient in the field using a synthesized dataset of the previous and recent surveys. Rhizosphere soils of the generalist plant Miscanthus sinensis were collected both from a neutral soil and an acidic soil, and M. sinensis seedlings were grown at three different pH. For the analysis of field communities, rhizosphere soils of M. sinensis were collected from six field sites across Japan, which covered a soil pH range of 3.0-7.4, and subjected to soil trap culture. AM fungal community compositions were determined based on LSU rDNA sequences. In the pH-manipulation experiment the acidification of medium had a significant impact on the compositions of the community from the neutral soil, but the neutralization of the medium had no effect on those of the community from the acidic soil. Furthermore, the communities in lower-pH soils were subsets of (nested in) those in higher-pH soils. In the field communities a significant nestedness pattern was observed along the pH gradient. These observations suggest that the fungi in strongly acidic soils are pH generalists that occur not only in acidic soil but also in wide ranges of soil pH. Nestedness in AM fungal community along pH gradients may have important implications for plant community resilience and early primary succession after disturbance in acidic soils.
• Aquaporin-mediated long-distance polyphosphate translocation directed towards the host in arbuscular mycorrhizal symbiosis: application of virus-induced gene silencing

  Yusuke Kikuchi, Nowaki Hijikata, Ryo Ohtomo, Yoshihiro Handa, Masayoshi Kawaguchi, Katsuharu Saito, Chikara Masuta, Tatsuhiro Ezawa

  New Phytologist 211 (4) 1202 - 1208 0028-646X 2016/09 [Refereed][Not invited]
   

  Arbuscular mycorrhizal fungi translocate polyphosphate through hyphae over a long distance to deliver to the host. More than three decades ago, suppression of host transpiration was found to decelerate phosphate delivery of the fungal symbiont, leading us to hypothesize that transpiration provides a primary driving force for polyphosphate translocation, probably via creating hyphal water flow in which fungal aquaporin(s) may be involved. The impact of transpiration suppression on polyphosphate translocation through hyphae of Rhizophagus clarus was evaluated. An aquaporin gene expressed in intraradical mycelia was characterized and knocked down by virus-induced gene silencing to investigate the involvement of the gene in polyphosphate translocation.Rhizophagus clarus aquaporin 3 (RcAQP3) that was most highly expressed in intraradical mycelia encodes an aquaglyceroporin responsible for water transport across the plasma membrane. Knockdown of RcAQP3 as well as the suppression of host transpiration decelerated polyphosphate translocation in proportion to the levels of knockdown and suppression, respectively. These results provide the first insight into the mechanism underlying long-distance polyphosphate translocation in mycorrhizal associations at the molecular level, in which host transpiration and the fungal aquaporin play key roles. A hypothetical model of the translocation is proposed for further elucidation of the mechanism.
• 耐酸性菌根菌 (Rhizophagus clarus RF1) 資材を用いた酸性土壌法面の緑化工

  Tatsuhiro Ezawa

  日本緑化工学会誌 Journal of the Japanese Society of Revegetation Technology 42 (1) 156‐159  0916-7439 2016/08/31 [Not refereed][Not invited]
  
• 植物の耐酸性を向上させる耐酸性菌根菌

  江澤, 辰広, 河原, 愛, 中西, 夏輝, 山梨, 太郎, 堀江, 直樹

  日本緑化工学会誌 Journal of the Japanese Society of Revegetation Technology 42 (1) 153‐155  0916-7439 2016/08/31 [Not refereed][Not invited]
  
• P3-1-10 アーバスキュラー菌根菌における耐酸性形質の分子基盤へのアプローチ（ポスター，3-1 土壌生物の生態と機能，2016年度佐賀大会）

  中西 夏輝, 江沢 辰広

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 62 34 - 34 2016
• 3-2-11 酸性土壌に分布するアーバスキュラー菌根菌の生態と緑化資材としての適性（3-2 土壌生物の応用と制御，2016年度佐賀大会）

  江沢 辰広, 河原 愛, 安 起弘, 宮川 祥江, 牧 孝憲, 中西 夏輝, 山梨 太郎, 堀江 直樹

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 62 41 - 41 2016
• P7-2-1 菌根菌資材接種がダイズの生育・収量に及ぼす影響（ポスター，7-2 土壌改良資材，2016年度佐賀大会）

  大友 量, 小八重 善裕, 森本 晶, 江沢 辰広, 岡 紀邦

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 62 139 - 139 2016
• 3-1-19 アーバスキュラー菌根菌大陸間隔離株における同一ウイルスの存在が示唆する宿主ーウイルス共生の起源（3-1 土壌生物の生態と機能，2016年度佐賀大会）

  鈴木 芽以, 前田 太郎, 小林 裕樹, 川口 正代司, 俵谷 圭太郎, 増田 税, 江澤 辰広

  日本土壌肥料学会講演要旨集 一般社団法人 日本土壌肥料学会 62 30 - 30 2016
• Inorganic polyphosphates in mycorrhiza

  Tatsuhiro Ezawa, Chiharu Tani, Nowaki Hijikata, Yusuke Kikuchi

  Inorganic Polyphosphates in Eukaryotic Cells 49 - 60 2016/01/01 [Not refereed][Invited]
   

  Mycorrhizas are the mutualistic associations between fungi and plant roots. Mycorrhizal fungi construct hyphal networks both in the soil (extraradical mycelia) and root cortex (intraradical mycelia), take up mineral nutrients, in particular phosphate, from the soil, and deliver to the host. In turn, the host supplies carbon source to the fungi. Phosphate is an essential nutrient for plants, but its diffusion in the soil is slow. Extraradical mycelia can explore a larger volume of soil than roots for phosphate acquisition, and the fungi deliver phosphate to the host more rapidly than the diffusion of Pi in the soil. Similar to "polyphosphate overplus" in yeast and bacteria, mycorrhizal fungi are capable of accumulating a massive amount of polyphosphate in the vacuoles quite rapidly, which provides large buffering capacity and storage of phosphate that is to be delivered to the host. Phosphate is taken up via H+ /phosphate and Na+ /phosphate symporters, incorporated to γ-phosphate of ATP, polymerized by the vacuolar transporter chaperone complex in the tonoplast using ATP as a phosphoryl donor, and released into the vacuole, during which Na+, K+, Mg2+, and Ca2+ are taken up via cation transporters synchronously and equivalently with polyphosphate accumulation to maintain charge neutrality of the cell. The genes encoding these transporters and ATPases are upregulated in response to increased external phosphate concentration, implying that polyphosphate accumulation is achieved by orchestrated regulation of the expression of various genes. Although the molecular mechanism of polyphosphate accumulation has recently been studied extensively, driving force for polyphosphate translocation toward the host of mycorrhizal fungi has not been well understood.
• 第二，第三次技術革新が開くアーバスキュラー菌根共生研究 —栄養共生機構・生態・ビジネス展望—

  江沢辰広

  日本土壌肥料学会誌 87 64 - 69 2016 [Not refereed][Invited]
  
• Up-regulation of genes involved in N-acetylglucosamine uptake and metabolism suggests a recycling mode of chitin in intraradical mycelium of arbuscular mycorrhizal fungi

  Yoshihiro Kobae, Miki Kawachi, Katsuharu Saito, Yusuke Kikuchi, Tatsuhiro Ezawa, Masayoshi Maeshima, Shingo Hata, Toru Fujiwara

  MYCORRHIZA 25 (5) 411 - 417 0940-6360 2015/07 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi colonize roots and form two kinds of mycelium, intraradical mycelium (IRM) and extraradical mycelium (ERM). Arbuscules are characteristic IRM structures that highly branch within host cells in order to mediate resource exchange between the symbionts. They are ephemeral structures and at the end of their life span, arbuscular branches collapse from the tip, fungal cytoplasm withdraws, and the whole arbuscule shrinks into fungal clumps. The exoskeleton of an arbuscule contains structured chitin, which is a polymer of N-acetylglucosamine (GlcNAc), whereas a collapsed arbuscule does not. The molecular mechanisms underlying the turnover of chitin in AM fungi remain unknown. Here, a GlcNAc transporter, RiNGT, was identified from the AM fungus Rhizophagus irregularis. Yeast mutants defective in endogenous GlcNAc uptake and expressing RiNGT took up C-14-GlcNAc, and the optimum uptake was at acidic pH values (pH 4.0-4.5). The transcript levels of RiNGT in IRM in mycorrhizal Lotus japonicus roots were over 1000 times higher than those in ERM. GlcNAc-6-phosphate deacetylase (DAC1) and glucosamine-6-phosphate isomerase (NAG1) genes, which are related to the GlcNAc catabolism pathway, were also induced in IRM. Altogether, data suggest the existence of an enhanced recycling mode of GlcNAc in IRM of AM fungi.
• Difference in Striga-susceptibility is reflected in strigolactone secretion profile, but not in compatibility and host preference in arbuscular mycorrhizal symbiosis in two maize cultivars

  Kaori Yoneyama, Ryota Arakawa, Keiko Ishimoto, Hyun Il Kim, Takaya Kisugi, Xiaonan Xie, Takahito Nomura, Fred Kanampiu, Takao Yokota, Tatsuhiro Ezawa, Koichi Yoneyama

  NEW PHYTOLOGIST 206 (3) 983 - 989 0028-646X 2015/05 [Refereed][Not invited]
   

  Strigolactones released from plant roots trigger both seed germination of parasitic weeds such as Striga spp. and hyphal branching of the symbionts arbuscular mycorrhizal (AM) fungi. Generally, strigolactone composition in exudates is quantitatively and qualitatively different among plants, which may be involved in susceptibility and host specificity in the parasite-plant interactions. We hypothesized that difference in strigolactone composition would have a significant impact on compatibility and host specificity/preference in AM symbiosis. Strigolactones in root exudates of Striga-susceptible (Pioneer 3253) and -resistant (KST 94) maize (Zea mays) cultivars were characterized by LC-MS/MS combined with germination assay using Striga hermonthica seeds. Levels of colonization and community compositions of AM fungi in the two cultivars were investigated in field and glasshouse experiments. 5-Deoxystrigol was exuded exclusively by the susceptible cultivar, while the resistant cultivar mainly exuded sorgomol. Despite the distinctive difference in strigolactone composition, the levels of AM colonization and the community compositions were not different between the cultivars. The present study demonstrated that the difference in strigolactone composition has no appreciable impact on AM symbiosis, at least in the two maize cultivars, and further suggests that the traits involved in Striga-resistance are not necessarily accompanied by reduction in compatibility to AM fungi.
• Release of acid phosphatase from extraradical hyphae of arbuscular mycorrhizal fungus Rhizophagus clarus

  Takumi Sato, Tatsuhiro Ezawa, Weiguo Cheng, Keitaro Tawaraya

  SOIL SCIENCE AND PLANT NUTRITION 61 (2) 269 - 274 0038-0768 2015/03 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi enhance plant uptake of available phosphorus (P) from soil through their extraradical hyphae. The mechanism underlying this P uptake enhanced by AM fungi is the increase in the surface area for absorption of available P. Little is known about utilization of unavailable P by AM fungi. We investigated whether extraradical hyphae of AM fungi release acid phosphatase (ACP). Sterilized Andosol was packed in pots that were separated into the mycorrhizal and hyphal compartments with a nylon net of 30-mu m pore size. Seeds of Allium fistulosum L. were inoculated or uninoculated with the AM fungus Rhizophagus clarus (Nicolson & Schenck) Walker & Schu ss ler. Mullite ceramic tubes were buried in the soil of each compartment, and soil solution was collected. A. fistulosum L. and Linum usitatissimum L. inoculated with R. clarus were grown in sand culture and in vitro monoxenic culture, respectively. Uninoculated A. fistulosum L was grown in hydroponic culture to collect root exudate. The soil solution, hyphal extracts, root extract and root exudates were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Shoot P concentration, shoot P content and shoot dry weight were higher in the inoculated treatment than in the uninoculated treatment. Activity staining of the gel revealed that ACP activity at 187kDa was observed in the soil solution in the inoculation treatment, and in the hyphal extract collected from sand culture and in vitro monoxenic culture, but neither in the root exudate of non-mycorrhizal plant grown in the hydroponic culture nor in the root extracts irrespective of mycorrhizal status. Those results provide strong evidence that the corresponding activity in the soil solutions in soil culture is of R. clarus CK001 origin. These findings suggest that the fungus releases ACP from extraradical hyphae into the hyphosphere.
• Shoot-derived signals other than auxin are involved in systemic regulation of strigolactone production in roots

  Kaori Yoneyama, Takaya Kisugi, Xiaonan Xie, Ryota Arakawa, Tatsuhiro Ezawa, Takahito Nomura, Koichi Yoneyama

  PLANTA 241 (3) 687 - 698 0032-0935 2015/03 [Refereed][Not invited]
   

  Nitrogen and phosphorus fertilization in one side of split-root sorghum plants systemically reduced root contents of strigolactones in both sides of the split roots. Shoot-derived signals other than auxin appeared to be involved in this process. Strigolactones (SLs) are a novel class of plant hormones regulating both shoot and root architectures and suggested to be functioning downstream of auxin. The levels of SLs in plant tissues and root exudates are regulated by nutrients, especially phosphorus (P) and nitrogen (N); however, the underlying mechanism remains elusive. We examined the effects of N and P fertilization on root contents of two SLs, sorgomol and 5-deoxystrigol, in sorghum plants pre-incubated under N and P free conditions using a split-root system. N and P fertilization to one side of the split-root plants systemically reduced root contents of SLs in both sides of the split roots. The shoot N and P levels increased when one side of the split-root plants was fertilized, while N and P levels in the non-fertilized split roots were unaffected. N fertilization decreased shoot and root IAA (indole-3-acetic acid) levels, while P fertilization did not affect them. IAA applied to the shoot apices increased root contents of 5-deoxystrigol but not that of sorgomol only when the plants were grown under P free conditions. Shoot (leaf) removal dramatically decreased the root contents of SLs but did not affect root IAA levels, and IAA applied to the stumps of leaves could not restore root contents of SLs. Consequently, shoot-derived signals other than auxin are suggested to be involved in the regulation of SL production in roots.
• Polyphosphate accumulation is driven by transcriptome alterations that lead to near-synchronous and near-equivalent uptake of inorganic cations in an arbuscular mycorrhizal fungus

  Yusuke Kikuchi, Nowaki Hijikata, Kaede Yokoyama, Ryo Ohtomo, Yoshihiro Handa, Masayoshi Kawaguchi, Katsuharu Saito, Tatsuhiro Ezawa

  New Phytologist 204 (3) 638 - 649 1469-8137 2014/11/01 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi accumulate a massive amount of phosphate as polyphosphate to deliver to the host, but the underlying physiological and molecular mechanisms have yet to be elucidated. In the present study, the dynamics of cationic components during polyphosphate accumulation were investigated in conjunction with transcriptome analysis. Rhizophagus sp. HR1 was grown with Lotus japonicus under phosphorus-deficient conditions, and extraradical mycelia were harvested after phosphate application at prescribed intervals. Levels of polyphosphate, inorganic cations and amino acids were measured, and RNA-Seq was performed on the Illumina platform. Phosphate application triggered not only polyphosphate accumulation but also near-synchronous and near-equivalent uptake of Na+, K+, Ca2+ and Mg2+, whereas no distinct changes in the levels of amino acids were observed. During polyphosphate accumulation, the genes responsible for mineral uptake, phosphate and nitrogen metabolism and the maintenance of cellular homeostasis were up-regulated. The results suggest that inorganic cations play a major role in neutralizing the negative charge of polyphosphate, and these processes are achieved by the orchestrated regulation of gene expression. Our findings provide, for the first time, a global picture of the cellular response to increased phosphate availability, which is the initial process of nutrient delivery in the associations.
• A unique mitovirus from Glomeromycota, the phylum of arbuscular mycorrhizal fungi

  Ryoko Kitahara, Yoji Ikeda, Hanako Shimura, Chikara Masuta, Tatsuhiro Ezawa

  ARCHIVES OF VIROLOGY 159 (8) 2157 - 2160 0304-8608 2014/08 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi that belong to the phylum Glomeromycota associate with most land plants and supply mineral nutrients to the host plants. One of the four viral segments found by deep-sequencing of dsRNA in the AM fungus Rhizophagus clarus strain RF1 showed similarity to mitoviruses and is characterized in this report. The genome segment is 2,895 nucleotides in length, and the largest ORF was predicted by applying either the mold mitochondrial or the universal genetic code. The ORF encodes a polypeptide of 820 amino acids with a molecular mass of 91.2 kDa and conserves the domain of the mitovirus RdRp superfamily. Accordingly, the dsRNA was designated as R. clarus mitovirus 1 strain RF1 (RcMV1-RF1). Mitoviruses are localized exclusively in mitochondria and thus generally employ the mold mitochondrial genetic code. The distinct codon usage of RcMV1-RF1, however, suggests that the virus is potentially able to replicate not only in mitochondria but also in the cytoplasm. RcMV1-RF1 RdRp showed the highest similarity to the putative RdRp of a mitovirus-like ssRNA found in another AM fungus, followed by RdRp of a mitovirus in an ascomycotan ectomycorrhizal fungus. The three mitoviruses found in the three mycorrhizal fungi formed a deeply branching clade that is distinct from the two major clades in the genus Mitovirus.
• Detection and Characterization of Mycoviruses in Arbuscular Mycorrhizal Fungi by Deep-Sequencing

  Ezawa Tatsuhiro, Ikeda Yoji, Shimura Hanako, Masuta Chikara

  Methods in Molecular Biology springer 1236 171 - 180 1064-3745 2014 [Refereed][Invited]
   

  Fungal viruses (mycoviruses) often have a significant impact not only on phenotypic expression of the host fungus but also on higher order biological interactions, e.g., conferring plant stress tolerance via an endophytic host fungus. Arbuscular mycorrhizal (AM) fungi in the phylum Glomeromycota associate with most land plants and supply mineral nutrients to the host plants. So far, little information about mycoviruses has been obtained in the fungi due to their obligate biotrophic nature. Here we provide a technical breakthrough, "two-step strategy" in combination with deep-sequencing, for virological study in AM fungi; dsRNA is first extracted and sequenced using material obtained from highly productive open pot culture, and then the presence of viruses is verified using pure material produced in the in vitro monoxenic culture. This approach enabled us to demonstrate the presence of several viruses for the first time from a glomeromycotan fungus.
• Characterization of arbuscular mycorrhizal fungal communities with respect to zonal vegetation in a coastal dune ecosystem

  Ai Kawahara, Tatsuhiro Ezawa

  OECOLOGIA 173 (2) 533 - 543 0029-8549 2013/10 [Refereed][Not invited]
   

  Coastal dune vegetation distributes zonally along the environmental gradients of, e.g., soil disturbance. In the preset study, arbuscular mycorrhizal fungal communities in a coastal dune ecosystem were characterized with respect to tolerance to soil disturbance. Two grass species, Elymus mollis and Miscanthus sinensis, are distributed zonally in the seaward and landward slopes, respectively, in the primary dunes in Ishikari, Japan. The seaward slope is severely disturbed by wind, while the landward slope is stabilized by the thick root system of M. sinensis. The roots and rhizosphere soils of the two grasses were collected from the slopes. The soils were sieved to destruct the fungal hyphal networks, and soil trap culture was conducted to assess tolerance of the communities to disturbance, with parallel analysis of the field communities using a molecular ecological tool. In the landward communities, large shifts in the composition and increases in diversity were observed in the trap culture compared with the field, but in the seaward communities, the impact of trap culture was minimal. The landward field community was significantly nested within the landward trap culture community, implying that most members in the field community did not disappear in the trap culture. No nestedness was observed in the seaward communities. These observations suggest that disturbance-tolerant fungi have been preferentially selected in the seaward slope due to severe disturbance in the habitat. Whereas a limited number of fungi, which are not necessarily disturbance-sensitive, dominate in the stable landward slope, but high-potential diversity has been maintained in the habitat.
• Ninety-year-, but not single, application of phosphorus fertilizer has a major impact on arbuscular mycorrhizal fungal communities

  Ying Cheng, Keiko Ishimoto, Yuko Kuriyama, Mitsuru Osaki, Tatsuhiro Ezawa

  PLANT AND SOIL 365 (1-2) 397 - 407 0032-079X 2013/04 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi play a significant role in P nutrition of crops in agriculture, but P accumulation in the soil, e.g., application of P-fertilizer, generally reduces AM fungal colonization. The impact of long-term application of chemical fertilizer on AM fungal communities was investigated with respect to the time scale. Soils were collected from four plots with different fertilizer management in the long-term experimental field established in 1914. Lotus japonicus was grown in the soils in a greenhouse, while Glycine max was grown in the plots in the field. DNA was extracted from their roots, and the diversity and community compositions were analyzed based on occurrence of the AM fungal phylotypes defined by sequence similarity in the LSU rDNA. The 90-year-application of N and K in the absence of P increased AM fungal diversity and resulted in formation of a distinctive fungal community compared with those in the other treatments. This effect was not cancelled by single application of P. Whereas the impact of balanced application of N, P, and K was ambiguous. These observations suggest that the presence/absence of P-fertilizer has a major impact on AM fungal communities, but the action may appear only on a long time scale.
• A Novel Virus-Like Double-Stranded RNA in an Obligate Biotroph Arbuscular Mycorrhizal Fungus: A Hidden Player in Mycorrhizal Symbiosis

  Yoji Ikeda, Hanako Shimura, Ryoko Kitahara, Chikara Masuta, Tatsuhiro Ezawa

  MOLECULAR PLANT-MICROBE INTERACTIONS 25 (7) 1005 - 1012 0894-0282 2012/07 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi form mutualistic associations with most land plants and enhance phosphorus uptake of the host plants. Fungal viruses (mycoviruses) that possess a double-stranded RNA (dsRNA) genome often affect plant fungal interactions via altering phenotypic expression of their host fungi. The present study demonstrates, for the first time, the presence of dsRNAs, which are highly likely to be mycoviruses, in AM fungi. dsRNA was extracted from mycelia of G/omus sp. strain RF1, purified, and subjected to electrophoresis. The fungus was found to harbor various dsRNA segments that differed in size. Among them, a 4.5-kbp segment was termed Glomus sp. strain RF1 virus-like medium dsRNA (GRF1V-M) and characterized in detail. The GRF1V-M genome segment was 4,557 nucleotides in length and encoded RNA-dependent RNA polymerase and a structural protein. GRF1V-M was phylogenetically distinct and could not be assigned to known genera of mycovirus. The GRF1V-M-free culture line of G/omus sp. strain RF1, which was raised by single-spore isolation, produced twofold greater number of spores and promoted plant growth more efficiently than the GRF1V-M-positive lines. These observations suggest that mycoviruses in AM fungi, at least some of them, have evolved under unique selection pressures and are a biologically active component in the symbiosis.
• 強酸性土壌に棲息するアーバスキュラー菌根菌: パイオニア植生を支える 「化石的」 絶対共生菌

  江沢辰広, 河原愛

  生物科学 63 (4) 238 - 246 0045-2033 2012 [Refereed][Invited]
  
• Complete Sructure of Nuclear rDNA of the Obligate Plant Parasite Plasmodiophora brassicae: Intraspecific Polymorphisms in the Exon and Group I Intron of the Large Subunit rDNA

  Rieko Niwa, Ai Kawahara, Hiroharu Murakami, Shuhei Tanaka, Tatsuhiro Ezawa

  PROTIST 162 (3) 423 - 434 1434-4610 2011/07 [Refereed][Not invited]
   

  Plasmodiophora brassicae is a soil-borne obligate intracellular parasite in the phylum Cercozoa of the Rhizaria that causes clubroot disease of crucifer crops. To control the disease, understanding the distribution and infection routes of the pathogen is essential, and thus development of reliable molecular markers to discriminate geographic populations is required. In this study, the nuclear ribosomal RNA gene (rDNA) repeat unit of P. brassicae was determined, with particular emphasis on the structure of large subunit (LSU) rDNA, in which polymorphic regions were expected to be present. The complete rDNA complex was 9513 bp long, which included the small subunit, 5.8S and LSU rDNAs as well as the internal transcribed spacer and intergenic spacer regions. Among eight field populations collected from throughout Honshu Island, Japan, a 1.1 kbp region of the LSU rDNA, including the divergent 8 domain, exhibited intraspecific polymorphisms that reflected geographic isolation of the populations. Two new group I introns were found in this region in six out of the eight populations, and the sequences also reflected their geographic isolation. The polymorphic region found in this study may have potential for the development of molecular markers for discrimination of field populations/isolates of this organism. (C) 2011 Elsevier GmbH. All rights reserved.
• How does arbuscular mycorrhizal colonization vary with host plant genotype? An example based on maize (Zea mays) germplasms

  G. -H. An, S. Kobayashi, H. Enoki, K. Sonobe, M. Muraki, T. Karasawa, T. Ezawa

  PLANT AND SOIL 327 (1-2) 441 - 453 0032-079X 2010/02 [Refereed][Not invited]
   

  Colonization of plant roots by arbuscular mycorrhizal (AM) fungi is a primary factor determining mycorrhizal associations. This study aimed to investigate the variation in AM colonization among maize genotypes and in response to plant breeding programs. Three types of maize (Zea mays) germplasms composed of 141 inbred lines, 38 hybrids, and 76 landraces were grown in replicated field experiments in Sapporo, Japan, for two cropping years to evaluate the percentage of root length colonized by indigenous AM fungi. The percent colonization varied greatly and continuously among maize genotypes. Inbred lines that originated (released) in particular locations (e.g., Tokachi, Japan) and years (e.g., 1960s) showed significantly larger values than other lines. Inter-location differences were also observed for landraces. The direction of the year-of-release effect on colonization depended on the origin. No significant differences were observed between leaf-blight-disease-resistant near-isogenic inbred lines and their parents. Modern hybrids showed significantly greater values than inbred lines and older landraces. Evaluating numerous, diverse genotypes demonstrated that AM colonization of maize plants varies with germplasm type, origin (country and location), and year of release, and that modern plant breeding programs do not necessarily lead to the suppression of colonization.
• Slope vegetation method using mycrorhizal fungi to appearance of effect by acid soil

  TANAKA Jun, HORIE Naoki, EZAWA TATSUHIRO, BAN Sukehide

  The Japanese Association of The Revegetaion Technology 日本緑化工学会 36 (1) 119 - 122 0916-7439 2010 [Refereed][Not invited]
   

  強酸性土壌(pH 2.7～4.7)に生育する植物から分離した耐酸性菌根菌を使用した強酸性法面緑化工法の開発を目指し，実験を行った。pH 3.3～4.0の強酸性土壌の上に，耐酸性菌根菌を入れたポットのメドハギの生育は，入れないものよりも良好であった。しかし，pH 1.8ではすべて枯死し，pH 2.5でも生育は不良となることから，適用できるpHには限界があることが示唆された。また，pH 2.5を下回る強酸性土壌に適用するため，強アルカリの中和資材と併用した場合でも，耐酸性VA菌根菌は，植物の酸性抵抗力を高める効果があることがわかった。以上のことから，耐酸性菌根菌は強酸性土壌の対策資材として有効であると考えられる。
• Polyphosphate has a central role in the rapid and massive accumulation of phosphorus in extraradical mycelium of an arbuscular mycorrhizal fungus

  Nowaki Hijikata, Masatake Murase, Chiharu Tani, Ryo Ohtomo, Mitsuru Osaki, Tatsuhiro Ezawa

  NEW PHYTOLOGIST 186 (2) 285 - 289 1469-8137 2010 [Refereed][Not invited]
  
• ATP-Dependent but Proton Gradient-Independent Polyphosphate-Synthesizing Activity in Extraradical Hyphae of an Arbuscular Mycorrhizal Fungus

  Chiharu Tani, Ryo Ohtomo, Mitsuru Osaki, Yukari Kuga, Tatsuhiro Ezawa

  APPLIED AND ENVIRONMENTAL MICROBIOLOGY 75 (22) 7044 - 7050 0099-2240 2009/11 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi benefit their host plants by supplying phosphate obtained from the soil. Polyphosphate is thought to act as the key intermediate in this process, but little is currently understood about how polyphosphate is synthesized or translocated within arbuscular mycorrhizas. Glomus sp. strain HR1 was grown with marigold in a mesh bag compartment system, and extraradical hyphae were harvested and fractionated by density gradient centrifugation. Using this approach, three distinct layers were obtained: layers 1 and 2 were composed of amorphous and membranous materials, together with mitochondria, lipid bodies, and electron-opaque bodies, and layer 3 was composed mainly of partially broken hyphae and fragmented cell walls. The polyphosphate kinase/luciferase system, a highly sensitive polyphosphate detection method, enabled the detection of polyphosphate-synthesizing activity in layer 2 in the presence of ATP. This activity was inhibited by vanadate but not by bafilomycin A(1) or a protonophore, suggesting that ATP may not energize the reaction through H+-ATPase but may act as a direct substrate in the reaction. This report represents the first demonstration that AM fungi possess polyphosphate-synthesizing activity that is localized in the organelle fraction and not in the cytosol or at the plasma membrane.
• Element interconnections in Lotus japonicus: A systematic study of the effects of element additions on different natural variants

  Zheng Chen, Toshihiro Watanabe, Takuro Shinano, Tatsuhiro Ezawa, Jun Wasaki, Kazuhiko Kimura, Mitsuru Osaki, Yong-Guan Zhu

  SOIL SCIENCE AND PLANT NUTRITION 55 (1) 91 - 101 0038-0768 2009/02 [Refereed][Not invited]
   

  Lotus japonicus was used to study the distribution and interconnections of 15 elements in plant tissues, including essential and non-essential elements: boron (B), sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), strontium (Sr), molybdenum (Mo), cadmium (Cd) and cesium (Cs). Large amounts of B and Ca accumulated in plant leaves, while Fe, Na, Ni, As and Cd tended to mainly occur in the roots, and Mo was the only element to accumulate in the stems. The elemental compositions within plants were severely disturbed by treatment with toxic elements. Competition between element pairs in the same group (e.g. K and Cs; Ca and Sr) was not found. Iron, Cu and Zn accumulation were induced by Cd and Ni addition. When natural variants grew in a nutrition solution with subtoxic levels of As, Cd, Cs, Ni, Mo and Sr, intriguing relationships between the elements (such as Fe, As and K; Mg and Ni; Mn and Ca) were revealed using principal-component analysis. This study on the plant ionome offers detailed information of element interactions and indicates that chemically different elements might be closely linked in uptake or translocation systems.
• Plant symbiotic microorganisms in acid sulfate soil: significance in the growth of pioneer plants

  Takanori Maki, Miya Nomachi, Shigekata Yoshida, Tatsuhiro Ezawa

  PLANT AND SOIL 310 (1-2) 55 - 65 0032-079X 2008/09 [Refereed][Not invited]
   

  Acid sulfate soil is generated by chemical and microbial oxidization of sulfide-rich minerals/sediments. Although revegetation of the soil is difficult due to low-pH and poor nutrient availability, pioneer plants may adapt to such an extreme environment via associating with mycorrhizal fungi and/or N-fixing bacteria for acquisition of mineral nutrients. In this study, an abandoned quarry in which acid sulfate soil was found was chosen to investigate the influence of soil acidity on the levels of colonization by the microsymbionts, the identities of the microsymbionts that associated with pioneer plants and the dependency of pioneer plants on the microsymbionts. The levels of arbuscular mycorrhizal (AM) colonization in pioneer grass, forbs and legume shrubs grown in the field were assessed, and no significant decline in the levels with an increase in soil acidity was observed. Most of the legume shrubs formed root nodules. Several AM fungi and bradyrhizobia were cultured from the rhizosphere soils of pioneer plants grown in the quarry and identified based on the sequences of the small subunit ribosomal RNA genes. Pot experiments revealed that the microsymbionts isolated from the field significantly promoted the growths of pioneer grasses and legume shrubs in acid sulfate soil at pH 3.4. These results suggest that plant-microbial symbiotic associations play significant roles in the growth of pioneer plants in acid sulfate soil.
• Community structure of arbuscular mycorrhizal fungi associated with pioneer grass species Miscanthus sinensis in acid sulfate soils: Habitat segregation along pH gradients

  Gi-Hong An, Sachie Miyakawa, Ai Kawahara, Mitsuru Osaki, Tatsuhiro Ezawa

  SOIL SCIENCE AND PLANT NUTRITION 54 (4) 517 - 528 0038-0768 2008/08 [Refereed][Not invited]
   

  Acid sulfate soil has an extremely low pH and revegetation of the soil is difficult because of the high concentration of toxic elements, such as aluminum, and poor nutrient availability. Community compositions of arbuscular mycorrhizal (AM) fungi that associate with Miscanthus sinensis, a pioneer grass species that occurs in acid sulfate soil, were investigated to clarify the environmental factors that regulate the community structure. The rhizosphere soils of M. sinensis growing in acid sulfate soils were collected from three sites distributed in subarctic, temperate and subtropical zones. Rhizosphere soils of plants growing in a sandy soil site in a subarctic zone were also collected. Miscanthus sinensis seedlings were grown on these soils in a greenhouse for 2 months and a large subunit ribosomal RNA gene of the fungi was amplified from DNA extracted from the roots. Based on the nucleotide sequences of the gene, 20 phylotypes across six genera were detected from the four sites. The similarity indices of AM fungal communities among the sites did not correlate with geographical distance. Ordination analysis (principal component analysis) on the communities suggested that the first principal component reflected edaphic factors, particularly soil pH. Plotting of soil pH data at which respective phylotypes occurred and subsequent statistical analysis revealed that the ranges of preferential pH were significantly different among the phylotypes. The distribution of AM fungal phylotypes along pH gradients was further recognized by plotting the first principal component scores of the phylotypes against their preferential pH. The phylotypes that showed higher scores along the second principal component were detected from three or more sites and occurred over a wide range of pH values. These observations suggest that the preference and range of substrate pH to which the fungi can adapt are different among the phylotypes and soil pH might be a likely driving force for structuring AM fungal communities in acid sulfate soils.
• Polyphosphate kinase is essential for swarming motility, tolerance to environmental stresses, and virulence in Pseudomonas syringae pv. tabaci 6605

  Md. Mijan Hossain, Chiharu Tani, Tomoko Suzuki, Fumiko Taguchi, Tatsuhiro Ezawa, Yuki Ichinose

  PHYSIOLOGICAL AND MOLECULAR PLANT PATHOLOGY 72 (4-6) 122 - 127 0885-5765 2008/07 [Refereed][Not invited]
   

  Polyphosphate kinase (PPK), encoded by the ppk gene, is a principal enzyme responsible for synthesis of inorganic polyphosphate (poly P) from ATP in many Gram-negative bacteria. In order to elucidate the functions of poly P in Pseudomonas syringae pv. tabaci 6605, an in-frame deletion mutant of the ppk gene (Delta ppk) was constructed. The Delta ppk mutant did not accumulate poly P, whereas the wild-type strain accumulated a large quantity. The mutant had reduced swarming motility, even though it retains swimming motility like the parental strain. The mutant exhibited increased sensitivity to prolonged incubation and environmental stresses, such as heat shock and oxidative stress and reduced exopolysaccharide (EPS) production compared to the wild-type. Northern blot analysis revealed that expression of the rpoS gene, encoding the stationary phase sigma factor RpoS, was reduced in Delta ppk in the logarithmic phase, indicating that rpoS is regulated by the ppk gene. The poly P deficient mutant had significantly reduced ability to cause disease in its host tobacco plant and in planta growth of the mutant was also significantly reduced in host tobacco leaves as compared to the wild-type strain. Thus, our results suggest that poly P plays an important role in the virulence of P. syringae pv. tabaci 6605. (C) 2008 Elsevier Ltd. All rights reserved.
• Suppression of clubroot disease under neutral pH caused by inhibition of spore germination of Plasmodiophora brassicae in the rhizosphere

  R. Niwa, Y. Nomura, M. Osaki, T. Ezawa

  PLANT PATHOLOGY 57 (3) 445 - 452 0032-0862 2008/06 [Refereed][Not invited]
   

  To elucidate the mechanism of clubroot suppression under neutral soil pH, a highly reproducible germination assay system under soil culture conditions was designed based on the hypothesis that germinated spores of Plasmodiophora brassicae could be identified by the absence of a nucleus (i.e. having released a zoospore to infect a root hair of the host plant). Brassica rapa var. perviridis seedlings were inoculated with a spore suspension of P. brassicae at a rate of 2.0 x 10(6) spores g(-1) soil and grown in a growth chamber for 7 days. The spores were recovered from rhizosphere and non-rhizosphere soils and stained with both Fluorescent Brightener 28 (cell-wall-specific) and SYTO 82 orange fluorescent nucleic-acid stain (nucleus-specific stain). Total numbers of spores were counted under UV-excitation, and spores with a nucleus that fluoresced orange under G-excitation were counted. The significant increase in the percentage of spores without a nucleus (germinated spores) in the rhizosphere after 7 days' cultivation and the correlation with root-hair infections validated the assay system. Applications of calcium-rich compost or calcium carbonate to neutralize the soil significantly reduced the percentage of germinated spores in the rhizosphere, as well as the number of root-hair infections. The present study provides direct evidence that the inhibition of spore germination is the primary cause of disease suppression under neutral soil pH.
• Increase in soil pH due to Ca-rich organic matter application causes suppression of the clubroot disease of crucifers

  Rieko Niwa, Toshiaki Kumei, Yoshinobu Nomura, Shigekata Yoshida, Mitsuru Osaki, Tatsuhiro Ezawa

  SOIL BIOLOGY & BIOCHEMISTRY 39 (3) 778 - 785 0038-0717 2007/03 [Refereed][Not invited]
   

  Clubroot disease of cruciferous plants caused by the soil-borne pathogen Plasmodiophora brassicae is difficult to control because the pathogen survives for a long time in soil as resting spores. Disease-suppressive and conducive soils were found during the long-term experiment on the impact of organic matter application to arable fields and have been studied to clarify the biotic and abiotic factors involved in the disease suppression. The fact that a large amount of organic matter, 400 t ha(-1) yr(-1) farmyard manure (FYM) or 100 t hat yr(-1) food factory sludge compost (FSC), had been incorporated for more than 15 yr in the suppressive soils and these soils showed higher pH and Ca concentration than the disease conducive soil led us to hypothesize that an increase in soil pH due to the long-term incorporation of Ca-rich organic matter might be the primary cause of the disease Suppression. We have designed a highly reproducible bioassay system to examine this hypothesis. The suppressive and conducive soils were mixed with the resting spores of P. brassicae at a rate of 10(6) spore g(-1) soil, and Brassica campestris was grown in a growth chamber for 8d. The number of root hair infections was assessed on a microscope. It was found that the incorporation of FYM and FSC at 2.5% (w/w) to the conducive soil suppressed the infection and that the finer particles (<= 5 mm) of FSC inhibited the infection and increased soil pH more effectively. Neutralization of the conducive soil by Ca(OH)(2), CaCO3 and KOH suppressed the infection, but the effectiveness of KOH was less than those of Ca(OH)(2) and CaCO3. Acidification of the Suppressive soils by H2SO4, promoted the infection. The involvement of soil biota in the disease suppression was investigated using the sterilized (gamma-ray irradiation) suppressive soils with respect to soil pH. The gamma-ray irradiation promoted the infection at pH 5.5, but no infection was observed at pH 7.4 irrespective of the sterilization status. All these observations suggest that soil pH is a major factor in disease suppression by organic matter application and that Ca and soil biota play certain roles in the suppression under the influence of soil pH. (c) 2006 Elsevier Ltd. All rights reserved.
• 菌根共生初期に増大するリン酸化シグナル(2007年度大会一般講演要旨)

  大友 量, 小島 知子, 江沢 辰広, 川口 正代司

  土と微生物 日本土壌微生物学会 61 (2) 157 - 157 2007
• 絶対寄生性アブラナ科植物根こぶ病菌のリボソームRNA遺伝子転写ユニットの構造(2006年度大会一般講演要旨)

  丹羽 理恵子, 大崎 満, 江沢 辰広

  土と微生物 日本土壌微生物学会 60 (2) 126 - 126 2006
• バイオセンサーによるアブラナ科野菜根こぶ病胞子発芽誘引物質の探索 : 來雑バクテリア由来の応答を排除した測定条件の確立(2006年度大会一般講演要旨)

  稲葉 尚子, 丹羽 理恵子, 松浦 英幸, 大崎 満, 江沢 辰広

  土と微生物 日本土壌微生物学会 60 (2) 125 - 125 2006
• Acquisition and long-distance translocation of phosphorus in the symbiotic phase of arbuscular mycorrhizal fungi

  T. Ezawa, C. Tani, Y. Kuga, R. Ohtomo

  PROCEEDINGS OF THE 8TH INTERNATIONAL MYCOLOGICAL CONGRESS 61 - + 2006 [Refereed][Not invited]
   

  Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that colonize the roots of most land plants. The main physiological basis for the mutualistic relationship is bidirectional nutrient transfer between the symbionts (Smith & Read, 1997). The host plant supplies carbon source to the fungal partner to receive P from the fungi which are able to take up and transport P more efficiently than the host. In this article, recent progresses in biochemical, molecular biological and cytochemical studies on the P metabolism and translocation in the associations are integrated.
• A new hypothesis on the strategy for acquisition of phosphorus in arbuscular mycorrhiza: Up-regulation of secreted acid phosphatase gene in the host plant

  T Ezawa, M Hayatsu, M Saito

  MOLECULAR PLANT-MICROBE INTERACTIONS 18 (10) 1046 - 1053 0894-0282 2005/10 [Refereed][Not invited]
   

  The mycorrhiza-responsive phosphatase of Tagetes patula in symbiosis with Glomus etunicatum was detected by electrophoresis, was purified by column chromatography, and was characterized as acid phosphatase that was secreted into rhizosphere. The N-terminal amino acid sequence was determined by a gas-phase sequencer, and a cDNA fragment of the phosphatase gene (TpPAP1) was amplified by degenerate primers designed based on the N-terminal amino acid sequence. The full-length cDNA was obtained by the rapid amplification of cDNA ends technique. The TpPAP1 was of host origin, and the cDNA was 1,843 bp long with a predicted open reading frame of polypeptide of 466 amino acids. Phylogenetic analysis revealed that the gene fell into the cluster of plant high-molecular-weight purple acid phosphatase. Expression analysis of the TpPAP1 in T patula in symbiosis with Archaeospora leptoticha showed that the levels of transcripts increased eightfold by mycorrhizal colonization. Western blot analysis revealed that the 57-kDa protein corresponding to the mycorrhiza-responsive phosphatase increased by mycorrhizal colonization. The present study proposes a new strategy for acquisition of P in arbuscular mycorrhizal associations in which the fungal partner activates a part of the low-P adaptation system of the plant partner, phosphatase secretion, and improves the overall efficiency of P uptake.
• 二重染色による根こぶ病菌休眠胞子の土壌中での発芽ポテンシャル評価(2005年度大会一般講演要旨)

  丹羽 理恵子, 大崎 満, 江沢 辰広

  土と微生物 日本土壌微生物学会 59 (2) 146 - 146 2005
• 酸性硫酸塩土壌に侵入したパイオニア植物に共生するアーバスキュラー菌根菌(2005年度大会一般講演要旨)

  宮川 祥江, 大崎 満, 江沢 辰広

  土と微生物 日本土壌微生物学会 59 (2) 133 - 133 2005
• アーバスキュラー菌根における物質代謝と輸送:4億年前に確立された共生システムへの温故知“最新”的アプローチ

  江沢辰広, 斎藤勝晴, 青野俊裕

  日本土壌肥料学雑誌 日本土壌肥料学会 75 (6) 737 - 746 0029-0610 2004/12/05 [Not refereed][Not invited]
  
• Quantification of polyphosphate: different sensitivities to short-chain polyphosphate using enzymatic and colorimetric methods as revealed by ion chromatography

  R Ohtomo, Y Sekiguchi, T Mimura, M Saito, T Ezawa

  ANALYTICAL BIOCHEMISTRY 328 (2) 139 - 146 0003-2697 2004/05 [Refereed][Not invited]
   

  Polyphosphate is ubiquitous and has a variety of biochemical functions. Among polyphosphate quantification methods, an enzymatic assay using Escherichia coli polyphosphate kinase (PPK), in which polyphosphate is converted to adenosine 5'-triphosphate and quantified by luciferase assay, is the most specific and most sensitive. However, chain-length specificity of the assay has not been analyzed in detail so far. Ion chromatography equipped with an on-line hydroxide eluent generator enabled us to analyze polyphosphate up to 50 inorganic phosphate (P) residues, and we employed this method to investigate the chain-length specificity of PPK in this study. Several fractions of short-chain polyphosphate were prepared by electrophoresis, and the chain-length distribution was analyzed before and after 1-6 h PPK reaction by ion chromatography. Polyphosphates longer than 23 P-i residues were processed by PPK completely after 1 h incubation, but complete processing of those between 11 and 22 P-i residues required 6 h incubation. Limited processing of polyphosphates of 10 P-i residues or shorter were observed even after 6 h incubation. Metachromasy of Toluidine blue O, an alternative method for polyphosphate quantification, showed broader chain-length specificity although it was not as sensitive as the enzymatic assay. Combination of these two methods would be practically applicable to analysis of polyphosphate dynamics in living organisms. (C) 2004 Elsevier Inc. All rights reserved.
• Rapid accumulation of polyphosphate in extraradical hyphae of an arbuscular mycorrhizal fungus as revealed by histochemistry and a polyphosphate kinase/luciferase system

  T Ezawa, TR Cavagnaro, SE Smith, FA Smith, R Ohtomo

  NEW PHYTOLOGIST 161 (2) 387 - 392 0028-646X 2004/02 [Refereed][Not invited]
   

  The rate of polyphosphate accumulation in extraradical hyphae of an arbuscular mycorrhizal fungus was investigated by conventional histochemistry and a new enzymatic method using a bacterial enzyme, polyphosphate kinase. Marigold (Tagetes patula cv. Bonanza Orange) was inoculated with Archaeospora leptoticha and grown under P-deficient conditions. Extraradical hyphae were harvested at 0, 1, 3 and 24 h after 1 mM P-application. PolyP levels were assessed by both metachromasy of Toluidine blue O and polyphosphate kinase which converted polyP to ATP followed by the ATP-luciferase assay. Percentage of hyphae with metachromatic granules was increased from 25 to 44% from 0 to 1 h, and a maximum of 50% was reach by 3 h. Polyphosphate content was doubled from 1 to 3 h after P-application (4.8-10.0 mol as Pi mg(-1) protein) at a rate of 46.4 +/- 15.1 nmol min(-1) mg(-1). The rate of polyphosphate accumulation in the hyphae was surprisingly rapid as those of polyphosphate-hyper accumulating microorganisms. The enzymatic method employed in the present study allows highly specific and sensitive assessment of polyphosphate in the mycorrhizal system.
• アブラナ科植物根こぶ病菌休眠胞子の核染色による発芽検定(2004年度大会一般講演要旨)

  丹羽 理恵子, 江沢 辰広

  土と微生物 日本土壌微生物学会 58 (2) 125 - 125 2004
• アーバスキュラー菌根菌の外生菌糸におけるポリリン酸合成・安定化に及ぼす : 細胞内遊離アミノ酸およびポリアミンの影響(2004年度大会一般講演要旨)

  森 昭暢, 寺門 純子, 藤原 伸介, 大友 量, 江沢 辰広

  土と微生物 日本土壌微生物学会 58 (2) 124 - 124 2004
• Enhancement of the effectiveness of indigenous arbuscular mycorrhizal fungi by inorganic soil amendments

  T Ezawa, K Yamamoto, S Yoshida

  SOIL SCIENCE AND PLANT NUTRITION 48 (6) 897 - 900 0038-0768 2002/12 [Refereed][Not invited]
   

  The influence of inorganic soil amendments on the effectiveness of indigenous arbuscular mycorrhizal (AM) fungi was investigated in pot experiments. Intact or ground perlite, Kanumatsuchi (volcanic ash soil), vermiculite, or rice-hull charcoal was mixed with uncultivated soil in which Glomus sp. was dominant, and marigold (Tagetes patula L.) was sown to the soil mixtures. AM colonization of the host roots increased by the incorporation of ground materials but not by that of intact materials. The growth promotive effect of the indigenous fungi on the host was enhanced by both the intact and ground materials. The inorganic materials improved the soil physical properties: the intact materials increased the gaseous phase of the media and the ground materials increased the aqueous phase. It was suggested that the inorganic soil amendments might not only provide a less-competitive habitat for the fungi but also improve the physical environment.
• P metabolism and transport in AM fungi

  T Ezawa, SE Smith, FA Smith

  PLANT AND SOIL 244 (1-2) 221 - 230 0032-079X 2002/07 [Refereed][Not invited]
   

  The arbuscular mycorrhizal symbiosis is mutualistic, based on reciprocal transfer of P from the fungus to the plant and carbon from the plant to the fungus. Thus P is a most important `currency' in the symbiosis. After absorbing P from the soil solution, the fungi first incorporate it into the cytosolic pool, and the excess P is transferred to the vacuoles. The vacuolar P pool probably plays a central role in P supply to the plant. The main forms of inorganic P in fungal vacuoles are orthophosphate and polyphosphate, but organic P molecules may also be present. Long distance translocation of P from the site of uptake in the external mycelium to the site of transfer to the plant is probably achieved via transfer of vacuolar components. This transport would be mediated either by protoplasmic streaming or the motile tubular vacuole-like system. The site of release of P into the interfacial apoplast and thence to the plant is most probably the fungal arbuscules. The biochemical and biophysical processes involved in P metabolism and transfer between cellular compartments in the symbiosis are currently not well understood. Some recent investigations of substrate specificities of phosphatase-type enzymes in AM fungi and other eukaryotic microorganisms, however, have shed new light on earlier results and permit the construction of a hypothetical scheme of P-flow, including possible regulatory factors. Steps in this scheme are experimentally testable and should stimulate future research.
• Extensive tubular vacuole system in an arbuscular mycorrhizal fungus, Gigaspora margarita

  Y Uetake, T Kojima, T Ezawa, M Saito

  NEW PHYTOLOGIST 154 (3) 761 - 768 0028-646X 2002/06 [Refereed][Not invited]
   

  A tubular vacuolar system is reported here for the first time in living hyphae of Gigaspora margarita, an arbuscular mycorrhizal fungus, during various phases in the development of a symbiotic relationship with onion (Allium cepa) seedlings. Germ tubes, extraradical hyphae and intercellular hyphae were labeled with Oregon Green 488 carboxylic acid diacetate and observed by laser scanning confocal microscopy. Emphasis was placed on the relationship between the shape of vacuoles and the presence of cytoplasmic streaming. In germ tubes, labeled vacuoles showed a variety of profiles, including spherical and tubular (< 0.5 mum diameter), with various compositions of these shapes along the length of the germ tubes. The tubular vacuoles rarely interconnected with spherical vacuoles and often formed longitudinally oriented, elongated bundles. The tubular vacuolar system appeared to be associated with cytoplasmic streaming, whereas spherical vacuoles were not. Tubular vacuoles were observed in all regions of the germ tubes and were also observed in both extraradical and intercellular hyphae. The results question the hypothesis that discrete vacuoles may be involved in the translocation of polyphosphate along hyphae of arbuscular mycorrhizal fungi. (C) New Phytologist (2002) 154: 761-768.
• Enzyme activity involved in glucose phosphorylation in two arbuscular mycorrhizal fungi: indication that polyP is not the main phosphagen

  T Ezawa, SE Smith, FA Smith

  SOIL BIOLOGY & BIOCHEMISTRY 33 (9) 1279 - 1281 0038-0717 2001/07 [Refereed][Not invited]
   

  Enzyme activity involved in glucose phosphorylation, the first step of glycolysis and the pentose phosphate pathway (PPP), in the spores, extra- and intraradical hyphae of Glomus etunicatum and G. coronatum was measured to clarify the role of polyphosphate as a phosphagen. Hexokinase, which utilizes ATP as a phosphagen was active in the all components of both fungi, suggesting that glucose can be metabolized generally through glycolysis/PPP. Polyphosphateglucakinase-type activity, in which polyphosphate is utilized as a phosphagen, was detectable in the spores and intraradical hyphae of both fungi but negligible compared with that of hexokinase. Hexokinase and polyphosphateglucokinase-type activities were characterized and it seems likely that the apparent polyphosphateglucokinase activity can be attributed to broad substrate specificity of the hexokinase. (C) 2001 Elsevier Science Ltd. All rights reserved.
• Differentiation of polyphosphate metabolism between the extra- and intraradical hyphae of arbuscular mycorrhizal fungi

  T Ezawa, SE Smith, FA Smith

  NEW PHYTOLOGIST 149 (3) 555 - 563 0028-646X 2001/03 [Refereed][Not invited]
   

  . Regulation of polyphosphate metabolism is reported in arbuscular mycorrhizal symbiosis. . Marigold (Tagetes patula) plants inoculated with Glomus coronatum or Glomus etunicatum were grown in mesh bags. Exopolyphosphatase activity in extra- and intraradical hyphae was measured and characterized. The hyphae were stained with Neutral red to show acidic vacuoles in which polyphosphate synthesis might occur. . Exopolyphosphate activity was differently expressed between the extra- and intraradical hyphae, as indicated by different pH optima; high activity was observed at pH 5.0 in the intraradical hyphae of both fungal species. K-m values were lower at neutral pH with long-chain polyphosphate, whereas acidic activity showed lower K-m with short-chain polyphosphate. Both extra- and intradical hyphae had acidic vacuoles. Polyphosphate occurred in the hyphae of the high-P, but not the low-P treatment. By contrast, exopolyphosphatase activity and vacuolar acidity were relatively constant irrespective of polyphosphate status. . The fungi have at least two different exopolyphosphatase-type enzymes which are differently expressed between extra- and intraradical hyphae; polyphosphate accumulation might be a dynamic balance between synthesis and hydrolysis.
• Species composition and spore density of indigenous vesicular-arbuscular mycorrhizal fungi under different conditions of P-fertility as revealed by soybean trap culture

  T Ezawa, K Yamamoto, S Yoshida

  SOIL SCIENCE AND PLANT NUTRITION 46 (2) 291 - 297 0038-0768 2000/06 [Refereed][Not invited]
   

  The influence of soil treatment over a period of 8 y on the species composition and spore density of indigenous VA mycorrhizal fungi was investigated in relation to phosphorus (P) accumulation. Soils were collected from an experimental field which was subjected to four different treatments: application of farmyard manure (FYM), application of chemical fertilizer (CF), no fertilizer application (NF) (mainly melon-cabbage had been cultivated), and grassland (alfalfa meadow, chemical fertilizer had been applied) (GL). P (Truog-P) shows large accumulation in the FYM- and GL-soils, 7,782 and 2,631 mg P2O5 kg(-1) soil, respectively, compared to the accumulation in the CF- and NF-soils, 790 and 101 mg P2O5 kg(-1) soil, respectively. Indigenous fungi were first multiplied by soybean trap culture prior to the observation of the fungal communities. Glomus sp. B1 was common to all of the four soils, and the number of spores was significantly higher in the NF-soil. Glomus sp. Y1 was commonly found in the FYM-, CF-, and NF-soils but not in the GL-soil. Glomus sp. R1 was dominant in the FYM-soil and not found in the other soils. Acaulospora sp. N1 was specifically dominant in the GL-soil. These results suggest that very high-P conditions may influence the species composition of the fungi.
• Polyphosphates in intraradical and extraradical hyphae of an arbuscular mycorrhizal fungus, Gigaspora margarita

  MZ Solaiman, T Ezawa, T Kojima, M Saito

  APPLIED AND ENVIRONMENTAL MICROBIOLOGY 65 (12) 5604 - 5606 0099-2240 1999/12 [Refereed][Not invited]
   

  The amount of polyphosphate in the intraradical and extraradical hyphae of Gigaspora margarita was estimated from successive extractions with trichloroacetic acid (TCA), EDTA and phenol-chloroform (PC), In the intraradical hyphae, most of the polyphosphate was present in TCA- and EDTA-soluble (short-chain and long-chain) fractions, whereas most of the polyphosphate in the extraradical hyphae was present in EDTA- and PC-soluble (long-chain and granular) fractions.
• Specific inhibitor and substrate specificity of alkaline phosphatase expressed in the symbiotic phase of the arbuscular mycorrhizal fungus, Glomus etunicatum

  T Ezawa, S Kuwahara, K Sakamoto, T Yoshida, M Saito

  MYCOLOGIA 91 (4) 636 - 641 0027-5514 1999/07 [Refereed][Not invited]
   

  Specific inhibitor and substrate specificity of alkaline phosphatase in the arbuscule of Glomus etunicatum were investigated, and the possible role of this enzyme in the symbiosis was discussed. Mycorrhizal roots of marigold (Tagetes patula) were digested by cellulase and pectinase to separate the intraradical hyphae from the root tissue, and phosphatase activity was stained at pH 8.5 and 5.0. The activity of alkaline phosphatase (pH 8.5) in arbuscules was inhibited in the presence of beryllium, whereas that of acid phosphatase (pH 5.0) was less sensitive to beryllium. Specificity and effectiveness of beryllium on the alkaline phosphatase was further confirmed using fractionated (soluble and insoluble) enzyme prepared from the separated hyphae. The soluble and insoluble alkaline phosphatases hydrolyzed phosphomonoester compounds (glucose-6-phosphate, beta-glycerophosphate, trehalose-6-phosphate and glucose 1-phosphate) but not pyrophosphate compounds (ATP and polyphosphate) which were hydrolyzed by acid phosphatase efficiently. The insoluble alkaline phosphatase showed high specific activity (on a protein basis) and high sensitivity to beryllium. Kinetic analysis of the insoluble alkaline phosphatase suggested the involvement of this enzyme in the sugar metabolism of the fungus due to lower Km values for sugar phosphate such as glucose-6-phosphate and trehalose-6-phosphate.
• COMPARISON OF PHOSPHATASE LOCALIZATION IN THE INTRARADICAL HYPHAE OF ARBUSCULAR MYCORRHIZAL FUNGI, GLOMUS SPP AND GIGASPORA SPP

  T EZAWA, M SAITO, T YOSHIDA

  PLANT AND SOIL 176 (1) 57 - 63 0032-079X 1995/09 [Refereed][Not invited]
   

  The localization of acid and alkaline phosphatases in the intraradical hyphae of the arbuscular mycorrhizal fungi, Glomus mosseae (Nicol, and Gerd.) Gerd. and Trappe (Gm), Gl. etunicatum Becker and Gerd. (Ge) and Gigaspora rosea Nicol, and Schenck (Gir) were compared. Marigold (Tagetes patula L.) and leek (Allium porrum L.) were inoculated with each of the three fungi. The mycorrhizal roots were harvested at 3, 4, 5 and 6 weeks after sowing (WAS), treated with a digestion solution containing cellulase and pectinase, and then stained for phosphatase activities at pH 5.0 and pH 8.5. The development of fungal structures in the host root was also examined. Gm formed fine-branched (mature) arbuscules only at the early phase of infection (3 to 4 WAS). Mature arbuscules of Ge and Gir were observed from the early phase (4 WAS) up to the end of experiment. At pH 5.0, the localization of the phosphatase activities of the three fungi were similar irrespective to host plant species. The activity appeared in mature arbuscules and intercellular hyphae, whereas the collapsed arbuscules were inactive. Ten millimolar NaF, an acid phosphatase inhibitor, inhibited the phosphatase activities of Gm and Ge but did not affect that of Gir. At pH 8.5, a difference among the fungal species was found in the localization of phosphatase activity while that between host species was not. The mature arbuscules were also the active sites in all three species. Only Gir showed the activity in the intercellular hyphae while the two Glomus spp. did not. Five millimolar EDTA inhibited the activity of Gir at pH 8.5 while the activities of Ge and Gm were not affected by either 5 mM EDTA or 10 mM KCN (both are alkaline phosphatase inhibitors).
• Compatibility between host and arbuscular mycorrhizal fungi, and influence of host plant species on the competition among the fungi

  Ezawa Tatsuhiro, Kuwahara Shinya, Yoshida Tomio

  Soil Microorganisms 日本土壌微生物学会 45 9 - 19 1995 [Refereed][Not invited]
   

  The compatibility between host and arbuscular mycorrhizal fungi and the influence of host species on the competition among the fungi were investigated in a pot experiment. Marigold, soybean and asparagus were inoculated with one (noncompetitive conditions) or three (competitive conditions) species of arbuscular mycorrhizal fungi, Glomus etunicatum (Ge), G. mosseae (Gm) and Gigaspora sp. Cl (Cl), and cultivated in a greenhouse for 77-134 days. The dry weight of the plants, the percentage of infected root length and the number of spores of each fungus were determined, The compatibility was evaluated based on the mycorrhizal growth promotion in host plant and fungal proliferation under non-competitive conditions. The growth of all the plant species was promoted by the inoculation of Ge and Gm, whereas no growth promotion was observed in the plants inoculated with Cl. The most suitable plant species for the proliferation (spread of infection and sporulation) of individual fungus was different among these three fungi. The influence of host plant species on the competition among the three fungi (Ge, Gm and Cl) was evaluated by comparing the spore number of each fungus under competitive conditions and that under non-competitive conditions. In the rhizosphere of marigold, the competitive ability of the three fungi was almost even, while the rhizosphere of soybean and asparagus, only Ge was competitive and became dominant.
• ACID-PHOSPHATASE SPECIFIC TO ARBUSCULAR MYCORRHIZAL INFECTION IN MARIGOLD AND POSSIBLE ROLE IN SYMBIOSIS

  T EZAWA, T YOSHIDA

  SOIL SCIENCE AND PLANT NUTRITION 40 (4) 655 - 665 0038-0768 1994/12 [Refereed][Not invited]
   

  The origin and properties of the phosphatase specific to the arbuscular mycorrhizal infection in marigold were investigated. Three cultivars of marigold( Tagetes spp. cv. Bonanza Spray, cv. Disco and cv. Discovery) were inoculated with Glomus etunicatum Becker & Gerd. Marigold cv. Bonanza Spray was inoculated with G. etunicatum, G. mosseae (Nicol. & Gerd.) Gerd. and Trappe or Gigaspora spp. C1. Soluble phosphatases were extracted from 6-week-old plants and subjected to electrophoretical analysis. The infection-specific phosphatases (ISPases) were commonly detected in all these associations, and their Rf values were almost the same (0.11-0.12). A weak phosphatase activity was observed at the same Rf value as that of ISPase in the non-mycorrhizal plant. No major phosphatase band was observed at Rf 0.11-0.12 in the extracts of germinating and resting spores of G. etunicatum. These observations suggest that the ISPase is of host origin. The ISPase was partially purified from the roots of cv. Bonanza Spray infected with G. etunicatum about 170-fold, and characterized. The optimum pH at 5.0, the hydrolysis of various phosphate esters and the inhibition by fluoride, molybdate, phosphate, and vanadate were indicative of the typical characteristics of non-specific acid phosphatase (E.C. 3.1.3.2). In addition, since the enzyme hydrolyzed the pyrophosphate bond effectively, it is suggested that the enzyme is an acid phosphatase originating from the plant. The possible role of ISPase in the mycorrhizal symbiosis is discussed.
• CHARACTERIZATION OF PHOSPHATASE IN MARIGOLD ROOTS INFECTED WITH VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI

  T EZAWA, T YOSHIDA

  SOIL SCIENCE AND PLANT NUTRITION 40 (2) 255 - 264 0038-0768 1994/06 [Refereed][Not invited]
   

  The phosphatase specific to the infection of vesicular-arbuscular mycorrhizal fungi (Glomus etunicatum Becker & Gerdemann) in marigold (Tagetes patula L.) roots was investigated in relation to the mycorrhizal growth promotion in host plant. Mycorrhizal and non-mycorrhizal marigold plants were cultured in a growth chamber, and the enzyme solution was extracted from 2- to 10-week-old plant roots. The infection-specific phosphatase (ISPase) was detected in the mycorrhizal root extract from the beginning of the infection (4-week-old plant) by an electrophoretical technique. The activity increased as the infection rate increased, and decreased at the stationary phase of the host growth when the infection rate was still high. The effect of phosphorus (P) fertilization on the ISPase activity and the mycorrhizal growth promotion in host was investigated in 4- to 8-week-old plants using two kinds of liquid fertilizers with different P concentrations. The plants without P-fertilization showed more increase in the shoot fresh weight (SFW) of mycorrhizal plant and higher ISPase activity than the plant with P supply. The integrated values of the ISPase activity (from 0 to given week) were highly correlated with the increase in the SFW of the mycorrhizal plant. The ISPase was partially purified by ammonium sulfate, hydrophobic chromatography, and gel filtration, and characterized as follows: the optimum pH was 7.5, 1 mM phosphate ion inhibited half of the activity, the enzyme hydrolyzed inosine 5'-diphosphate effectively and polyphosphate moderately. The possibility of using ISPase as an indicator for the growth response of mycorrhizal plants and the metabolic role of this enzyme were discussed.

MISC

• 葉の遺伝子発現による地下微生物機能の診断

  江沢辰広, 杉村悠作, 丸山隼人  日本土壌肥料学会講演要旨集(Web)  67-  2021
• コムギにおける菌根特異的遺伝子群のゲノム内重複と発現制御機構の保存性

  坂上桃花, 青山奈央, 杉原創, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  67-  2021
• 農耕地利用の強度に応答したアーバスキュラー菌根菌群集の収斂と多様性の維持機構

  丹羽理恵子, 佐藤修正, 佐藤修正, 平川英樹, 吉田重信, 佐藤孝, 鈴木貴恵, 佐藤匠, 俵谷圭太郎, 福永亜矢子, 小八重善裕, 大友量, 林正紀, 唐澤敏彦, 神山拓也, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  66-  2020
• 菌根経路からのリン酸獲得により発現誘導される植物の樹枝状体形成遺伝子群

  浅枝諭史, 杉村悠作, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  65-  2019
• 野外における植物・菌根菌の環境応答-フィールドトランスクリプトミクスが語る頑強かつ柔軟な制御-

  杉村悠作, 河原愛, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  65-  2019
• アーバスキュラー菌根菌Rhizophagus clarusにおける生態型分化:地理的隔離株間における酸性応答遺伝子群の極端な不一致

  中西夏輝, LI Tingting, 杉村悠作, 俵谷圭太郎, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  65-  2019
• 菌根形成植物のリン酸獲得トレードオフを制御する分子ネットワーク

  丸山隼人, 港翔平, 杉村悠作, 手塚あゆみ, 永野惇, 江澤辰広  日本土壌肥料学会講演要旨集(Web)  65-  2019
• 農耕地管理強度に沿ったアーバスキュラー菌根菌群集の入れ子構造:その生存戦略とインパクト

  丹羽理恵子, 佐藤修正, 佐藤修正, 平川英樹, 吉田重信, 佐藤孝, 鈴木貴恵, 佐藤匠, 俵谷圭太郎, 福永亜矢子, 小八重善裕, 大友量, 林正紀, 唐澤敏彦, 神山拓也, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集(Web)  65-  2019
• 菌根菌叢・細菌叢同定ウェブインターフェースの開発

  平川英樹, 丹羽理恵子, 佐藤修正, 江沢辰広  日本植物細胞分子生物学会大会・シンポジウム講演要旨集  37th-  2019
• 3-1-7 アーバスキュラー菌根菌Rhizophagus clarusにおける生態型分化：地理的隔離株間における酸性応答遺伝子群の極端な不一致（3-1 土壌生物の生態と機能，2019年静岡大会）

  中西 夏輝, Li Tingting, 杉村 悠作, 俵谷 圭太郎, 丸山 隼人, 江沢 辰広  日本土壌肥料学会講演要旨集  65-  (0)  24  -24  2019  [Not refereed][Not invited]
  
• 3-1-9 野外における植物・菌根菌の環境応答 －フィールドトランスクリプトミクスが語る頑強かつ柔軟な制御－（3-1 土壌生物の生態と機能，2019年静岡大会）

  杉村 悠作, 河原 愛, 丸山 隼人, 江沢 辰広  日本土壌肥料学会講演要旨集  65-  (0)  24  -24  2019  [Not refereed][Not invited]
  
• 3-1-10 菌根経路からのリン酸獲得により発現誘導される植物の樹枝状体形成遺伝子群（3-1 土壌生物の生態と機能，2019年静岡大会）

  浅枝 諭史, 杉村 悠作, 丸山 隼人, 江沢 辰広  日本土壌肥料学会講演要旨集  65-  (0)  25  -25  2019  [Not refereed][Not invited]
  
• 4-1-10 菌根形成植物のリン酸獲得トレードオフを制御する分子ネットワーク（4-1 植物の多量栄養素，2019年静岡大会）

  丸山 隼人, 港 翔平, 杉村 悠作, 手塚 あゆみ, 永野 惇, 江澤 辰広  日本土壌肥料学会講演要旨集  65-  (0)  44  -44  2019  [Not refereed][Not invited]
  
• 3-1-8 農耕地管理強度に沿ったアーバスキュラー菌根菌群集の入れ子構造：その生存戦略とインパクト（3-1 土壌生物の生態と機能，2019年静岡大会）

  丹羽 理恵子, 小八重 善裕, 大友 量, 林 正紀, 唐澤 敏彦, 神山 拓也, 丸山 隼人, 江沢 辰広, 佐藤 修正, 平川 英樹, 吉田 重信, 佐藤 孝, 鈴木 貴恵, 佐藤 匠, 俵谷 圭太郎, 福永 亜矢子  日本土壌肥料学会講演要旨集  65-  (0)  24  -24  2019  [Not refereed][Not invited]
  
• 菌根菌叢および細菌叢のウェブ上解析インターフェースの開発

  平川英樹, 丹羽理恵子, 佐藤修正, 江沢辰広  日本ゲノム微生物学会年会要旨集  12th-  2018
• 現地農家圃場等におけるネギへのAM菌資材の接種効果

  鈴木貴恵, 丹羽理恵子, 丹羽理恵子, 宇野亨, 田島亮介, 伊藤豊彰, 伊藤豊彰, 佐藤修正, 平川英樹, 吉田重信, 江沢辰広, 齋藤雅典, 齋藤雅典  日本土壌肥料学会講演要旨集  64-  2018
• P3-1-10 菌根経路を介したポリリン酸長距離輸送・リン酸移行の分子機構（ポスター，3-1 土壌生物の生態と機能，2018年度神奈川大会）

  浅枝 諭史, 丸山 隼人, 江沢 辰広  日本土壌肥料学会講演要旨集  64-  (0)  37  -37  2018  [Not refereed][Not invited]
  
• 3-1-16 菌根形成植物における有機態リン獲得の分子機構（ミニシンポジウム，3-1 土壌生物の生態と機能，2018年度神奈川大会）

  丸山 隼人, 中西 夏輝, 浅枝 諭史, 杉村 悠作, 江沢 辰広  日本土壌肥料学会講演要旨集  64-  (0)  31  -31  2018  [Not refereed][Not invited]
  
• 3-1-24 野外における菌根形成制御機構 －生態トランスクリプトーム解析によるアプローチ－（3-1 土壌生物の生態と機能，2018年度神奈川大会）

  杉村 悠作, 河原 愛, 丸山 隼人, 江沢 辰広  日本土壌肥料学会講演要旨集  64-  (0)  33  -33  2018  [Not refereed][Not invited]
  
• 4-1-2 植物のトランスクリプトーム応答を利用した直接および菌根経路からのリン獲得量の推定（4-1 植物の多量栄養素，2018年度神奈川大会）

  港 翔平, 丸山 隼人, 手塚 あゆみ, 永野 惇, 江沢 辰広  日本土壌肥料学会講演要旨集  64-  (0)  45  -45  2018  [Not refereed][Not invited]
  
• 4-1-1 菌根形成植物におけるリン栄養応答遺伝子のネットワーク解析（4-1 植物の多量栄養素，2018年度神奈川大会）

  丸山 隼人, 杉村 悠作, 手塚 あゆみ, 永野 惇, 江沢 辰広  日本土壌肥料学会講演要旨集  64-  (0)  45  -45  2018  [Not refereed][Not invited]
  
• Estimation of phosphate acquisition through the mycorrhizal pathway via transcriptome responses in Nicotiana benthamiana

  MARUYAMA Hayato, TEZUKA Ayumi, NAGANO Atsushi J, EZAWA Tatsuhiro  日本植物生理学会年会(Web)  59th-  ROMBUNNO.P.335  2018  [Not refereed][Not invited]
  
• 菌根経路からのリン酸獲得に対する植物の特異的トランスクリプトーム応答

  丸山隼人, 手塚あゆみ, 永野惇, 江沢辰広  日本土壌肥料学会講演要旨集  63-  49  2017/09/05  [Not refereed][Not invited]
  
• 直接および菌根経路からのリン酸獲得に対するトランスクリプトーム応答―ネギにおける解析精度向上を目的としたリファレンス整備―

  港翔平, 丸山隼人, 手塚あゆみ, 永野惇, 江沢辰広  日本土壌肥料学会講演要旨集  63-  58  2017/09/05  [Not refereed][Not invited]
  
• アーバスキュラー菌根菌接種の残効が翌年のダイズ生育へ及ぼす影響

  神山拓也, 丹羽理恵子, 安達克樹, 江沢辰広, 鈴木崇之, 佐藤修正, 佐藤修正, 平川英樹, 吉田重信  日本作物学会講演会要旨集  243rd-  189  2017/03/29  [Not refereed][Not invited]
  
• 耐酸性アーバスキュラー菌根菌との共生による植物の耐酸性獲得とその分子メカニズム

  中西夏輝, 杉村悠作, 丸山隼人, 江沢辰広  日本土壌肥料学会講演要旨集  63-  2017
• 菌根共生による植物耐酸性の限界突破...そんなに単純じゃない:第三のプレーヤー候補マイコウィルス

  江沢辰広, 河原愛, 鈴木芽以, 中西夏輝, 丸山隼人, 増田税  日本微生物生態学会大会(Web)  2017-  2017
• 4-3-20 耐酸性アーバスキュラー菌根菌との共生による植物の耐酸性獲得とその分子メカニズム（4-3 植物の有害元素，2017年度仙台大会）

  中西 夏輝, 杉村 悠作, 丸山 隼人, 江沢 辰広  日土肥講要  63-  (0)  76  -76  2017  [Not refereed][Not invited]
  
• アーバスキュラー菌根菌から宿主へのリン酸供給機構:PHO1リン酸排出輸送体の機能

  丸山隼人, 横山楓, 菊池裕介, 中西夏輝, 阿部歩, 曾根輝雄, 斎藤勝春, 増田税, 江沢辰広  日本土壌肥料学会講演要旨集  62-  30  2016/09/20  [Not refereed][Not invited]
  
• ネギにおけるアーバスキュラー菌根菌接種菌と土着菌との競合および接種効果発現に関わる環境要因

  丹羽理恵子, 丸山隼人, 佐藤修正, 佐藤修正, 平川英樹, 吉田重信, 齋藤雅典, 齋藤雅典, 鈴木貴恵, 俵谷圭太郎, 佐藤匠, 江沢辰広  日本土壌肥料学会講演要旨集  62-  29  2016/09/20  [Not refereed][Not invited]
  
• アーバスキュラー菌根菌接種資材の作物根への定着に関わる生態的要因

  丹羽理恵子, 丸山隼人, 佐藤修正, 平川英樹, 吉田重信, 大友量, 小八重善裕, 佐藤孝, 唐澤敏彦, 林正紀, 福永亜矢子, 安達克樹, 神山拓也, 江沢辰広  日本土壌微生物学会講演要旨集  2016-  57  2016/06/06  [Not refereed][Not invited]
  
• P3-1-6 低リン条件におけるアーバスキュラー菌根菌Rhizophagus clarusの外生菌糸による酸性ホスファターゼの浸出(ポスター,3-1 土壌生物の生態と機能,2015年度京都大会)

  佐藤 匠, 江沢 辰広, 程 為国, 俵谷 圭太郎  日本土壌肥料学会講演要旨集  (61)  35  -35  2015/09/09
• 4-1-22 アーバスキュラー菌根におけるリン酸長距離輸送の駆動力を伝える共生菌水輸送体(4-1 植物の多量栄養素,2015年度京都大会)

  菊池 裕介, 斎藤 勝晴, 大友 量, 川口 正代司, 増田 税, 江沢 辰広  日本土壌肥料学会講演要旨集  (61)  55  -55  2015/09/09
• 4 蛇紋岩土壌におけるアーバスキュラー菌根菌の群集構造は特有の土壌要因により特殊化されない(北海道支部講演会,2013年度各支部会)

  渡邉 ゆか, 園田 順, 河原 愛, 江沢 辰広  日本土壌肥料学会講演要旨集  (60)  243  -243  2014/09/09
• 3-1-13 メタ解析から見えてきた農耕地に特化したアーバスキュラー菌根菌分類群(3-1 土壌生物の生態と機能,2014年度東京大会)

  荒川 竜太, 江沢 辰広  日本土壌肥料学会講演要旨集  (60)  33  -33  2014/09/09
• S3-1-19 アーバスキュラー菌根菌におけるウイルス共生体の起源とインパクト : メタゲノムアプローチ(ミニシンポジウム S3-1,3-1 土壌生物の生態と機能,2014年度東京大会)

  江沢 辰広, 池田 庸二, 志村 華子, 増田 税  日本土壌肥料学会講演要旨集  (60)  35  -35  2014/09/09
• P3-1-13 菌根共生で誘導されるパープル酸性ホスファターゼLjPAP3の生化学特性(ポスター,3-1 土壌生物の生態と機能,2014年度東京大会)

  吉村 侑子」, 間瀬 ひろみ, 齋藤 雅典, 江沢 辰広, 齋藤 勝晴  日本土壌肥料学会講演要旨集  (60)  40  -40  2014/09/09
• 4-1-22 トランスクリプトームのリン応答性から構築されるアーバスキュラー菌根菌のリン酸吸収・代謝・輸送機構の全体像(4-1 植物の多量栄養素,2014年度東京大会)

  菊池 裕介, 横山 楓, 土方 野分, 大友 量, 半田 佳宏, 川口 正代司, 齋藤 勝晴, 江沢 辰広  日本土壌肥料学会講演要旨集  (60)  54  -54  2014/09/09
• 菌根共生からみる植物栄養の新時代

  小八重善裕, 東樹宏和, 山本哲史, 竹本大吾, 江沢辰広, 河原愛, 荒川竜太, 齋藤勝晴, 中川知己  日本土壌肥料学雑誌  85-  (3)  279  -284  2014/06/05  [Not refereed][Not invited]
   

  農業生産と環境負荷低減の両立を図る取り組みとして，菌根共生を活用した植物栽培に期待がもたれる。草本木本を問わず，多くの植物は根でアーバスキュラー菌根菌(AM菌)や外生菌根菌と共生しており，土壌に広く伸びた菌糸を使って養分を効率よく吸収する。植物種と菌種の組み合わせの検討や，菌根の養分吸収機構の解明，収量増につながる分子機構などを明らかにすることは，植物に効率よく肥料を取り込ませ，肥料の節減を図るためにも重要である。しかし実際の生態系で機能する菌根の種類は膨大であり，またその生態や生理にも不明な点が多い。どのようにして菌根を活用・運用することが，植物生産にとって望ましいのか，明確な道筋は見えていない。ところが近年，バイオインフォマティクスを使った研究が非常に有効になってきており，実際の圃場や森林に形成される菌根の植物種，菌種，遺伝子発現，分子間相互作用など，これまで追跡が困難であった菌根の複雑な生態とその動態，さらには養分輸送を含めた生理的な振る舞いまでもが，in silicoで予測出来るようになる可能性を感じさせる。
• P25-22 アーバスキュラー菌根菌の内生菌糸と外生菌糸のRNA-seq解析(ポスター発表)

  杉村 悠作, 半田 佳宏, 菊地 裕介, 江沢 辰広, 川口 正代司, 齋藤 勝晴  日本微生物生態学会講演要旨集  2014-  249  -249  2014
• II-5 アーバスキュラー菌根菌におけるBaas Becking仮説の検証 : 多重環境フィルタを生き抜く「最強ジェネラリスト」存在の可能性(II 菌根共生からみる植物栄養の新時代,シンポジウム,2013年度名古屋大会)

  江沢 辰広, 河原 愛, 荒川 竜太  日本土壌肥料学会講演要旨集  (59)  208  -208  2013/09/11
• P3-1-23 アーバスキュラー菌根菌の外生菌糸が浸出する酸性ホスファターゼ活性の低リン条件下における応答(ポスター,3-1 土壌生物の生態と機能,2013年度名古屋大会)

  佐藤 匠, 程 為国, 江沢 辰広, 俵谷 圭太郎  日本土壌肥料学会講演要旨集  (59)  47  -47  2013/09/11
• P3-1-2 ウイルス誘導性遺伝子サイレンシングを用いたアーバスキュラー菌根菌の菌糸内リン酸輸送解析(ポスター,3-1 土壌生物の生態と機能,2013年度名古屋大会)

  菊池 裕介, 内尾 圭文, 齋藤 勝晴, 増田 税, 江沢 辰広  日本土壌肥料学会講演要旨集  (59)  40  -40  2013/09/11
• 3-1-11 桜島降灰地における植生発達段階とアーバスキュラー菌根菌群集の撹乱耐性(3-1 土壌生物の生態と機能,2013年度名古屋大会)

  工藤 史帆, 河原 愛, 菊池 裕介, 荒川 竜太, 田中 淳, 佐藤 亜貴夫, 江沢 辰広  日本土壌肥料学会講演要旨集  (59)  37  -37  2013/09/11
• 4-3-5 アルミニウム耐性植物ススキのリン酸吸収を担う直接および菌根経路 : 遺伝子発現および系統解析から推定するリン酸輸送体遺伝子の機能分化(4-3 植物の有害元素)

  佐藤 理子, 菊池 裕介, 河原 愛, 江沢 辰広  日本土壌肥料学会講演要旨集  (59)  76  -76  2013/09/11
• 4-3-6 アルミニウム耐性植物ススキのリン酸吸収を担う直接および菌根経路 : 強酸性土壌におけるリン酸輸送体遺伝子群の発現と菌根経路の重要性(4-3 植物の有害元素)

  河原 愛, 佐藤 理子, 江沢 辰広  日本土壌肥料学会講演要旨集  (59)  76  -76  2013/09/11
• P4-1-13 菌根菌に対する受容性が異なるトウモロコシ品種における菌根/リン応答性とストリゴラクトン分泌特性(4-1 植物の多量栄養素)

  荒川 竜太, 米山 香織, 小林 創平, 米山 弘一, 江沢 辰広  日本土壌肥料学会講演要旨集  (59)  2013/09/11  [Not refereed][Not invited]
  
• 8-5 菌根誘導性パープル酸性ホスファターゼのRNAi系統を用いたポリリン酸局在解析(8.共生,2012年度鳥取大会)

  齋藤 勝晴, 名切 孝介, 松本 忠大, 齋藤 雅典, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  47  -47  2012/09/04
• 8-9 植生回復に伴う土壌生成がアーバスキュラー菌根菌の生態および生理機能に及ぼす影響 : 西オーストラリアにおける固有種を用いた採石跡地の修復プロジェクト(8.共生,2012年度鳥取大会)

  若槻 由加, 河原 愛, Ruthrof Katinka, Dell Bernard, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  48  -48  2012/09/04
• 8-4 アーバスキュラー菌根菌におけるポリリン酸超集積 : 無機イオン輸送およびエネルギー供給に関わる遺伝子群の網羅的解析(8.共生,2012年度鳥取大会)

  菊池 裕介, 谷 千春, 土方 野分, 半田 佳宏, 川口 正代司, 斎藤 勝晴, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  47  -47  2012/09/04
• 8-10 多様なウィルスを保持するアーバスキュラー菌根菌Glomus sp.RF1株 : 2.6kb-RNAウィルスのゲノム構造と系統進化学的位置(8.共生,2012年度鳥取大会)

  北原 涼子, 池田 庸二, 志村 華子, 増田 税, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  49  -49  2012/09/04
• 8-6 耐酸性アーバスキュラー菌根菌は広範な環境に分布するジェネラリストであるフィールド調査およびモデル実験の統合(8.共生,2012年度鳥取大会)

  河原 愛, 安 起弘, 宮川 祥江, 園田 順, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  47  -47  2012/09/04
• 32 蛇紋岩土壌の初期植生におけるアーバスキュラー菌根菌の生態特徴的群集構造とその規定要因(北海道支部講演会,2011年度各支部会)

  園田 順, 河原 愛, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (58)  248  -248  2012/09/04
• 31 Ninety-year-but not temporal application of chemical fertilizer has a significant impact on the diversity and community composition of arbuscular mycorrhizal fungi

  Cheng Ying, Ishimoto Keiko, Kuriyama Yuko, Osaki Mitsuru, Ezawa Tatsuhiro  Abstracts of the meeting, the Society of the Science of Soil and Manure  (58)  248  -248  2012/09/04
• Recent advances in research on arbuscular mycorrhizal fungi and its contribution to the fields of soil science and plant nutrition

  SAKAMOTO Kazunori, AKIYAMA Kohki, HAYASHI Hideo, ISOBE Katsutaka, EZAWA Tatsuhiro, KIKUCHI Yusuke, HIJIKATA Nowaki, TAWARAYA Keitarou, IZU Susumu, SAITO Katsuharu  Japanese Journal of Soil Science and Plant Nutrition  83-  (2)  216  -221  2012  [Not refereed][Not invited]
  
• 8-4 菌根共生で誘導されるパープル酸性ホスファターゼLjPAP3の局在解析(8.共生)

  上原 洋平, 江沢 辰広, 斎藤 勝晴  日本土壌肥料学会講演要旨集  (57)  50  -50  2011/08/08
• 8-5 アーバスキュラー菌根菌のリン酸輸送における蒸散の重要性 : 宿主の蒸散速度に比例した菌糸内リン酸輸送(8.共生)

  菊池 裕介, 土方 野分, 谷 千春, 大友 量, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (57)  50  -50  2011/08/08
• 8-3 菌根形成した植物の根圏における酸性ホスファターゼ活性の検出(8.共生)

  佐藤 匠, 松田 健一郎, 江沢 辰広, 程 為国, 俵谷 圭太郎  日本土壌肥料学会講演要旨集  (57)  49  -49  2011/08/08
• 33 アーバスキュラー菌根菌群集の低温レスポンスに及ぼす土地利用形態の影響(北海道支部講演会,2010年度各支部会講演要旨)

  阿久澤 拓己, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (57)  296  -296  2011/08/08
• 11-31 植物におけるアルミニウム耐性のブレークスルー : 養分吸収の代替経路を提供する耐酸性アーバスキュラー菌根菌(11.植物の有害元素)

  河原 愛, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (57)  89  -89  2011/08/08
• トウモロコシにおけるストリゴラクトン類分泌プロファイルは共生・寄生生物の受容性と関係する

  石本圭子, 米山香織, 小林創平, 信濃卓郎, 大崎満, 横田孝雄, 米山弘一, 江沢辰広  日本土壌肥料学会講演要旨集  57-  297  2011/08/08  [Not refereed][Not invited]
  
• P8-4 菌根菌感染により発現上昇するミヤコグサパープルホスファターゼ遺伝子(ポスター紹介,8.共生,2010年度北海道大会)

  西村 あおい, 江沢 辰広, 斎藤 勝晴  日本土壌肥料学会講演要旨集  (56)  53  -53  2010/09/07
• 8-14 アーバスキュラー菌根菌の保持する新規マイコウイルス : ゲノム構造と系統進化学的位置(8.共生,2010年度北海道大会)

  池田 庸二, 志村 華子, 大崎 満, 松元 直幸, 増田 税, 江澤 辰広  日本土壌肥料学会講演要旨集  (56)  48  -48  2010/09/07
• 8-4 蛇紋岩土壌におけるアーバスキュラー菌根菌の生態 : 土壌化学性が群集構造に及ぼす影響(8.共生,2010年度北海道大会)

  園田 順, 河原 愛, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (56)  45  -45  2010/09/07
• 8-7 アーバスキュラー菌根菌における宿主方向へのリン酸輸送 : ポリリン酸輸送の駆動力としての蒸散(8.共生,2010年度北海道大会)

  菊池 裕介, 土方 野分, 大友 量, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (56)  46  -46  2010/09/07
• 8-11 土壌酸性度はアーバスキュラー菌根菌群集に対する強力な選択圧として作用する(8.共生,2010年度北海道大会)

  河原 愛, 安 起弘, 宮川 祥江, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (56)  47  -47  2010/09/07
• 8-9 根寄生植物ストライガ耐性および感受性トウモロコシが分泌するストリゴラクトンへのアーバスキュラー菌根菌群の感染応答(8.共生,2010年度北海道大会)

  石本 圭子, 米山 香織, 大崎 満, 横田 孝雄, 米山 弘一, 江沢 辰広  日本土壌肥料学会講演要旨集  (56)  2010/09/07  [Not refereed][Not invited]
  
• トウモロコシにおけるアーバスキュラー菌根菌感染率の品種・系統間差

  小林創平, 安起弘, 村木正則, 唐澤敏彦, 江澤辰広, 濃沼圭一, 信濃卓郎  研究成果情報 北海道農業  2009-  206  -207  2010/06/30  [Not refereed][Not invited]
  
• 8-2 パイオニア植物におけるアーバスキュラー菌根形成は内生細菌のnifH遺伝子発現および窒素獲得を増加させる(8.共生,2010年度北海道大会)

  蔭山 千寿, 荒川 竜太, 中島 泰弘, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  56-  (0)  44  -44  2010  [Not refereed][Not invited]
  
• P8-2 アーバスキュラー菌根菌の外生菌糸による酸性ホスファターゼの分泌(ポスター紹介,8.共生,2009年度京都大会)

  松田 健一郎, 三橋 渉, 江沢 辰広, 我妻 忠雄, 俵谷 圭太郎  日本土壌肥料学会講演要旨集  (55)  64  -64  2009/09/15
• 8-22 アーバスキュラー菌根菌におけるポリリン酸代謝 : 潜在的蓄積能とその電荷バランス調節メカニズム(8.共生,2009年度京都大会)

  土方 野分, 村瀬 正剛, 谷 千春, 大友 量, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (55)  62  -62  2009/09/15
• 8-26 アーバスキュラー菌根菌Glomus spp.におけるマイコウイルスの発見(8.共生,2009年度京都大会)

  池田 庸二, 大崎 満, 増田 税, 江沢 辰広  日本土壌肥料学会講演要旨集  (55)  63  -63  2009/09/15
• 8-24 アーバスキュラー菌根菌感染に応答するミヤコグサ酸性ホスファターゼ遺伝子の探索(8.共生,2009年度京都大会)

  西村 あおい, 鈴木 伊作, 江沢 辰広, 斎藤 勝晴  日本土壌肥料学会講演要旨集  (55)  62  -62  2009/09/15
• 8-16 リン酸施肥はアーバスキュラー菌根菌群集の規定要因となりうるか? : 90年連用圃場を利用したトラップカルチャーによる検証(8.共生,2009年度京都大会)

  石本 圭子, Cheng Ying, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (55)  60  -60  2009/09/15
• P8-4 共生菌からのリン酸移行の抑制がアーバスキュラー菌根における宿主/菌遺伝子群の発現に及ぼす影響(ポスター紹介,8.共生,2008年度愛知大会)

  青野 俊裕, 江澤 辰広  日本土壌肥料学会講演要旨集  (54)  65  -65  2008/09/09
• 8-10 アーバスキュラー菌根菌群集の低温レスポンスに及ぼす土地利用形態の影響(8.共生,2008年度愛知大会)

  阿久澤 拓己, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (54)  60  -60  2008/09/09
• 8-9 海岸砂丘におけるアーバスキュラー菌根菌の群集構造 : 植生および土壌理化学性との関係(8.共生,2008年度愛知大会)

  河原 愛, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (54)  59  -59  2008/09/09
• 8-14 酸性硫酸塩土壌に自生するパイオニア植物内生細菌のnifH mRNAの多様性(8.共生,2008年度愛知大会)

  蔭山 千寿, 荒川 竜太, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (54)  61  -61  2008/09/09
• 7-7 アブラナ科植物根こぶ病菌のrDNAにおける多型領域の同定と地理的隔離株識別の可能性(7.土壌病害,2008年度愛知大会)

  丹羽 理恵子, 田中 秀平, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (54)  56  -56  2008/09/09
• 9-1 Ionomics study of Lotus japonicus reveals the element homeostasis network in plants

  Quadir Quazi Forhad  Abstracts of the Annual Meetings, Japanese Society of Soil Science and Plant Nutrition  54-  (0)  70  -70  2008  [Not refereed][Not invited]
  
• 6 高Ca有機物の連用によるアブラナ科植物根こぶ病抑止メカニズム : pH上昇によるPlasmodiophora brassicaeの発芽阻害(北海道支部講演会,2006年度各支部会)

  丹羽 理恵子, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (53)  228  -228  2007/08/22
• 10 90年間のリン酸肥料の連用がアーバスキュラー菌根菌の群集構造と宿主生育促進能に及ぼす影響(北海道支部講演会,2006年度各支部会)

  栗山 裕子, 大崎 満, 江澤 辰広  日本土壌肥料学会講演要旨集  (53)  230  -230  2007/08/22
• 8-19 Community structures of arbuscular mycorrhizal fungi in the pioneer vegetation of acid sulfate soils : soil pH as a major determinant of community

  Gihong An, Miyakawa Sachie, Osaki Mitsuru, Ezawa Tatsuhiro  Abstracts of the meeting, the Society of the Science of Soil and Manure  (53)  58  -58  2007/08/22
• 7-1 高Ca有機物の連用によるアブラナ科植物根こぶ病抑止メカニズム : pH上昇によるPlasmodiophora brassicaeの発芽阻害(7.土壌病害,2007年度東京大会)

  丹羽 理恵子, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (53)  49  -49  2007/08/22
• 8-21 アーバスキュラー菌根菌におけるポリリン酸合成および輸送ポテンシャル(8.共生,2007年度東京大会)

  村瀬 正剛, 谷 千春, 大友 量, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (53)  58  -58  2007/08/22
• P9-33 Ion-profile variations of Lotus japonicus wild lines under 9 elements treatment in subtoxic levels

  Zheng Chen  Abstracts of the meeting, the Society of the Science of Soil and Manure  (53)  87  -87  2007/08/22  [Not refereed][Not invited]
  
• 8-20 アーバスキュラー菌根共生によるAl感受性植物の耐酸性付与のメカニズム(8.共生,2007年度東京大会)

  稲葉 尚子, 渡部 敏裕, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  53-  (0)  2007  [Not refereed][Not invited]
  
• 8-3 90年間の三要素化学肥料の連用がアーバスキュラー菌根菌の群集構造に及ぼす影響(8. 共生, 2006年度秋田大会講演要旨)

  栗山 裕子, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (52)  41  -41  2006/09/05
• P8-4 アーバスキュラー菌根菌におけるポリリン酸合成オルガネラの分画(8. 共生, 2006年度秋田大会講演要旨)

  谷 千春, 大友 量, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (52)  47  -47  2006/09/05
• 8-2 Al超集積性植物 Melastoma spp. (ノボタン属植物) の生育およびAl吸収におけるアーバスキュラー菌根共生の役割(8. 共生, 2006年度秋田大会講演要旨)

  稲葉 尚子, 渡部 敏裕, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  52-  (0)  2006  [Not refereed][Not invited]
  
• 7-3 核染色による根こぶ病菌休眠胞子のアブラナ科寄主根圏における動態観察(7.土壌病害,日本土壌肥料学会 2005年度大会講演要旨集)

  丹羽 理恵子, 大崎 満, 江沢 辰広  日本土壌肥料学会講演要旨集  (51)  48  -48  2005/09/06
• 1 蘭越町の酸性硫酸塩土壌に侵入したパイオニア植物における菌根菌感染評価(北海道支部講演会,日本土壌肥料学会 支部講演会講演要旨集 2005年度)

  宮川 祥江, 江沢 辰広, 大崎 満  日本土壌肥料学会講演要旨集  (51)  233  -233  2005/09/06
• 8-15 アーバスキュラー菌根菌による有機態リン酸の利用(8.共生,日本土壌肥料学会 2005年度大会講演要旨集)

  俵谷 圭太郎, 白井 幸輔, 三橋 渉, 江澤 辰広, 我妻 忠雄  日本土壌肥料学会講演要旨集  (51)  53  -53  2005/09/06
• 8-18 アーバスキュラー菌根菌における菌糸内ポリリン酸輸送速度解析法の確立と宿主へのリン酸供給能評価(8.共生,日本土壌肥料学会 2005年度大会講演要旨集)

  江沢 辰広, 森 昭暢, 大友 量, 大崎 満  日本土壌肥料学会講演要旨集  (51)  54  -54  2005/09/06
• アブラナ科植物根こぶ病菌のリボソームRNA遺伝子IGS領域のクローニング : レース判定への利用は可能か?(7. 土壌病害, 2004年度大会講演要旨集)

  丹羽 理恵子, 江沢 辰広  日本土壌肥料学会講演要旨集  (50)  53  -53  2004/09/14
• 根圏環境：機能解明から制御へ.

  西山雅也, 橋床泰之, 江沢辰広, 大崎満, Fusuo Zhang, 齋藤雅典  土肥誌  75-  405  -410  2004  [Not refereed][Not invited]
  
• 8-26 撹乱により生じた酸性硫酸塩土壌へのアーバスキュラー菌根菌の侵入・定着(8.共生)

  野町 美弥, 江沢 辰広  日本土壌肥料学会講演要旨集  (49)  63  -63  2003/08/20
• 8-28 リン酸欠乏処理後のアーバスキュラー菌根菌におけるポリリン酸の急速な合成と蓄積(8.共生)

  江沢 辰広, Cavagnaro Timothy, 大友 量  日本土壌肥料学会講演要旨集  (49)  64  -64  2003/08/20
• IV-2 菌根共生における養分の獲得機構解明(IV 根圏環境 : 機能解明から制御へ)

  江沢 辰広  日本土壌肥料学会講演要旨集  (49)  209  -209  2003/08/20
• Plant-Microbe Symbosis(Division 3 : Soil Biology)

  Yasuda T., Ezawa T.  Japanese journal of the science and plant nutrition  73-  635  -640  2002/10
• Phosphate Acquisition and Metabolism in Arbuscular Mycorrhizal Association(The Progress Awards)

  Ezawa T.  Journal of the science of soil and manure, Japan  73-  (3)  255  -256  2002/06/05
• 奨-2 アーバスキュラー菌根共生系に特異的なリン酸獲得・代謝メカニズム(日本土壌肥料学会奨励賞)

  江沢 辰広  日本土壌肥料学会講演要旨集  (48)  190  -190  2002/03/25
• 8-9 菌根形成により発現誘導される宿主の分泌型酸性ホスファターゼ遺伝子(8.共生)

  江沢 辰広, 澤木 弘道, 斎藤 雅典  日本土壌肥料学会講演要旨集  (48)  39  -39  2002/03/25
• 8-1 酸性硫酸塩土壌から分離したパイオニア植物共生微生物の同定(8.共生)

  野町 美弥, 牧 孝憲, 江沢 辰広, 吉田 重方  日本土壌肥料学会講演要旨集  (48)  37  -37  2002/03/25
• 22-2 酸性硫酸塩土壌におけるパイオニア植物および共生微生物の探索と利用(22.緑化技術)

  牧 孝憲, 朝倉 嘉子, 江澤 辰広, 和田 富吉, 吉田 重方  日本土壌肥料学会講演要旨集  (47)  194  -194  2001/03/25

Association Memberships

• 植物微生物研究会   菌根研究会   日本土壌肥料学会   International Mycorrhiza Society   

Research Projects

• Microbial networks as a basis of survival strategy in nutrient-deficient enviornment

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2023/04 -2026/03 

  Author : 江澤 辰広, 杉原 創
• 植物の土壌リン獲得シンドロームの解明と新たな陸域生態系リン循環モデルの構築

  日本学術振興会：科学研究費助成事業

  Date (from‐to) : 2021/04 -2024/03 

  Author : 北山 兼弘, 江澤 辰広, 向井 真那, 和穎 朗太
• Robustness and modeling of microbial symbiosis in plants: application of field transcriptomics

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2020/04 -2023/03 

  Author : 江澤 辰広

   

  農工大の有機物25年連用圃場において秋まきコムギを栽培し、有機物連用区、化学肥料連用区、および無施肥区から根および地上部、根域土壌を採取した（n = 4, 合計12サンプル）。また、海外研究協力者であるスイス農業研究機関Agroscopeのvan der Heijden博士（チューリッヒ大兼任教授）らの持つ現地農家とのネットワークを利用し、有機物連用および慣行栽培圃場のそれぞれ8試験地から採取したコムギ根および地上部を入手した（n = 8, 合計128サンプル）。これら根から精製したmRNAのシーケンスを行い、得られたリードをコムギゲノムへマッピングして各遺伝子の発現量を算出すると共に、菌根菌のリボソームRNAデータベースに対して相同性検索も行い、各サンプルにおける菌根菌の相対バイオマスを算出した。地上部は酸分解後、窒素およびリン含量を測定した。根域土壌は理化学性分析に供した。今年度、得られた発現データに昨年度取得したデータを加え、遺伝子共発現ネットワーク解析を行って22個の遺伝子共発現モジュールを規定した。この中には菌根形成を制御する遺伝子モジュールが含まれており、このモジュールの発現レベルを有機物連用との関係において解析したが、有意な相関は認められなかった。一方、菌根菌バイオマスは、ほとんどの試験地において有機物連用区で高く、地上部の窒素含量と負の相関を示したことから、コムギでは菌根に対して窒素獲得への依存度が高いことが示唆された。
• セスバニア根粒菌の病原性と細胞内感染能：非マメ科植物への感染拡大に向けた基盤研究

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  Date (from‐to) : 2019/04 -2022/03 

  Author : 青野 俊裕, 江澤 辰広, 小川 哲弘, 石綱 史子

   

  セスバニア根粒菌は、マメ科植物セスバニアに根粒・茎粒を形成するが、非マメ科植物 のエンドファイトでもあり、単生窒素固定細菌でもある。我々は、本菌はR-body生産という病原菌的側面を持っており、セスバニアへの細胞内感染後に宿主細胞を殺傷できることを見出している。R-bodyとは、reb遺伝子群にコードされる低分子タンパク質群の巨大ポリマーである。セスバニア根粒菌は、reb遺伝子群と自己転写促進因子をコードするrebオペロンを持っており、通常はrebオペロン外にコードされる転写因子群によってその発現が抑制されている。また、rebオペロンの発現に必須な転写因子もまた、rebオペロン外の遺伝子によってコードされていることが昨年度までに判明した。一方、本菌は非マメ科植物であるシロイヌナズナの全身に、部位によっては細胞内にも感染できることも、我々は見出している。 本菌の病原性と感染性を最大限に制御・利用すれば、広範囲の非マメ科植物に本菌を定着させ、高い窒素固定活性を発揮させることができると我々は考えている。その基盤を築くため、本研究では、R-bodyの生産機構と病原性作用機序の解明と、シロイ ヌナズナへの全身感染・細胞内感染機構の解明を目的としている。 本年度は、rebオペロンの発現制御系の解明を更に深めた。これまで、rebオペロンの発現に影響を及ぼす環境要因として、環境中の2オキソグルタル酸濃度と温度を見出してきた。本年度は、ゲノムワイドな変異株スクリーニングを行うことで、シデロフォア生産関連遺伝子破壊株におけるrebオペロンの発現が異常になることを見出した。シデロフォアは細菌が環境中の鉄を獲得するのに重要な役割を果たすことが知られている。これをヒントに実験を行ったところ、鉄濃度がrebオペロンの発現に影響を及ぼすという新事実を見出すことができた。
• 植物耐酸性研究の新展開：菌根形成による耐酸性獲得の生理・分子機構

  文部科学省：科学研究費補助金(基盤研究(B))

  Date (from‐to) : 2017/04 -2020/03 

  Author : 江澤 辰広
• 共生ネットワークの分子基盤とその応用展開

  科学技術振興機構：ACCEL

  Date (from‐to) : 2014/12 -2019/11 

  Author : 川口正代司

   

  CRESTでは、菌根菌や根粒菌形成に共通なシグナル伝達経路に関わる宿主因子を同定し、植物から菌根菌への共生シグナルがストリゴラクトンであることを解明するなど、菌根共生系および根粒共生系を支える分子基盤の知見を得ました。 ACCELでは、CRESTにより創出された知見とフィールドにおける栽培試験を融和することにより、菌根菌のゲノムを解読し絶対共生の分子基盤を解明するとともに、全国各地のフィールドにおいて菌根菌接種試験を行い、リン肥料節減の効果を評価します。それに基づき、菌根菌利用診断技術を開発することで、世界的な課題となっているリン肥料節減のために最適な菌根菌利用技術の開発を目指します。
• New insight into plant acid tolerance: physiological and molecular mechanisms of acid tolerance through mycorrhizal formation

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2014 -2016 

  Author : Ezawa Tatsuhiro, SAITO Katsuharu, MARUYAMA Hayato, KAWAHARA Ai, KIKUCHI Yusuke, YOKOYAMA Kaede

   

  Arbuscular mycorrhizal fungi associate with more than 80% of land plants, deliver phosphate to the host, and, in return, receive photosynthate from the host. The molecular mechanism underlying the symbiotic phosphate delivery, however, has yet to be elucidated. For the first time, we have established a gene silencing technique in the fungi using plant viral vector (i.e. virus-induced gene silencing) in this study. With this technique, we demonstrated that a fungal aquaporin mediates long-distance phosphate translocation through hyphae, which is driven by water flow created primarily by transpiration. A phosphate exporter responsible for phosphate transfer from the fungal cell to plant cell is also identified and characterized in this study.
• An alternative strategy for adaptation to acidic soil in plants: molecular basis of symbiotic network with microorganisms

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2010 -2012 

  Author : EZAWA Tatsuhiro, AONO Toshihiro, MASTA Chikara, KAWAHARA Ai, KIKUCHI Yusuke, YOKOYAMA Kaede

   

  Soil acidity inhibits plant root growth and thus constrains plant productivity. Acid-tolerant arbuscular mycorrhizal (AM) fungi allow plant survival in acidic soil. The present study investigated the mechanisms underlying the enhancement of plant acid-tolerance by AM fungi. Acid-tolerant AM fungi provide an alternative pathway of phosphate uptake for the damaged roots. Genes involved in phosphate uptake and their expression in response to increased phosphate availability were demonstrated in an acid-tolerant fungus by transcriptome analysis. Four double-stranded RNA viruses were identified in an acid-tolerant fungus, of which a role in acid-tolerance of the host fungus will be investigated in the future.
• Molecular mechanism of phosphate transport in plant-fungal symbiosis

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2007 -2009 

  Author : Tatsuhiro EZAWA, Toshihiro AONO, Kuga YUKARI, Chiharu TANI, Nowaki HIJIKATA, Masatake MURASE

   

  The present study demonstrated that i) polyphosphate is the main storage of phosphorus in arbuscular mycorrhizal fungi, ii) polyphosphate consists of 60-70% of total cellular phosphorus at maximum, and iii) Na^+, K^+, Ca^<2+>, and Mg^<2+> are also accumulated during polyphosphate accumulation to neutralize negative charge of polyphosphate. An efficient method to extract RNA from hyphae has been established for large scale sequencing of mRNA expressed during polyphosphate accumulation in hyphae.
• 核染色による絶対寄生性土壌病害菌の発芽検定法の確立と発芽誘引シグナルの探索

  文部科学省：科学研究費補助金(萌芽研究)

  Date (from‐to) : 2005 -2008 

  Author : 江澤 辰広

   

  絶対寄生性の土壌病害菌であるアブラナ科根こぶ病菌のレース識別は、従来、検定植物への接種試験により行われていた。これを根こぶ病菌のレース識別を分子マーカーを用いて簡便に行う方法を確立するために、大、小サブユニットリボソームRNA遺伝子の塩基配列、IGS領域および本遺伝子中に発見されたイントロンの解析を行った。1.IGS領域の解析:名古屋大学より分離されたNGY03株のIGS領域には14bpのパリンドローム配列の中心に反復配列が挿入されたものが、987-1248nt領域に5反復存在した。これら反復配列は、本菌のグループ分けの指標となる可能性が示唆された。2.イントロンの解析:大、小サブユニットで発見された4つのイントロンの二次構造予測を行ったところ、Group-Iイントロンに特徴的であるstem-loop構造が見つかった。また、系統解析から、S516_NGYイントロンはGroup-Iイントロンのうちのsubgroup IEに、Pbr.S943_NGY、Pbr.S1506_NGYおよびPbr.1094_Hagiはsubgroup IC1に属することが示された。NGY03株を含む世界各地で分離された7種類の根こぶ病菌のPbr.S1506イントロンの塩基配列の比較により、米国産のArkansas(U19881)のものは、P5ドメインの配列の一部が欠損していることがわかった。さらに、NGY03とArkansas株のその領域の二次構造は異なっていることが推定された。萩市(Hagi)および広島市(Hiroshima)から分離された株で見つかったPbr.L1094イントロンは、HagiとHiroshima間でその長さおよび塩基配列が異なっていた。NGY03株のエクソンおよび各イントロンの塩基配列は、クローン間で相同性が高かったのに対し、HagiおよびHiroshima株で見つかったPbr.S1904イントロンではクローン間で相同性が低く、この領域は地理的隔離株の識別に利用できる可能性が示唆された。一方で、Group-Iイントロンに特徴的なモチーフ配列(P,Q,R,S)は、すべての分離株の間で保存性が高かった。
• Confirmation of multiple symbiotic systems of plant-Frankia-mycorrhiza with a higher stress tolerance and its application to the rehabilitation of degraded lands

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2004 -2007 

  Author : SASAKAWA Hideo, KANZAKI Hiroshi, YAMAMOTO Mikihiro, SHIMA Kazuto, EZAWA Tatsuhiro

   

  This research was clone to establish a multiple symbiotic system of actinorhizal plant-Frankia- mychorrhiza with a higher environmental stress tolerance and to confirm it as an effective system for the recovery of the degraded lands. The results obtained were as follows. 1. One strain from the root nodules of Elaeagnus macrophylla and 4 strains from the root nodules of Myrica rubra were isolated and they were identified as Frankia by their morphological characteristics and inoculation test. 2. Frankia Apel strain was isolated from the root nodules of Alnus pendula growing in acid soil. The growth pH range of the strain was between 6.0 and 8.0, and the value was not different from those of Frankia which were isolated from the root nodules of actinorhizal plants growing in neutral pH. 3. Host range of each Frankia strain obtained by inoculation test and the result of phylogenic analysis with 16S rDNA sequence of each strain were well consistent. 4. Frankia strains reserved in the lab could be well discriminated by RFLP analysis of nifD-KIGS region and this method was effective for the determination of Frankia strain in the nodules of actinorhizal plants growing under natural conditions. 5. Pisolithus tinctorius or Cenococcum geophilum which had been isolated and reserved were inoculated with Frankia to 4 actinorhizal plants, but no mycorrhizal infection was observed. 6. One mycorrhiza-like fungus was isolated from 4 species of pine mycorrhizal mushrooms, respectively, and also one mycorrhiza-like fungus was isolated from mycorrhizal mushroom of Alnus sieboldiana. PCR-RFLP analyses strongly suggested that these fungi could be mycorrhizal fungi which infect on both pine and Alnus species. These results gave us a prospect for the establishment of tripartite symbiotic system on actinorhizal plants which is effective for the recovery of the degraded lands
• Long-distance translocation of phosphate in arbuscular mycorrhizal association

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))

  Date (from‐to) : 2005 -2006 

  Author : Tatsuhiro EZAWA, Yukari KUGA

   

  Polyphosphate synthetic activity and phosphatase specific to mycorrhizal formation were investigated to clarify the mechanism of phosphorus (P) acquisition in arbuscular mycorrhizal association.1. Polyphosphate synthesis in arbuscular mycorrhizal fungiPolyphosphate (polyP) is a linear polymer of phosphate linked by high-energy bonds and plays significant roles in P-delivery in the associations. Extraradical hyphae were collected and subjected to cell fractionation to isolated organelles involved in polyP synthesis. PolyP synthetic activity was detected and characterized for the first time in fungi. PolyP was synthesized using ATP as substrate, but the synthesis was not supported by proton-gradients created by H^+-ATPase. The activity was induced in the P-deficient hyphae by phosphate application.2. Up-regulation of secreted acid phosphatase gene in host plantThe mycorrhiza-responsive phosphatase was detected by electrophoresis, purified by column chromatography and characterized as acid phosphatase that was secreted into rhizosphere. A cDNA fragment of the phosphatase gene (TpPAPI) was amplified by degenerate primers designed based on the N-terminal amino acid sequence. The full-length cDNA was obtained by the RACE technique. TpPAPI was of host origin, and the cDNA was 1,843 bp long with a predicted open reading frame of polypeptide of 466 amino acids. Phylogenetic analysis revealed that the gene fell into the cluster of plant high molecular weight purple acid phosphatase. Expression analysis of the TpPAPI showed that the levels of transcripts increased 8-fold by mycorrhizal colonization. Western blot analysis revealed that the 57 kDa protein corresponding to the mycorrhiza-responsive phosphatase increased by mycorrhizal colonization. The present study proposes a new strategy for acquisition of P in arbuscular mycorrhizal associations in which the fungal partner activates a part of the low-P adaptation system of the plant partner, phosphatase secretion, and improves the overall efficiency of P uptake.
• Breeding strategy for P-efficient plants

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2003 -2006 

  Author : KOYAMA Hiroyuki, EZAWA Tatsuhiro, KIMURA Kazuhiko

   

  Development of P-efficient plants, which can grow better than regular crop plants by enhanced ability of P-uptake from soil, would be important targets in plant breeding. Enhancement of organic acid excretion from the root, which seemed to be involved in P-deficiency responsive mechanisms, is one promising approach to realize this breeding target. Furthermore, it should be considered plant-microbial interaction and plant-soil interaction to develop "real P-efficient plants" showing superior growth performance in natural environment because these interactions should affect efficiency of P solublization by excreted OA. From these concepts, we completed research and obtained following findings. 1) OA excretion mechanism in Carrot IPG cell line and white lupin The IPG (Insoluble phosphate grower) can release large amounts of citrate than parental cell line. Using RNAi techniques, we showed proton pumping is involved in this capacity. Also, we found that altered OA metabolism play a key role in OA excretion in white lupin. 2) Genomics approach for malate transporter in Arabidopsis We identified QTL controlling AL tolerance in Arabidopsis and identified a key gene in this locus, namely AtALMT1 encoding a Al-responsive malate transporter in Arabidopsis. Using micro-array and genetic approaches, we found correlation between expression level of the gene and malate release capacity. We also have characterized the AtALMTI expression and regulation and found that involvement of a reversible phosphorylation in regulating these mechanisms. 3) Plant-Microbe and Soil interactions We found that OA release should be balanced by micoryiza system in terms of carbon economy because OA release and micoryiza system additively contribute on P-uptake in wheat. In addition, we established sensitive and high throughput system for quantifying system for meal contents in Arabidopsis using ICP-MASS. Using this system, we identified improved uptake of nutrients by transgenic plants.
• Studies on the establishment and element supply ability of arbusculer mycorrhizal symbiosis using the hyper-mycorrhizal soybean mutant

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2004 -2005 

  Author : SAKAMOTO Kazunori, TAWARAYA Keitaro, EZAWA Tatsuhiro, ISOI Toshiyuki, SUZUKI Hiroyuki

   

  We studied the establishment and element supply ability of arbusculer mycorrhizal symbiosis using the hyper-mycorrhizal soybean mutant. The results obtained were summarized as follows : 1. Hyper-mycorrhizal soybean mutant, En6500, showed higher arbuscular abundance compared with the wild type Enrei. We elucidated that soybean shoot is responsible for the negative regulation of arbuscule formation. 2. We found that the root-derived material of soybean root is not involved in the growth of external hyphae of arbuscular mycorrhizal fungi. 3. Hyper-nodulating soybean genotype Sakukei 4, as well as En6500, showed higher arbuscular abundance compared with the wild type Enrei. 4. We found the poly-phosphate accumulating organella involved in the transport of phosphate in the external hyphae of arbuscular mycorrhizal fungi. 5. We clarified that the uptake of some microelements are related to the degree of arbuscule formation in the root.
• Mechanism of phosphate accumulation and translocation in arbuscdar mycorrhizal assodation and its application to environmental restoration

  Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(C))

  Date (from‐to) : 2003 -2004 

  Author : Tatsuhiro EZAWA

   

  I.Analysis of the rate of polyphosphate translocation through hyphaeWe have established a method to quantify polyphosphate (polyP) in hyphae of arbuscular mycorrhizal fungi using the polyphosphate kinase/luciferase system. The rate of polyP translocation was compared between Glomus sp.HR1, Archaeospora leptoticha OK-15 and Glomus etunicatum in symbiosis with Lotus japonicus under acidic (pH 4.3) and neutral (pH 7.0) conditions. Glomus sp. HR1 and A.leptoticha OK-15 which were isolated from acidic soil promoted the growth of the host at pH 4.3 and 7.0. In contrast, G.etunicatum, an isolate from neutral soil, colonized and promoted the growth of the host only at pH 7.0 but not colonized at pH 4.3. The rate of polyP translocation in Glomus sp. HR1 and A.leptoticha OK-15 was significantly different between the isolates, 1.11 and 0.48 min h^<-1>, respectively, the influence of soil pH on the rate was not observed.II.Ecology of arbuscular mycorrhizal fungi in acid sulfate soilWe succeeded to isolate arbuscular mycorrhizal fungi from the rhizosphere of pioneer plants in acid sulfate soils in Hazu-cho, Aichi and Rankoshi-cho, Hokkaido. It was found that Glomus sp. HR1 from Aichi and Glomus sp. RF1 from Hokkaido belonged to the same cluster based on a phylogenetic analysis of 18S rRNA gene, this suggested that these fungi adapted to acidic environment. The involvement of fungal diversity in the growth of pioneer plants was investigated by a pot experiment using rhizosphere soil collected from several pioneer plants. The growth of the plants was greater in the soil showing higher fungal diversity, indicating the significance of fungal diversity in the survival and growth of the pioneer plants.
• 植物-菌根菌共生系に特異的なリン酸獲得・濃縮・輸送メカニズムの解明

  文部科学省：科学研究費補助金(奨励研究(A), 若手研究(B))

  Date (from‐to) : 2001 -2002 

  Author : 江澤 辰広

   

  アーバスキュラー菌根共生系におけるリン酸の獲得・濃縮・輸送のメカニズムを解明する目的で、共生特異的に宿主の根から分泌される酸性ホスファターゼの全長cDNAの塩基配列決定および遺伝子発現解析を行うと共に、菌根菌のプロトプラスト作製のための予備検討を行った。1.共生特異的酸性ホスファターゼの全長cDNA塩基配列の決定および遺伝子発現解析精製された共生特異的酸性ホスファターゼのN末端アミノ酸配列15残基を基にPCRプライマーを設計し、3'/5'RACE法によりcDNA(TPAP1)の全長塩基配列を決定した。TPAP1は,1,8kbpからなり,N末端部分に34残基のシグナルペプチドを含む466残基のアミノ酸をコードしていた.また,TPAP1の5'端非翻訳領域は,同遺伝子の3'端非翻訳領域と相補的な40塩基ほどの配列を有していた.RT-PCRとそれに続くサザンハイブリダイゼーションにより,菌根形成によるTPAP1mRNA発現量の変化を調べた.TPAP1の発現量は菌根形成により3〜10倍に増加した.また、TPAP1のC末端に対する抗体を用いたWestern blottingにより、TPAP1の定量を行ったところ、酵素活性の上昇と共にタンパク量も増加していたことから、本酵素の活性は遺伝子発現のレベルで制御されていることが示唆された。2.菌根菌プロトプラスト作製のための予備検討パッチクランプ法による菌根菌細胞膜上のリン酸輸送体の活性検出を目的として、アデレード大(オーストラリア)S. Tyerman教授のもとで菌根菌のプロトプラスト作製を試みた.高浸透液中で根細胞を酵素消化後、徐々に溶液の浸透圧を低下させると、菌糸の切断面からプロトプラストが突出してくる現象を認めた。今後はこの手法を用いて、Tyerman教授との共同研究でパッチクランプを行う予定である。
• Mutuallstic symbiosis between nodulating plants and two district categories of microorganisms.

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 1996 -1998 

  Author : YOSHIDA Shigekata, EZAWA Tatsuhiro, TASHIRO Toru

   

  Nitrogen fixing bacteria in concert with legumes fix atomospheric nitrogen and vescular-arbuscular mycorrhiza (AM) assist legumes, as well as many other plants in the absorption of phosphorus and other inorganic nutrients from soil. Nodulating soybean plants cam be infected by bradyrhizobium and mycorrhisa, while non-nodulating soybeam plants can be only associated with mycorrhiza. The purpose of this study ii (1) to clear the interaction effect of two categories of microorganisms (bradyrhizobium, vascular-arbuacular mycorrhiza) and (2) to find out the optimum soil conditions for soybean plants grown under mutualistic symbiosis. 1. Dually-infected nodulating soybean plants showed the remarkable increase in plants growth marketable pod yield, nodule formation and nitrogen fixing activity over the single infected non-nodulating soybean plants. 2. The growth, nodulation and nitrogen fixing activity of nodulating soybean plants decreased by the restriction of rhizosphere although nodule weight and nitrogen fixing activity per unit weight of root adversely increased. 3. Mycorrhizal infection percentages on the nodulating soybean plants was adversely correlated with available phosphorus content in soiland also depended on the other cultivation managements such as cropping systems. The mycorrhizal infection on marigold roots was the highest at the cultivation of sweetcorn as the preceding plants. 4. Mycorrhizal infection and plant growth of marigold grown as indicator plant were enhanced by the application of some soil amendants such as husk-charcoal. Howver, the growth, plant total nitrogen and plant totalphosphorus of dually infected nodulating soybean plants increased by the application of husk-charcoal although mycorrhizal infection did not increase. These results implies that the effect of husk-charcoal application on dually infected nodulating soybean plants mainly depend on the supply of fixed nitrogen from modules.
• Arbuscular菌根菌共糸における共生特異的リン酸代謝に関する研究

  文部科学省：科学研究費補助金(奨励研究(A))

  Date (from‐to) : 1996 -1996 

  Author : 江澤 辰広

   

  Arbuscular菌根共生系における菌根菌から宿主植物へのリン酸移行のメカニズムを解明する目的で、共生特異的に発現する酸性およびアルカリ性ホスファターゼの性質について検討を行った。1.共生特異的酸性ホスファターゼ(infection-specific acid phosphatase ; ISPase)(1)N末端アミノ酸配列の決定:精製された酵素標品よりN末端アミノ酸配列15残基を決定した。さらに、この配列を基にタンパク質データベース上で相同なものを検討したところ、他の植物の酸性ホスファターゼのN末端配列と相同性が高かった。このことはISPaseが宿主植物由来であることを強く示唆していた。(2)活性発現部位の推定:菌根における酸性ホスファターゼ活性部位を組織化学的方法により調べたところ、主に菌根菌組織の周辺部や植物根の細胞壁部分で高い活性が認められたことから、ISPaseは分泌型の酵素であることが予想された。また、ISPaseが根の分泌液中から検出されたことも仮説を支持していた。2.アルカリ性ホスファターゼ(1)粗酵素液調製法:共生状態の菌根菌組織に特異的に発現するアルカリ性ホスファターゼの機能を推定するために、宿主根をセルラーゼなどで消化後、菌根菌組織を顕微鏡下で摘出し、そこから得られる可溶性および不溶性画分におけるホスファターゼ活性を測定する方法を確立した。(2)特異的阻害剤と基質特異性:本酵素の活性はベリリウムにより特異的に阻害された。また、このことを利用して基質特異性や動力学定数などを求めたところ、糖リン酸に対する基質特異性が高いことが明らかになった。

Industrial Property Rights

• 特願2020-194968:宿主植物と微生物との共生程度を推定する方法、および予測モデ ルを作成する方法  2020年/11/25

  吉村愛, 廣富大, 江澤辰広, 杉村悠作, 丸山隼人  住友化学株式会社, 国立大学法人北海道大学
• 特願2019-080349:アーバスキュラー菌根菌の培養用培地及び培養方法  2019年/04/19

  川口 正代司, 田中 幸子, 矢野 幸司, 秋山 康紀, 齋藤 勝晴, 江澤 辰広
• 特願2010-125861:法面緑化工法  

  江沢辰広, 大崎満, 宮川祥江, 田中淳, 堀江直樹, 伴資英  

  特開2011-250729