拟南芥多梳蛋白复合体是调控基因表达，维持细胞属性的重要染色质修饰因子。其通过调控组蛋白H3K27位点的甲基化修饰和H2A的泛素化修饰引发目标基因区段的染色质发生凝缩，从而抑制基因表达。多梳蛋白复合体成员不具有DNA序列的选择特异性，其对目标基因的修饰需要转录因子介导。因此，寻找引导其参与某一特定生物学过程的转录因子就成为表观遗传学研究的热点。我们前期对复合体中的LHP1蛋白进行酵母双杂交筛库，发现并验证了它与植物激素油菜素内酯信号通路下游转录因子BZR1和BIM1相互作用。lhp1突变体自身呈现BR缺失表型，并对BR抑制剂超敏感，提示LHP1可能参与BR信号通路的正向调控。遗传实验表明LHP1对BR通路的调控依赖于BZR1和BIMs。申请人拟在此基础上，探明多梳蛋白复合体及其调控的表观遗传修饰在油菜素内酯信号通路中所起的生物学功能和分子作用机制。

The evolutionarily conserved genome-wide gene silencing by Polycomb group (PcG) proteins is essential for the maintenance of cell identity and the growth and development of multicellular organisms in both plants and animals. PcG proteins can be sub-divided into two complexes, Polycomb Repressive Complex 1 (PRC1) and PRC2. PRC2 deposits the repressive mark, histone H3K27me3, at target loci, which is recognized by PRC1. In addition, PRC1 deposits another histone marker H2Aub which cooperates with H3K27me3 and leads to the chromatin compaction and gene silencing. The PcG components have no DNA binding specificity, therefore, an important question is how the Polycomb epigenetic machinery recognizes the target gene for its silencing. Recent studies in both animals and plants pointed out that transcription factors (TFs) bind to specific cis-regulatory regions (Polycomb response elements, PREs) and recruit PcG proteins to the target genes. To look for the TFs which involve in specific biological function and direct PcG to the gene loci, the yeast two hybrid library screening was applied by using Arabidopsis PcG component LHP1 as a bait. Among the potential candidates, we verified that two TFs in Brassinosteroid signaling pathway, BZR1 and BIM1, can interact with LHP1 in vivo. lhp1 mutant is small and has several side branches, which is similar to the BR-deficient and -insensitive mutants. Moreover, lhp1 is hypersensitive to the BR inhibitor BRZ in dark-grown conditions, indicating that LHP1 may act as a positive regulator in BR transduction. Genetic studies also found out that the role of LHP1 in BR signaling pathway depends on BZR1 and BIMs, corresponding to the protein interactions. Based on this, we plan to identify the biological function of PcG proteins in BR signaling pathway and to explore its underlying molecular mechanism. In addition, whether PcG proteins involve in the crosstalk between BR and other hormone and how it works will also be illustrated in this study. We hope to uncover the epigenetic regulation of plant hormone signaling pathway and shed light on the interconnection of the two fundamental regulation of gene transcription.