DNA甲基化是重要的表观遗传修饰,可以调控植物的生长发育与逆境响应等生命过程。RdDM(RNA指导的DNA甲基化)途径是介导DNA从头甲基化主要的分子途径。本项目利用我们所独有的遗传筛选体系分离和鉴定出水稻表观遗传突变体des1，在突变中沉默的转基因恢复超表达，图位克隆表明DES1编码一个RNA依赖的RNA聚合酶。与同源基因RDR2在RdDM中的作用不同，DES1可能通过siRNA不依赖的途径调控35S启动子上CG,CHG类型的DNA甲基化,维持转基因沉默。des1突变体影响了水稻的株型，穗型、粒型、育性等重要的农艺性状的发育，表明其可能在全基因组水平上调控基因的表达。本项目将在此基础上，利用遗传学和基因组学等手段阐明DES1介导DNA甲基化的建立与维持、调控基因表达的分子机制，并鉴定出DES1调控水稻株高、穗型和粒型发育的靶基因，并解析其表达调控的分子机制。

DNA methylation is an epigenetic mark that regulates plants development and growth, adaptation to various stresses. RNA-directed DNA Methylation is the main de novo DNA methylation pathway in plants. In this proposal, we use special genetic screen system to isolated and characterized an epigenetic silencing mutant, des1 in which the silenced gene restore to overexpression. Map-based cloning demonstrated that DES1 encode a RNA-dependent RNA Polymerase. DES1 might regulate the CG and CHG methylation on 35S promoter in a siRNA independent manner, eventually maintained gene silencing, which is inconsistent with the role of RDR2 in RdDM pathway. More importantly, the mutation in DES1 changed diverse agricultural traits formation including plant architecture, panicle architecture, grain size and fertility, which imply it regulating gene expression on whole genome scale. In this proposal, we will use genetics, genomics tools to decode the mechanism of DES1 mediating DNA methylation and regulating gene expression, to reveal the molecular genetic basis of DES1 controlling the development of plant height, panicle architecture and grain size.