鎘及高溫調控水稻幼苗ABA生合成分子機制之研究

Abstract

鎘及高溫逆境會嚴重限制植物的生長及產量。過去的研究顯示，常溫下 (日溫30℃/夜溫25 ℃)，鎘逆境使得耐鎘水稻TNG67的根部及葉片比不耐鎘水稻TCN1累積較高含量的ABA，而在高溫 (日溫35 ℃/夜溫30 ℃)與鎘的雙重逆境下，TNG67及TCN1則都會在葉片中累積高含量的ABA。為了瞭解鎘及高溫逆境對水稻ABA生合成的調控機制，本試驗以阿拉伯芥基因為藍本，經由生物資訊學的方法找出水稻中ABA生合成相關的基因，並分析這些基因對鎘及高溫的反應。試驗中一共找出2個ZEP基因、13個NCED基因、3個SDR基因、及5個AAO基因。半定量RT-PCR分析結果顯示，各基因家族在TNG67不同組織間多具有不同的表現量。TNG67及TCN1的葉片及根部對鎘及高溫有不同的反應。在葉片中，所有OsZEPs與OsAAOs的表現都不受鎘及高溫的影響，但一些OsNCEDs (OsNCED1、OsNCED2、OsNCED3、OsNCED5及OsCCD8b)、及OsSDRs (OsSDR2及OsSDR3)，則有差異表現。在根部中，OsZEPs (OsZEP1a及OsZEP1b)、OsNCEDs (OsNCED1、OsNCED2、OsNCED3、OsNCED5、OsNCED6、OsNCED7、OsCCD1及OsCCD8b)、OsSDR3、及OsAAOs (OsAAO3及OsAAO4)等基因，在鎘、高溫或高溫加鎘雙重逆境下，分別受到不同程度的調控。這些結果顯示，耐鎘與對鎘敏感水稻在鎘逆境或高溫逆境下，葉片及根部ABA生合成具有不同但複雜的調控機制。

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.