Clp蛋白酶系统参与叶绿素降解代谢关键酶蛋白降解的机制研究

叶片发育成熟后会响应体内外相应因子的变化可逆地启动衰老褪绿进程，这一灵敏的响应能力对于植物灵活地调整其生存策略至关重要，然而其中的分子机制依然知之甚少。编码叶绿素降解关键代谢酶（CCEs）的基因（CCGs）已经先后被克隆；在转录水平上，以NYE1为代表的CCGs的表达受到严格调控；然而，CCEs在蛋白水平上的调控机制却鲜有探索。前期分析表明，NYE1蛋白能够响应环境或发育相关因子的变化而快速合成或降解；本项目拟通过解析NYE1蛋白的降解特性并鉴别相关降解酶，阐明候选Clp蛋白酶降解NYE1的分子机制，探索Clp蛋白酶参与其它CCEs降解的可能性，系统阐明主要CCEs的降解机制。预期结果不仅有助于理解叶绿素降解的多层级精准调控机制，也有助于理解衰老进程中叶绿体内降解代谢酶蛋白的降解机理；通过探索Clp蛋白酶参与CCEs蛋白的降解机制，还有助于阐明Clp蛋白酶在植物生长发育过程中的多样性功能。

Mature leaves can swiftly yet reversibly initiate senescence in responding to the changes of internal and/or external factors, with the degradation or re-biosynthesis of chlorophyll (Chl) as being the most significant molecular phenotype; and the swiftness of the response is vital to the survivability of plants. However, little is known about the underlying mechanisms. Over the last decade or so, the major biochemical pathway of Chl degradation has been largely revealed by identifying Chl catabolic genes (CCGs), and substantial progress made in elucidating the regulatory mechanisms of their transcription. However, the regulation of the protein abundance of Chl catabolic enzymes (CCEs) is seldom explored. Recently, we found that NYE1 protein could be rapidly degraded in response to the changes of environmental or developmental signals, but the molecular mechanism underlying is not clear. In this project, we plan to investigate the following issues: 1) to analyze the degradation characteristics of NYE1 protein and identify the related protease of NYE1 protein, 2) to elucidate the molecular mechanism by which the candidate Clp protease degrades NYE1, and 3) to explore the possible involvement of Clp protease in catalyzing the degradation of other major CCEs. By doing these, we expect to understand more about the complex/multi-layered/precise regulatory mechanisms of Chl degradation during leaf senescence. At the same time, we also expect to reveal more diverse functions of Clp protease in modulating plant growth and development.