研究者データベース

佐々木 隆太(ササキ リユウタ)
創成研究機構 グローバルファシリティセンター
特任助教

基本情報

所属

  • 創成研究機構 グローバルファシリティセンター

職名

  • 特任助教

学位

  • 博士(理学)(筑波大学)

J-Global ID

研究活動情報

論文

  • Ryuta Sasaki, Hisayo Yamane, Tomomi Ooka, Hiroaki Jotatsu, Yuto Kitamura, Takashi Akagi, Ryutaro Tao
    PLANT PHYSIOLOGY 157 1 485 - 497 2011年09月 [査読有り][通常論文]
     
    Bud endodormancy in woody plants plays an important role in their perennial growth cycles. We previously identified a MADS box gene, DORMANCY-ASSOCIATED MADS box6 (PmDAM6), expressed in the endodormant lateral buds of Japanese apricot (Prunus mume), as a candidate for the dormancy-controlling gene. In this study, we demonstrate the growth inhibitory functions of PmDAM6 by overexpressing it in transgenic poplar (Populus tremula x Populus tremuloides). Transgenic poplar plants constitutively expressing PmDAM6 showed growth cessation and terminal bud set under environmental conditions in which control transformants continued shoot tip growth, suggesting the growth inhibitory functions of PmDAM6. In the Japanese apricot genome, we identified six tandemly arrayed PmDAM genes (PmDAM1-PmDAM6) that conserve an amphiphilic repression motif, known to act as a repression domain, at the carboxyl-terminal end, suggesting that they all may act as transcriptional repressors. Seasonal expression analysis and cold treatment in autumn indicated that all PmDAMs were repressed during prolonged cold exposure and maintained at low levels until endodormancy release. Furthermore, PmDAM4 to PmDAM6 responses to a short period of cold exposure appeared to vary between low-and high-chill genotypes. In the high-chill genotype, a short period of cold exposure slightly increased PmDAM4 to PmDAM6 expression, while in the low-chill genotype, the same treatment repressed PmDAM4 to PmDAM6 expression. Furthermore, PmDAM4 to PmDAM6 expression was negatively correlated with endodormancy release. We here discuss the genotype-dependent seasonal expression patterns of PmDAMs in relation to their involvement in endodormancy and variation in chilling requirements.
  • Hisayo Yamane, Tomomi Ooka, Hiroaki Jotatsu, Yukari Hosaka, Ryuta Sasaki, Ryutaro Tao
    JOURNAL OF EXPERIMENTAL BOTANY 62 10 3481 - 3488 2011年06月 [査読有り][通常論文]
     
    The present study investigated the expressional regulation of PpDAM5 and PpDAM6, two of the six peach (Prunus persica) dormancy-associated MADS-box genes, in relation to lateral bud endodormancy. PpDAM5 and PpDAM6 were originally identified as homologues of Arabidopsis SHORT VEGETATIVE PHASE/AGAMOUS-LIKE 24 identified in the EVERGROWING locus of peach. Furthermore, PpDAM5 and PpDAM6 have recently been suggested to be involved in terminal bud dormancy. In this study, seasonal expression analyses using leaves, stems, and lateral buds of high-chill and low-chill peaches in field conditions indicated that both genes were up-regulated during the endodormancy period and down-regulated with endodormancy release. Controlled environment experiments showed that the expression of both PpDAM5 and PpDAM6 were up-regulated by ambient cool temperatures in autumn, while they were down-regulated by the prolonged period of cold temperatures in winter. A negative correlation between expression levels of PpDAM5 and PpDAM6 and bud burst percentage was found in the prolonged cold temperature treatment. Application of the dormancy-breaking reagent cyanamide to endo/ecodormant lateral buds induced early bud break and down-regulation of PpDAM5 and PpDAM6 expression at the same time. These results collectively suggest that PpDAM5 and PpDAM6 may function in the chilling requirement of peach lateral buds through growth-inhibiting functions for bud break.
  • Yohei Higuchi, Kimiyo Sage-Ono, Ryuta Sasaki, Namie Ohtsuki, Atsushi Hoshino, Shigeru Iida, Hiroshi Kamada, Michiyuki Ono
    PLANT AND CELL PHYSIOLOGY 52 4 638 - 650 2011年04月 [査読有り][通常論文]
     
    GIGANTEA (GI) is a key regulator of flowering time, which is closely related to the circadian clock function in Arabidopsis. Mutations in the GI gene cause photoperiod-insensitive flowering and altered circadian rhythms. We isolated the GI ortholog PnGI from Pharbitis (Ipomoea) nil, an absolute short-day (SD) plant. PnGI mRNA expression showed diurnal rhythms that peaked at dusk under SD and long-day (LD) conditions, and also showed robust circadian rhythms under continuous dark (DD) and continuous light (LL) conditions. Short irradiation with red light during the flower-inductive dark period did not change PnGI expression levels, suggesting that such a night break does not abolish flowering by affecting the expression of PnGI. In Pharbitis, although a single dusk signal is sufficient to induce expression of the ortholog of FLOWERING LOCUS T (PnFT1), PnGI mRNA expression was not reset by single lights-off signals. Constitutive expression of PnGI (PnGI-OX) in transgenic plants altered period length in leaf-movement rhythms under LL and affected circadian rhythms of PnFT mRNA expression under DD. PnGI-OX plants formed fewer flower buds than the wild type when one-shot darkness was given. In PnGI-OX plants, expression of PnFT1 was down-regulated, suggesting that PnGI functions as a suppressor of flowering, possibly in part through down-regulation of PnFT1.
  • Noriko Tamura, Takahiro Yoshida, Arata Tanaka, Ryuta Sasaki, Asuka Bando, Shigeo Toh, Loic Lepiniec, Naoto Kawakami
    PLANT AND CELL PHYSIOLOGY 47 8 1081 - 1094 2006年08月 [査読有り][通常論文]
     
    Temperature is a primary environmental cue for seed germination of many weeds and vegetables. To investigate the mechanism of germination regulation by temperature, we selected five high temperature (thermoinhibition)-resistant germination mutants (TRW lines) from 20,000 T-DNA insertion lines of Arabidopsis. Segregation analyses indicated that each of the five lines had single locus recessive mutations. The seeds of TRW134-15 and TRW187 showed reduced sensitivity to ABA and also to the gibberrellin biosynthesis inhibitor, paclobutrazol. Genetic and nucleotide sequencing analyses indicated that TRW187 is a new allele of abi3 (abi3-14). TRW71-1 exhibited a maternal effect for both thermoinhibition-resistant and transparent testa phenotypes, and genetic analysis revealed that the mutation was allelic to tt7 (tt7-4 sib). Interestingly, the seeds of reduced dormancy mutants rdo1, rdo2, rdo3 and rdo4 were also thermoinhibition tolerant, and all the TRW seeds showed reduced dormancy. Like rdo3, TRW13-1 had shorter siliques and slightly shorter stems than the wild type. The mutation of TRW13-1 was mapped to the bottom arm of chromosome 1 where rdo3 has also been mapped, but the two mutants are not allelic. We designated TRW13-1 as thermoinhibition-resistant germination 1 (trg1). We also mapped the ABA-insensitive mutation of TRW134-15 to the bottom arm of chromosome 5 and named it trg2. These results show that both embryo/endosperm and maternal factors contribute to germination inhibition at supraoptimal temperatures in Arabidopsis. In addition, we confirm the role of ABA in thermoinhibition of seed germination and a link between seed physiological dormancy and response to high temperature.

その他活動・業績

  • 羽生 剛, 山根 久代, 佐々木 隆太, 矢野 健太郎, 藤井 浩, 清水 徳朗, 山本 俊哉, 田尾 龍太郎 Journal of the Japanese Society for Horticultural Science 83 (1) 1 -16 2014年01月 [査読無し][通常論文]
     
    永年性作物において越冬芽の休眠は,環境に適応するために進化した成長制御機構のひとつであり,かつ翌年の成長を左右する重要な農業形質のひとつである.芽の休眠には多くの遺伝的要因が関わるばかりでなく,多岐にわたる環境要因や樹勢,樹齢の影響もうけており,多くの遺伝子の発現制御が休眠に関与していると考えられる.そこで本研究では,休眠関与候補遺伝子の単離を目的に,カスタムマイクロアレイを用いたウメ休眠芽のトランスクリプトーム解析をおこなった.まず,我々が先行研究で獲得したウメ芽 EST 配列情報をもとに,ゲノム全体をできるだけ偏りなく網羅するように選びだした 58539 ユニジーンに相当するプローブを搭載したマイクロアレイを構築した.次いで,休眠覚醒を誘導する長期の低温処理を施したウメ休眠芽の遺伝子発現変動を調査した.その結果,有意に 2 倍以上発現が上方制御あるいは下方制御されるプローブが 2345 個あるいは 1059 個同定された.これらの変動遺伝子のなかには季節的な発現同調性がみられるものがあった.下方制御される遺伝子のなかには,先行研究で休眠への関与が示唆されている DORMANCY ASSOCIATED MADS-box が含まれており,上方制御される遺伝子にはリポキシゲナーゼが含まれていた.Parametricanalysis of gene set enrichment 解析の結果,長期の低温遭遇によってジャスモン酸やオキシリピン生合成・代謝の GO タームが有意に上昇し,概日リズムの GO タームが有意に減少した.これらの GO タームに含まれる遺伝子について定量 RT-PCR を行った結果,マイクロアレイで検出された発現変動パターンとほぼ同様であった.以上の結果より,本研究で構築したマイクロアレイはウメ休眠芽の網羅的な遺伝子発現解析に有効であることが示された.本実験では,ウメの休眠覚醒に関与する遺伝子ネットワークあるいは新規候補遺伝子の探索に活用した.
  • Hisayo Yamane, Ryutaro Tao, Tomomi Ooka, Hiroaki Jotatsu, Ryuta Sasaki, Keizo Yonemori JOURNAL OF THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE 80 (3) 276 -283 2011年07月 [査読無し][通常論文]
     
    This study investigated the regulation of the seasonal expression of PpDAM5 and PpDAM6, two of the six peach (Prunus persica) dormancy-associated MADS-box genes, in relation to the endodormancy and development of lateral vegetative and flower buds of low- and high-chill peach cultivars. PpDAM5 and PpDAM6 were originally found as homologs of Arabidopsis SVP/AGL24 at the EVERGROWING (EVG) locus of peach and have been recently shown to be involved in lateral bud endodormancy. Seasonal expression analyses in this study indicated that PpDAM5 and PpDAM6 transcript levels in lateral vegetative buds of both low- and high-chill cultivars in the field negatively correlated with bud burst percentages determined under forcing conditions. Negative correlation was also found between their transcript levels and the flower organ enlargement rate. These results suggest that distinct seasonal expression patterns of PpDAM5 and PpDAM6 are correlated with a distinct chilling requirement for bud break and flowering of low- and high-chill cultivars. Characterization of the genomic structure of PpDAM5 and PpDAM6 revealed the presence of large insertions in the first introns of both PpDAM5 and PpDAM6 in low-chill peach. Alteration of the genomic structure is discussed with respect to the low-chill character.


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