基本情報

所属

• 理学研究院　生物科学部門　形態機能学分野

職名

• 教授

学位

• 理学博士

J-Global ID

• 200901080863488046

研究キーワード

• エピジェネティックス   シロイヌナズナ   転写制御   rRNA   non-coding RNA   micro RNA   花茎伸長   PTGS   トランス因子   antisense RNA   分子系統   核分裂   

研究分野

• ライフサイエンス / 分子生物学
• ライフサイエンス / 形態、構造

職歴

• 2008年 - 現在 北海道大学 大学院・理学研究院 教授

所属学協会

• 日本遺伝学会   日本植物生理学会   日本植物学会   

研究活動情報

論文

• Inducible Transposition of a Heat-Activated Retrotransposon in Tissue Culture

  Yukari Masuta, Kosuke Nozawa, Hiroki Takagi, Hiroki Yaegashi, Keisuke Tanaka, Tasuku Ito, Hideyuki Saito, Hisato Kobayashi, Wataru Matsunaga, Seiji Masuda, Atsushi Kato, Hidetaka Ito

  PLANT AND CELL PHYSIOLOGY 58 2 375 - 384 2017年02月 [査読有り][通常論文]
   

  A transposition of a heat-activated retrotransposon named ONSEN required compromise of a small RNA-mediated epigenetic regulation that includes RNA-directed DNA methylation (RdDM) machinery after heat treatment. In the current study, we analyzed the transcriptional and transpositional activation of ONSEN to better understand the underlying molecular mechanism involved in the maintenance and/or induction of transposon activation in plant tissue culture. We found the transposition of heat-primed ONSEN during tissue culture independently of RdDM mutation. The heat activation of ONSEN transcripts was not significantly up-regulated in tissue culture compared with that in heat-stressed seedlings, indicating that the transposition of ONSEN was regulated independently of the transcript level. RdDM-related genes were up-regulated by heat stress in both tissue culture and seedlings. The level of DNA methylation of ONSEN did not show any change in tissue culture, and the amount of ONSEN-derived small RNAs was not affected by heat stress. The results indicated that the transposition of ONSEN was regulated by an alternative mechanism in addition to the RdDM-mediated epigenetic regulation in tissue culture. We applied the tissue culture-induced transposition of ONSEN to Japanese radish, an important breeding species of the family Brassicaceae. Several new insertions were detected in a regenerated plant derived from heat-stressed tissues and its self-fertilized progeny, revealing the possibility of molecular breeding without genetic modification.
• A Stress-Activated Transposon in Arabidopsis Induces Transgenerational Abscisic Acid Insensitivity

  Hidetaka Ito, Jong-Myong Kim, Wataru Matsunaga, Hidetoshi Saze, Akihiro Matsui, Takaho A. Endo, Yoshiko Harukawa, Hiroki Takagi, Hiroki Yaegashi, Yukari Masuta, Seiji Masuda, Junko Ishida, Maho Tanaka, Satoshi Takahashi, Taeko Morosawa, Tetsuro Toyoda, Tetsuji Kakutani, Atsushi Kato, Motoaki Seki

  SCIENTIFIC REPORTS 6 23181  2016年03月 [査読有り][通常論文]
   

  Transposable elements (TEs), or transposons, play an important role in adaptation. TE insertion can affect host gene function and provides a mechanism for rapid increases in genetic diversity, particularly because many TEs respond to environmental stress. In the current study, we show that the transposition of a heat-activated retrotransposon, ONSEN, generated a mutation in an abscisic acid (ABA) responsive gene, resulting in an ABA-insensitive phenotype in Arabidopsis, suggesting stress tolerance. Our results provide direct evidence that a transposon activated by environmental stress could alter the genome in a potentially positive manner. Furthermore, the ABA-insensitive phenotype was inherited when the transcription was disrupted by an ONSEN insertion, whereas ABA sensitivity was recovered when the effects of ONSEN were masked by IBM2. These results suggest that epigenetic mechanisms in host plants typically buffered the effect of a new insertion, but could selectively "turn on" TEs when stressed.
• AtRBP1, which encodes an RNA-binding protein containing RNA-recognition motifs, regulates root growth in Arabidopsis thaliana

  Takuhiro Shida, Ai Fukuda, Tamao Saito, Hidetaka Ito, Atsushi Kato

  PLANT PHYSIOLOGY AND BIOCHEMISTRY 92 62 - 70 2015年07月 [査読有り][通常論文]
   

  AtRBP1 is an RNA-binding protein containing RNA-recognition motifs in Arabidopsis thaliana, homologues of which are not observed in metazoa. Transgenic plants expressing artificial microRNAs for repressing AtRBP1 expression displayed a stunted primary root phenotype during germination. Transgenic plants overexpressing AtRBP1 also displayed the same phenotype. Tight regulation of the AtRBP1 transcript may be required for normal root growth. An in vitro binding assay showed that AtRBP1 preferentially binds to sequences containing UUAGG, GUAGG and/or UUAGU. In vivo selection of RNAs bound to AtRBP1 suggests that transcripts of At3g06780, At4g15910, At5g11760 and At5g07350 are target RNAs of AtRBP1. (C) 2015 Elsevier Masson SAS. All rights reserved.
• Role of the ACL2 locus in flower stalk elongation in Arabidopsis thaliana

  Hiroaki Kato, Yoshibumi Komeda, Tamao Saito, Hidetaka Ito, Atsushi Kato

  GENES & GENETIC SYSTEMS 90 3 163 - 174 2015年06月 [査読有り][通常論文]
   

  The acaulis2 (acl2) mutant of Arabidopsis thaliana shows a defect in flower stalk elongation. We identified the mutation point of acl2 by map-based cloning. The ACL2 locus is located within an approximately 320-kb region at around 100 map units on chromosome 1. One nucleotide substitution was detected in this region in the acl2 mutant, but no significant open reading frames were found around this mutation point. When wild-type DNA fragments containing the mutation point were introduced into acl2 mutant plants, some transgenic plants partially or almost completely recovered from the defect in flower stalk elongation. 3'-RACE experiments showed that bidirectional transcripts containing the acl2 mutation point were expressed, and the Plant MPSS database revealed that several small RNAs were produced from this region. Microarray analysis showed that transcription of many genes is activated in flower stalks of acl2 mutant plants. Overexpression of some of these genes caused a dwarf phenotype in wild-type plants. These results suggest the following novel mechanism for control of the elongation of flower stalks. Bidirectional non-coding RNAs are transcribed from the ACL2 locus, and small RNAs are generated from them in flower stalks. These small RNAs repress the transcription of a set of genes whose expression represses flower stalk elongation, and flower stalks are therefore fully elongated.
• A small RNA mediated regulation of a stress-activated retrotransposon and the tissue specific transposition during the reproductive period in Arabidopsis

  Wataru Matsunaga, Naohiko Ohama, Noriaki Tanabe, Yukari Masuta, Seiji Masuda, Namiki Mitani, Kazuko Yamaguchi-Shinozaki, Jian F. Ma, Atsushi Kato, Hidetaka Ito

  FRONTIERS IN PLANT SCIENCE 6 48  2015年02月 [査読有り][通常論文]
   

  Transposable elements (TEs) are key elements that facilitate genome evolution of the host organism. A number of studies have assessed the functions of TEs, which change gene expression in the host genome. Activation of TEs is controlled by epigenetic modifications such as DNA methylation and histone modifications. Several recent studies have reported that TEs can also be activated by biotic or abiotic stress in some plants. We focused on a Ty1/copia retrotransposon, ONSEN, that is activated by heat stress (HS) in Arabidopsis. We found that transcriptional activation of ONSEN was regulated by a small interfering RNA (siRNA)-related pathway, and the activation could also be induced by oxidative stress. Mutants deficient in siRNA biogenesis that were exposed to HS at the initial stages of vegetative growth showed transgenerational transposition. The transposition was also detected in the progeny, which originated from tissue that had differentiated after exposure to the HS. The results indicated that in some undifferentiated cells, transpositional activity could be maintained quite long after exposure to the HS.
• Genomic localization of AtRE1 and AtRE2, copia-type retrotransposons, in natural variants of Arabidopsis thaliana

  Mari Yamada, Yumi Yamagishi, Masashi Akaoka, Hidetaka Ito, Atsushi Kato

  MOLECULAR GENETICS AND GENOMICS 289 5 821 - 835 2014年10月 [査読有り][通常論文]
   

  Retrotransposons are ubiquitous components of plant genomes. They affect genome organization, and can also affect the expression patterns of neighboring genes. Retrotransposons are therefore important elements for changing genomic information. To understand the evolution of the Arabidopsis genome, we examined the distribution of certain retrotransposons, AtRE1s and AtRE2s, in the genomes of 12 natural variants (accessions) of Arabidopsis thaliana. AtRE1 and AtRE2 are copia-type retrotransposons that are potentially active. Their copy numbers are low, and they are absent from the genomes of some accessions. We detected four loci with AtRE1s inserted in six accessions, and one locus with an insertion of a solo-LTR-like sequence derived from AtRE1 in two accessions. Seven loci with AtRE2s inserted were detected on eight accessions. These loci were distributed in euchromatic regions of chromosomes 1, 2, 3, and 4. The AtRE1 and AtRE2 sequences at some loci identified in this study have not been recorded in the database of the 1001 Genome project. The sequences of AtRE1s and those of AtRE2s in different accessions and at different loci were highly conserved. There was a complete or almost complete conservation of sequences of both long terminal repeats in each AtRE1 and in each AtRE2. These results suggest that AtRE1 and AtRE2 appeared quite recently in the Arabidopsis genome. Furthermore, sequence comparisons of AtRE1 and AtRE2 loci among accessions revealed the possibility that large deletions containing entire sequences of AtRE1 and AtRE2 have occurred in some accessions.
• Overexpression of the TIR-X gene results in a dwarf phenotype and activation of defense-related gene expression in Arabidopsis thaliana

  Hiroaki Kato, Tamao Saito, Hidetaka Ito, Yoshibumi Komeda, Atsushi Kato

  JOURNAL OF PLANT PHYSIOLOGY 171 6 382 - 388 2014年03月 [査読有り][通常論文]
   

  The Arabidopsis genome encodes various proteins with a Toll/interleukin-1 receptor (TIR) domain. Many of these proteins also contain nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains and function as resistance (R) proteins. However, the protein encoded by At2g32140 (a TIR-X gene) contains a TIR domain but lacks NBS and LRR domains. We found that transgenic plants overexpressing At2g32140 displayed a dwarf phenotype and showed increased expression of defense-related genes. In general, the growth defect caused by activation of defense responses is suppressed under high-temperature conditions. However, transgenic plants overexpressing At2g32140 displayed a much stronger dwarf phenotype at 28 degrees C than at 22 degrees C. This dwarf phenotype was suppressed under the combination with known salicylic-acid pathway mutants. These findings suggest that At2g32140 encodes a protein involved in the plant defense response. (C) 2013 Elsevier GmbH. All rights reserved.
• Identification of Des-methyl-DIF-1 Methyltransferase in Dictyostelium purpureum

  Kazunori A. Motohashi, Naoki Morita, Atsushi Kato, Tamao Saito

  BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY 76 9 1672 - 1676 2012年09月 [査読有り][通常論文]
   

  The signalling molecule 1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl) hexan-1-one (DIF-1) is required for differentiation and pattern formation in Dictyostelium discoideum development. DIF-1 is synthesized by three enzymes, a hybrid polyketide synthase, a flavin-dependent halogenase, and a des-methyl-DIF-1 methyltransferase. The genome data on the related species D. purpureum are now public. Using this genome information, des-methyl-DIF-1 methyltransferase of D. purpureum was identified, and was named Dp dmtA. Overexpression of Dp dmtA complemented the defects in basal disc formation and lower cup formation in a dmtA knock-out.,mutant of D. discoideum. This indicates that Dp dmtA has the same function as D. discoideum dmtA and compensates for loss of the dmtA gene in the D. discoideum dmtA mutant. The materials released in the medium by D. purpureum contained stalk-inducing activity with the same retention time as that of DIF-1 in HPLC fractionation. This indicates that the stalk-inducing signal of DIF-1 and des-methyl-DIF-1 methyltransferase are conserved in D. purpureum.
• The effects of heat induction and the siRNA biogenesis pathway on the transgenerational transposition of ONSEN, a copia-like retrotransposon in Arabidopsis thaliana

  Wataru Matsunaga, Akie Kobayashi, Atsushi Kato, Hidetaka Ito

  PLANT AND CELL PHYSIOLOGY 53 5 824 - 833 2012年05月 [査読有り][通常論文]
   

  Environmental stress influences genetic and epigenetic regulation in plant genomes. We previously reported that heat stress activated a copia-like retrotransposon named ONSEN. To investigate the heat sensitivity and transgenerational activation of ONSEN, we analyzed the stress response by temperature shift and multiple heat stress treatments. ONSEN was activated at 37 degrees C, and the newly inserted ONSEN was transcriptionally active and mobile to the next generation subjected to heat stress, indicating that the regulation of ONSEN is independent of positional effects on the chromosome. Reciprocal crosses with activated ONSEN revealed that the transgenerational transposition was inherited from both sexes, indicating that the transposition is suppressed independently of gametophytic regulation. We showed previously that ONSEN was transposed in mutants deficient in small interfering RNA (siRNA) biogenesis, including nrpd2 and rdr2, but not dcl3. To define the functional redundancy of Dicer-like (DCL) proteins in Arabidopsis, we analyzed ONSEN activation in mutants deficient in DCL proteins, including dcl2, dcl3 and dcl4. ONSEN was nearly immobile in a single Dicer mutant; however, some transgenerational transpositions were observed in dcl2/dcl3/dcl4 triple mutants subjected to heat stress. This indicated that the Dicer family is redundant for ONSEN transposition. To examine the activation of ONSEN in undifferentiated cells, ONSEN transcripts and synthesized DNA were analyzed in heat-stressed callus tissue. In contrast to vegetative tissue, high accumulation of the transcripts and amplified DNA copies of ONSEN were detected in callus. This result indicated that ONSEN activation is controlled by cell-specific regulatory mechanisms.
• Overexpression of the Activated Disease Resistance 1-like1 (ADR1-L1) Gene Results in a Dwarf Phenotype and Activation of Defense-Related Gene Expression in Arabidopsis thaliana

  Hiroaki Kato, Takuhiro Shida, Yoshibumi Komeda, Tamao Saito, Atsushi Kato

  JOURNAL OF PLANT BIOLOGY 54 3 172 - 179 2011年06月 [査読無し][通常論文]
   

  The protein encoded by the activated disease resistance 1-like1 (ADR1-L1) gene (locus name, At4g33300) belongs to the activated disease resistance 1 (ADR1) family of coiled-coil nucleotide-binding site leucine-rich repeat-type disease resistance proteins. This family contains four proteins and they have specific features in their amino acid sequences. It has been reported that ADR1 protein belongs to the ADR1 family, which is related to not only defense response but also drought tolerance. We found that transgenic plants overexpressing the ADR1-L1 gene showed a dwarf phenotype and morphological change in leaves. The expression levels of defense-related genes and the resistance to Pseudomonas syringae pv. tomato DC3000 were increased in transgenic plants. However, enhancement of drought tolerance and activation of abiotic response genes were not observed. When the growth temperature was changed from 22A degrees C to 28A degrees C, the expression of defense-related genes and the enhancement of resistance to a bacterial pathogen were suppressed and the dwarf phenotype and morphological change of leaves recovered.
• Protein Kinase B Gene Homologue pkbR1 Performs One of Its Roles at First Finger Stage of Dictyostelium

  Hiroshi Ochiai, Kosuke Takeda, Masashi Fukuzawa, Atsushi Kato, Shigeharu Takiya, Tetsuo Ohmachi

  EUKARYOTIC CELL 10 4 512 - 520 2011年04月 [査読有り][通常論文]
   

  Dictyostelium discoideum has protein kinases AKT/PKBA and PKBR1 that belong to the AGC family of kinases. The protein kinase B-related kinase (PKBR1) has been studied with emphasis on its role in chemotaxis, but its roles in late development remained obscure. The pkbR1 null mutant stays in the first finger stage for about 16 h or longer. Only a few aggregates continue to the migrating slug stage; however, the slugs immediately go back probably to the previous first finger stage and stay there for approximately 37 h. Finally, the mutant fingers diversify into various multicellular bodies. The expression of the pkbR1 finger protein probably is required for development to the slug stage and to express ecmB, which is first observed in migrating slugs. The mutant also showed no ST-lacZ expression, which is of the earliest step in differentiation to one of the stalk cell subtypes. The pkbR1 null mutant forms a small number of aberrant fruiting bodies, but in the presence of 10% of wild-type amoebae the mutant preferentially forms viable spores, driving the wild type to form nonviable stalk cells. These results suggest that the mutant has defects in a system that changes the physiological dynamics in the prestalk cell region of a finger. We suggest that the arrest of its development is due to the loss of the second wave of expression of a protein kinase A catalytic subunit gene (pkaC) only in the prestalk region of the pkbR1 null mutant.
• Research note: Analysis of expressed sequence tags from the chrysophycean alga Ochromonas danica (Heterokontophyta)

  Makoto Terauchi, Atsushi Kato, Chikako Nagasato, Taizo Motomura

  PHYCOLOGICAL RESEARCH 58 3 217 - 221 2010年07月 [査読無し][通常論文]
   

  P>A cDNA library was constructed from the chrysophycean alga, Ochromonas danica E. G. Pringsheim. 5'-end sequencing of about 600 cDNA clones yielded 476 authentic expressed sequence tags (EST) of which 275 showed significant matches (E-value < 10-4) to sequences in a public database. The annotation of these ESTs was carried out to assess subcellular localization of the putative proteins using several internet-accessible prediction programs for subcellular localization. These analyses revealed that putative plastid proteins in Ochromonas possess N-terminal bipartite presequences with a conserved phenylalanine at the N-terminus of the predicted transit peptide-like domains, similar to other 'red-lineage' secondary symbiotic organisms. The examination of sequences of 3'-UTR revealed that, similarly to chlorophyte algae, UGUAA may represent a putative polyadenylation signal in O. danica.
• Overexpression of the NAC transcription factor family gene ANAC036 results in a dwarf phenotype in Arabidopsis thaliana

  Hiroaki Kato, Taizo Motomura, Yoshibumi Komeda, Tamao Saito, Atsushi Kato

  JOURNAL OF PLANT PHYSIOLOGY 167 7 571 - 577 2010年 [査読有り][通常論文]
   

  NAC proteins comprise one of the largest families of transcription factors in the plant genome. They are known to be involved in various aspects of plant development, but the functions of most of them have not yet been determined. ANAC036, a member of the Arabidopsis NAC transcription factor family, contains unique sequences that are conserved among various NAC proteins found in other plant species. Expression analysis of the ANAC036 gene indicated that this gene was strongly expressed in leaves. Transgenic plants overexpressing the ANAC036 gene showed a semidwarf phenotype. The lengths of leaf blades, petioles and stems of these plants were smaller than those in wild-type plants. Microscopy revealed that cell sizes in leaves and stems of these plants were smaller than those in wild-type plants. These findings suggested that ANAC036 and its orthologues are involved in the growth of leaf cells. (C) 2009 Elsevier GmbH. All rights reserved.
• Evolutionary Process of the Genomic Sequence Around the 100 Map Unit of Chromosome 1 in Arabidopsis thaliana

  Atsushi Kato, Hiroaki Kato, Takuhiro Shida, Tamao Saito, Yoshibumi Komeda

  JOURNAL OF PLANT BIOLOGY 52 6 616 - 624 2009年12月 [査読無し][通常論文]
   

  Comparative analysis of nucleotide sequences of the genomic region located around 100 map unit of chromosome 1 using two accessions, Columbia (Col) and Landsberg erecta (Ler), of Arabidopsis thaliana was performed. High divergence was detected between them, and the length of the Ler sequence was half of corresponding sequence of Col. This divergence occurred by tandem duplication, deletion of large regions, and insertion of unrelated sequences. These events led to the high polymorphism of plant disease resistant genes, which are located in the analyzed region. It is highly probable that two-round duplication occurred, and the insertion sequences are transposable elements. The data suggest that the analyzed region had been evolving until quite recently.
• DIF-1 induces the basal disc of the Dictyostelium fruiting body

  Tamao Saito, Atsushi Kato, Robert R. Kay

  DEVELOPMENTAL BIOLOGY 317 2 444 - 453 2008年05月 [査読有り][通常論文]
   

  The polyketide DIF-1 induces Dictyostelium amoebae to fonn stalk cells in culture. To better define its role in normal development, we examined the phenotype of a mutant blocking the first step of DIF-1 synthesis, which lacks both DIF-1 and its biosynthetic intermediate, dM-DIFI (des-methyl-DIF-1). Slugs of this polyketide synthase mutant (stIB(-)) are long and thin and rapidly break up, leaving an immotile prespore mass. They have similar to 30% fewer prestalk cells than their wild-type parent and lack a subset of anterior-like cells, which later form the outer basal disc. This structure is missing from the fruiting body, which perhaps in consequence initiates culmination along the substratum. The lower cup is rudimentary at best and the spore mass, lacking support, slips down the stalk. The dnitA(-) methyltransferase mutant, blocked in the last step of DIF-1 synthesis, resembles the stlB(-) mutant but has delayed tip formation and fewer prestalk-O cells. This difference may be due to accumulation of dM-DIF-1 in the dintA(-) mutant, since dM-DIF-1 inhibits prestalk-O differentiation. Thus, DIF-1 is required for slug migration and specifies the anterior-like cells forming the basal disc and much of the lower cup; significantly the DIF-1 biosynthetic pathway may supply a second signal - dM-DIF-1. (C) 2008 Elsevier Inc. All rights reserved.
• A tubular mastigoneme-related protein, Ocm1, isolated from the flagellum of a chromophyte alga, Ochromonas danica

  Takahiro Yamagishi, Taizo Motomura, Chikako Nagasato, Atsushi Kato, Hiroshi Kawai

  JOURNAL OF PHYCOLOGY 43 3 519 - 527 2007年06月 [査読無し][通常論文]
   

  The phylogenetic group stramenopiles refers to the systematic groups that possess tripartite tubular hairs (stramenopiles) on their flagella. There have been a number of studies describing the fine structure of these mastigonemes and a few studies isolating the component proteins; however, these proteins and their gene sequences have not yet been identified. In the present study, we identified a mastigoneme protein (Ocm1) of the chrysophycean alga Ochromonas danica Pringsh. (UTEX LB1298). Its corresponding gene, Ocm1, was identified by using degenerate primers that correspond to the partial amino acid sequences of a protein (85 kDa) obtained from a mastigoneme-rich fraction of isolated flagella. The polypeptide encoded by Ocm1 has four cysteine-rich, epithelial growth factor (EGF)-like motifs, potentially involved in protein-protein interactions. It lacks obvious hydrophobic regions characteristic of transmembrane domains, suggesting that this polypeptide is not likely a protein for anchoring the mastigoneme. In addition, a polyclonal antibody against Ocm1 labeled the area where the tubular shafts of the mastigonemes are located, but not the basal portion or the terminal filaments.
• Biosynthesis of Dictyostelium discoideum differentiation-inducing factor by a hybrid type I fatty acid - type III polyketide synthase

  Michael B. Austin, Tamao Saito, Marianne E. Bowman, Stephen Haydock, Atsushi Kato, Bradley S. Moore, Robert R. Kay, Joseph P. Noel

  NATURE CHEMICAL BIOLOGY 2 9 494 - 502 2006年09月 [査読無し][通常論文]
   

  Differentiation-inducing factors (DIFs) are well known to modulate formation of distinct communal cell types from identical Dictyostelium discoideum amoebas, but DIF biosynthesis remains obscure. We report complimentary in vivo and in vitro experiments identifying one of two similar to 3,000-residue D. discoideum proteins, termed ` steely', as responsible for biosynthesis of the DIF acylphloroglucinol scaffold. Steely proteins possess six catalytic domains homologous to metazoan type I fatty acid synthases (FASs) but feature an iterative type III polyketide synthase (PKS) in place of the expected FAS C-terminal thioesterase used to off load fatty acid products. This new domain arrangement likely facilitates covalent transfer of steely N-terminal acyl products directly to the C-terminal type III PKS active sites, which catalyze both iterative polyketide extension and cyclization. The crystal structure of a steely C-terminal domain confirms conservation of the homodimeric type III PKS fold. These findings suggest new bioengineering strategies for expanding the scope of fatty acid and polyketide biosynthesis.
• Identification of new differentiation inducing factors from Dictyostelium discoideum

  Saito T, Taylor GW, Yang JC, Neuhaus D, Stetsenko D, Kato A, Kay RR

  BBA - General Subjects 1706 5 754 - 761 2006年05月 [査読有り][通常論文]
  
• Ultrastructure and immunocytological studies on the rhizoplast in the chrysophcean alga Ochromonus danica

  UEMORI Chihiro, NAGASATO Chikako, KATO Atsushi, MOTOMURA Taizo

  Phyco. Res 54 2 133 - 139 2006年 [査読無し][通常論文]
  
• The antisense promoter of AtRE1, a retrotransposon in Arabidopsis thaliana, is activated in pollens and calluses

  A Kato, M Endo, H Kato, T Saito

  PLANT SCIENCE 168 4 981 - 986 2005年04月 [査読無し][通常論文]
   

  The AtRE1retrotransposon of Arabidopsis thaliana is transcribed in both directions and the amount of sense RNA is much less than that of antisense RNA. The characterization of one cDNA derived from an antisense transcript showed that the antisense RNA is complementary to one half of the open reading frame and 5'-LTR. In order to study the function of this antisense RNA, we characterized the promoter activity for the antisense transcript. Primer extension analysis indicated that the antisense RNA is produced from an internal promoter and indicated the possibility of a plural initiation site of transcription. Promoter analysis using beta-glucuronidase (GUS) gene as a reporter gene showed that the promoter sequence is localized within an approximately 200 bp region upstream from initiation sites of antisense RNA. However, no typical promoter sequences were detected in this region. Histochemical staining of GUS activity indicated that antisense RNAs are transcribed in pollens and actively proliferative regions of calluses. This result suggests that the expression of AtRE1 is repressed by antisense RNA but this mechanism functions in only limited organs. (c) 2004 Elsevier Ireland Ltd. All rights reserved.
• Temperature adaptation in Dictyostelium: role of Delta 5 fatty acid desaturase

  T Saito, A Kato, H Ochiai, N Morita

  MICROBIOLOGY-SGM 151 1 113 - 119 2005年01月 [査読無し][通常論文]
   

  Membrane fluidity is critical for proper membrane function and is regulated in part by the proportion of unsaturated fatty acids present in membrane lipids. The proportion of these lipids in turn varies with temperature and may contribute to temperature adaptation in poikilothermic organisms. The fundamental question posed in this study was whether the unsaturation of fatty acids contributes to the ability to adapt to temperature stress in Dictyostelium. First, fatty acid composition was analysed and it was observed that the relative proportions of dienoic acids changed with temperature. To investigate the role of dienoic fatty acids in temperature adaptation, null mutants were created in the two known Delta5 fatty acid desaturases (FacA and FadB) that are responsible for the production of dienoic fatty acids. The fadB null mutant showed no significant alteration in fatty acid composition or in phenotype. However, the disruption of tadA resulted in a large drop in dienoic fatty acid content from 51(.)2 to 4(.)1% and a possibly compensatory increase in monoenoic fatty acids (40(.)9-92(.)4%). No difference was detected in temperature adaptation with that of wild-type cells during the growth phase. However, surprisingly, mutant cells developed more efficiently than the wild-type at elevated temperatures. These results show that the fatty acid composition of Dictyostelium changes with temperature and suggest that the regulation of dienoic fatty acid synthesis is involved in the development of Dictyostelium at elevated temperatures, but not during the growth phase.
• A xylanase, AtXyn1, is predominantly expressed in vascular bundles, and four putative xylanase genes were identified in the Arabidopsis thaliana genome

  M Suzuki, A Kato, N Nagata, Y Komeda

  PLANT AND CELL PHYSIOLOGY 43 7 759 - 767 2002年07月 [査読有り][通常論文]
   

  The cDNA clone RXF12, which encodes a xylanase (EC 3.2.1.8), was isolated from Arabidopsis thaliana. The C-terminal half of the amino acid sequence of the deduced protein, named AtXyn1, showed similarity with the catalytic domain of barley xylanase X-1. The N-terminal half of AtXyn1 also contained three regions with sequences similar to cellulose-binding domains (CBDs). A xylanase assay revealed that transgenic A. thaliana plants expressing exogenous AtXyn1 fused with enhanced green fluorescent protein (EGFP) possessed approximately twice as much xylanase activity as wild-type plants. Observation by fluorescence microscopy of transgenic A. thaliana plants expressing a fusion protein of AtXyn1 and EGFP suggested that AtXyn1 is a cell wall protein. Analysis of the localization of beta-glucuronidase (GUS) activity in transgenic A thaliana plants containing a chimeric gene with the upstream sequence of the AtXyn1 gene and the GUS gene demonstrated that the AtXyn1 gene is predominantly expressed in vascular bundles, but not in vessel cells. These data suggest that AtXyn1 is involved in the secondary cell wall metabolism of vascular bundle cells. A database search revealed that four putative xylanase genes exist in the A. thaliana genome, besides the AtXyn1 gene. Of these, two also contain several regions with sequences similar to CBDs in their N-terminal regions. Comparison of the amino acid sequences of the five xylanases suggests a possible process for their molecular evolution.
• An RNA-binding protein, AtRBP1, is expressed in actively proliferative regions in Arabidopsis thaliana

  M Suzuki, A Kato, Y Komeda

  PLANT AND CELL PHYSIOLOGY 41 3 282 - 288 2000年03月 [査読無し][通常論文]
   

  A cDNA clone, named XF41, that encodes an RNA-binding protein was isolated from Arabidopsis thaliana. The deduced protein, named AtRBP1, contains two conserved consensus sequence-type RNA-binding domains (CS-RBDs) in the N-terminal half, a putative PY motif (a target of a WW domain) in the center, and uncharacterized C-terminal domain. A binding assay demonstrated that the AtRBP1 can bind to single-stranded nucleic acids in vitro. Analysis of localization of the GUS activity of transgenic Arabidopsis thaliana plants that have the chimeric gene containing the upstream sequence of the AtRBP1 gene and GUS gene demonstrated that the AtRBP1 gene is expressed in meristematic tissues such as the vegetative shoot apex and root tips, developing organs such as floral buds and pistils of young flowers, abscission layers of immature siliques and junctions of pedicels. Considering the specificity of the expression, AtRBP1 may be required in the progress of cell proliferation.

その他活動・業績

• 『植物分子物学』<山田康之>

  朝倉書店 1997年 [査読無し][通常論文]
  

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