高等植物在黑暗和光照条件下会展现两种截然不同的形态，其调控机理研究对了解植物生长发育调控有重要意义。我们前期实验筛选获得蓝光诱导基因SRS5过表达突变体SRSox。SRSox在黑暗条件下表现出光形态建成表型,而在蓝光下srs5下胚轴比野生型长。双突变分析表明，SRSox的短下胚轴在SRSox hy5和SRSox sth3中被部分回复；而且SRS5能调控HY5和STH3的表达。此外，初步ChIP-PCR表明SRS5能结合到STH3的启动子区；酵母双杂交显示COP1能与SRS5互作。我们计划进一步验证SRS5在光形态学建成中的作用，检验HY5和STH3是否为SRS5的直接下游并深入了解它们间的协同关系，探究SRS5是否受COP1介导的泛素化降解途径调控,通过回复突变体的深入分析获得其它因子。研究结果将明确证明转录因子SRS5参与调控光形态学建成，并明晰其在蓝光介导的光形态建成中如何发挥作用。

Higher plants exhibit two distinct morphogenesis in dark and light, and the knowledge of the underlying mechanisms is important for us to understand how plants cope with environment and choose the appropriate morphogenesis. By screening Arabidopsis mutant library, a mutant SRSox, in which SRS5 is over-expressed, exhibits photomorphogenesis in dark. Our further study demonstrated that blue light induces SRS5 expression. Under blue light, SRSox has shorter hypocotyl compared with wild-type, while the knock-out mutant (srs5) shows higher hypocotyl than wild-type. In addition, the phenotype of short hypocotyls in SRSox is partially rescued in two double mutants SRSox hy5 and SRSox sth3. Furthermore, while the expression of HY5 and STH3 is induced in SRSox, they are repressed in srs5, suggesting that HY5 and STH3 function in SRS5-mediated photomorphogenesis. Also, ChIP-PCR experiments indicated that SRS5 may bind to STH3 promoter and yeast two-hybrid showed possible interaction of COP1 and SRS5. In this project, we plan to carry our further experiments to demonstrate that SRS5 plays an important role in blue light-mediated photomorphogeneses. The project will explore whether SRS5 directly regulates the expression of HY5 and STH3 and identify its binding motifs, indicate that HY5 and STH3 are essential for SRS5-mediated photomorphogenesis, investigate a role of COP1-mediated ubiquitin degradation pathway for SRS5 stabilization, and isolate other factors involved in SRS5-meidated photomorphogeneses. Taken together, our findings will show how SRS5 modulates blue light-mediated photomorphogeneses and enhance our understanding of the mechanisms underlying light-regulated plant morphogenesis.