寻找光信号途径的调控因子对阐述光调控植物生长发育的分子机理有重要意义。我们通过正向遗传学手段筛选获得了一个光形态建成增强的突变体epp2（enhanced hotomorphogenic2）。epp2突变体在红光、远红光及蓝光下下胚轴均比野生型短。经图位克隆，EPP2可能编码一个转录辅助因子。Co-IP/MS结果表明EPP2与一个未知功能的E3泛素连接酶U1互作，U1可能介导EPP2的降解。另外，EPP2与光信号关键因子PIF4也互作。转录组结果表明，EPP2与PIF4共同调控很多基因表达，包括生长素通路相关基因。另外，PIF4发挥功能有可能部分依赖于EPP2。本项目拟采用分子生物学、生物化学、遗传学和细胞生物学等研究手段，探究EPP2的生化功能，阐释EPP2与PIF4互作机理，以期阐明EPP2与PIF4在调控光形态建成与生长素信号转导中的作用，为不同信号网络的互作提供新的见解。

Identification of new regulatory factors in the light signaling pathway is of important for elaborating the molecular mechanisms underlying plant growth and development. We obtained a photomorphogenesis-enhanced mutant epp2 using forward genetics approach. By map-based cloning, we cloned the EPP2 gene which encode a putative transcriptional cofactor. Overexpression of EPP2 could rescue the short.hypocotyl phenotypes of the epp2 mutant. Co-IP/MS experiment showed that EPP2 interact with an E3 ubiqutin ligase U1 with unknown function and U1 might mediate protein degradation of EPP2. EPP2 interact with PIF4, a key factor involved in light signaling. Whole Transcriptome Sequencing results showed that EPP2 and PIF4 could co-regulate the expression of a lot of genes, including the auxin-responsive gene family. By using the approaches of molecular biology, biochemistry, genetics and cell biology, we propose to investigate the biochemical function of EPP2.We will explor the mode of action and the molecular mechanism of between EPP2 and PIF4. The purpose of this study is to clarify the function of EPP2 and PIF4 in the light signaling and auxin pathway. We believe that this study will identify a new factor of the light signaling pathway and provide new insight into the mechanism that different signaling networks interact.