拟南芥中不依赖于DNA甲基化水平变化的转录水平基因沉默机制研究

DNA甲基化是一种重要的表观遗传修饰，在基因的表达调控、基因组的结构及稳定性等方面都具有十分重要的作用。除了改变DNA甲基化水平，越来越多的证据表明染色质结构的改变也会影响转录水平的基因沉默。然而染色质高级结构如何参与植物基因转录水平的调控以及DNA甲基化与染色质高级结构如何协同作用共同调控植物基因组的稳定性的分子机制还不清楚。本研究在前期工作的基础上，进行了大规模的idm1-14抑制子的筛选。我们鉴定到了两类突变体：第一类突变体中DNA甲基化水平明显降低，而第二类突变体的甲基化水平则没有明显的变化。通过对突变体进行图位克隆和全基因组重测序，我们除了克隆到已知的参与DNA甲基化和染色质结构维持的基因以外，还鉴定到几个新的基因。本项目将对其中的一个基因SOI3进行详细的功能研究，阐明其在基因沉默过程中的功能，推进基因沉默机制尤其是DNA甲基化下游参与基因沉默机制的研究。

DNA methylation is an important epigenetic modification and plays important roles in the regulation of gene expression and genome stability. Besides alternations in DNA methylation, alterations in the chromatin architecture also results in changes in gene expression at the transcriptional level. However, how the higher order chromatin structure regulates gene expression and how DNA methylation and chromatin architecture function coordinately in the maintenance of genome stability remain unknown. In this study, we performed a genetic screening to identify the suppressors of IDM1 using a luciferase (LUC) line in the idm1-14 background. We isolated multiple mutants with higher levels of 35S promoter-driven luciferase (LUC) luminescence. One group of mutants have impaired DNA methylation levels but another group of mutants do not exhibit changes in DNA methylation levels. Through map-based cloning, we cloned several new genes involved in transcriptional gene silencing (TGS) beside lots of well-known genes involved in establishing DNA methylation and maintaining higher order chromatin architecture. We will specifically study the molecular function of SOI3 in TGS. Our work will shed light on the mechanisms that exist for plant cells to silence genes.