水稻组蛋白H3K36甲基转移酶SDG708调节干旱胁迫响应的分子机制研究

Histone H3K36 methylation is an important epigenetic modification, involved in many biological processes, such as transcription elongation, alternative splicing, DNA repair and plant flowering regulation. The applicant is in a laboratory which focuses studying histone H3 lysine 36-specific methylation for more than ten years. SET DOMAIN GROUP 708, a histone H3 lysine 36-specific methyltransferase, controls flowering time in rice. It’s particularly interesting that many drought stress response genes were mis-regulated in SDG708 down-regulated rice. Rice (Oryza Sativa) is one of the most leading cereal crops, the yield of which will be strongly affected by drought stress. We find that SDG708 knock-down (708Ri) rice plants were sensitive to drought stress while those overexpressing SDG708 were more tolerant to drought treatment. Consistently, 708Ri plants showed higher rate of water loss and more open stomas than the wild-type plants did and the overexpression of SDG708 displayed the opposite phenotypes. We aim to analyze the biological function of SDG708 in rice drought stress response using the techniques of genetics, biochemistry, molecular biology and bioinformatics.

组蛋白H3K36甲基化是一种重要的表观遗传修饰，参与包括转录延伸、选择性剪切、DNA修复、植物开花等多项生命进程。申请人所在实验室长期从事水稻H3K36甲基化修饰对植物生长发育的调控研究。前期研究证明了H3K36甲基转移酶SDG708参与到水稻的开花调控过程中，此外通过RNA-seq数据分析表明SDG708的下调会引起一系列干旱调控基因的表达改变。水稻作为世界上最主要的粮食作物，干旱胁迫严重的影响水稻终产量。我们最新的研究发现SDG708下调突变体表现出对干旱胁迫敏感而其过量表达植株表现出抗旱的表型，与之对应的是突变体较野生型失水率高、干旱处理后气孔不易闭合；而过量表达材料则表现相反的表型。本项目计划利用遗传学，生物化学与分子生物学以及生物信息学等研究手段，通过RNA-seq、ChIP-seq数据及蛋白互作的分析，探索SDG708以及H3K36甲基化修饰在植物抗旱过程中的功能。

组蛋白修饰在植物对于外界非生物胁迫的响应中发挥着重要的作用，但是组蛋白H3第36位赖氨酸甲基化修饰在水稻的干旱胁迫中的作用却没有报道。本项目以水稻H3K36甲基转移酶SDG708作为研究对象，我们发现SDG708是水稻中干旱胁迫的正调控因子，即SDG708突变体不抗旱，SDG708过表达水稻抗旱。随后的研究发现SDG708通过直接结合脱落酸ABA合成基因OsNCED3以及OsNCED5促进两者表达从而提高体内的ABA含量。此外，SDG708还能够诱导保卫细胞中过氧化氢的积累从而促使气孔关闭，进而保水。过表达SDG708能够显著提高在正常条件以及干旱条件下的水稻产量。因此，SDG708是一个潜在的能够提高水稻产量的表观遗传因子。