中文摘要
近年来，表观遗传学研究成为生命科学的热点领域。组蛋白，作为染色体基本单位-核小体的核心组成部分，其修饰是重要的表观遗传学修饰之一。一般认为，组蛋白H3K4和H3K36的甲基化修饰与基因转录激活有关。然而关于它们的研究在植物中却相当有限，在水稻中更是一片空白。我们的主要研究对象SDG725，在体外具有H3K36专一性的甲基转移酶活性。通过RNAi及amiRNA方法，我们获得了多个SDG725功能缺失的水稻突变体。sdg725突变株表型多效，表现为植株整体矮小、包茎、剑叶夹角变小等。在sdg725突变株中，一些与油菜素内酯（BR）合成及与信号传导相关的基因在转录水平上发生改变。通过染色质免疫沉淀我们发现突变体中这些下调基因染色质区段的H3K36甲基化修饰发生了明显的下降，相对应的，SDG725与这些靶基因的结合也出现了下降。因而我们的研究首次报道了水稻中一个有活性的组蛋白H3K36甲基转移酶，并且揭示了组蛋白H3K36的甲基化修饰对于基因表达及其植物生长发育的重要作用。
英文摘要
Recently, study in chromatin modifications has become a hot research topic. Histones, as the structural core of the nucleosome, are subject to multiple types of covalent modifications. Histone lysine methylation plays an essential role in epigenetic regulation of gene expression in eukaryotes. While enzymes involved in the establishment of the repressive H3K9 and H3K27 methylation marks have been previously characterized, deposition and function of H3K4 and H3K36 methylations remain yet uncharacterized in rice. In this study, we report that rice SDG725 encodes a H3K36 methyltransferase and its down-regulation causes wide-ranging defects, including dwarfism, shortened internodes, erect leaves, and small seeds. These defects resemble the phenotypes previously described for some brassinosteroid (BR)-knockdown mutants. Consistently, transcriptome analyses revealed that SDG725-depletion results in down-regulation by more than two-fold of over a thousand of genes, including D11, BRI1 and BU1, which are known to be involved in BR biosynthesis or signaling pathways. Chromatin immuno-precipitation (ChIP) analyses showed that levels of H3K36me2/3 are reduced in chromatin at some regions of these BR-related genes in SDG725-knockdown plants and that SDG725 protein was able to directly bind at these target genes. Taken together, our data indicate that the SDG725-mediated H3K36 methylation modulates BR-related gene expression, playing an important role in rice plant growth and development.
结题摘要
近年来，表观遗传学研究成为生命科学的热点领域。组蛋白，作为染色体基本单位-核小体的核心组成部分，其修饰是重要的表观遗传学修饰之一。一般认为，组蛋白H3K4和H3K36的甲基化修饰与基因转录激活有关。然而关于它们的研究在植物中却相当有限，在水稻中更是一片空白。我们的主要研究对象SDG725，在体外具有H3K36专一性的甲基转移酶活性。通过RNAi及amiRNA方法，我们获得了多个SDG725功能缺失的水稻突变体。sdg725突变株表型多效，表现为植株整体矮小、包茎、剑叶夹角变小等。在sdg725突变株中，一些与油菜素内酯（BR）合成及与信号传导相关的基因在转录水平上发生改变。通过染色质免疫沉淀我们发现突变体中这些下调基因染色质区段的H3K36甲基化修饰发生了明显的下降，相对应的，SDG725与这些靶基因的结合也出现了下降。因而我们的研究首次报道了水稻中一个有活性的组蛋白H3K36甲基转移酶，并且揭示了组蛋白H3K36的甲基化修饰对于基因表达及其植物生长发育的重要作用。