| Summary: | 碩士 === 臺灣大學 === 農業化學研究所 === 95 === Cadmium (Cd) and high temperature are limiting factors of plant growth and yield. Previous studies demonstrated that Cd stress increased the accumulation of ABA in Cd-tolerant cultivar TNG67 under normal temperature condition 30 ℃/25 ℃ (day /night), while no significant change was observed in Cd-sensitive cultivar TCN1 in both leaf and root tissue. On the other hand, with treatment of Cd and high temperature 35 ℃/30 ℃ (day /night), ABA was shown to highly accumulated in leaves of TCN1 and TNG67. To dissect the molecular mechanisms affecting ABA accumulation under Cd and high temperature stresses in rice seedling, this study identified ABA biosynthetic genes by bioinformatics approach, and gene expression patterns were analyzed by semi-quantitative RT-PCR. Totally, 2 ZEP genes, 13 NCED genes, 3 SDR genes, and 5 AAO genes were identified. Gene expression analysis revealed that genes of each gene family differentially expressed in different tissues. ABA biosynthetic genes showed different expression patterns to Cd and high temperature between Cd-tolerant cultivar TNG67 and Cd-sensitive cultivar TCN1. In leaf tissue, OsZEPs and OsAAOs did not response to Cd and high temperature stresses, but some genes of OsNCEDs (OsNCED1, OsNCED2, OsNCED, OsNCED5, OsCCD8b), and OsSDRs (OsSDR2 and OsSDR3) were regulated by Cd and high temperature. In root tissue, expression of OsZEPs (OsZEP1a and OsZEP1b), OsNCEDs (OsNCED1, OsNCED2, OsNCED3,OsNCED5, OsNCED6, OsNCED7, OsCCD1 and OsCCD8b), OsSDR3 and OsAAOs (OsAAO3 and OsAAO4) were regulated by Cd, high temperature, or Cd plus high temperature stresses. Taken together, our data reveals that under Cd, high temperature or Cd plus high temperature conditions, leaf or root tissue of TCN1 and TNG67 have diverse regulatory modes controlling the biosynthesis of ABA.
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