Nitrogen-starvation induced chlorosis in cyanobacteria: A proteolytic program for maintenance of viability

当非重氮营养蓝藻被剥夺联合氮源时，细胞降解其光合色素的过程称为褪绿。以前，我们已经表明，细胞的漂白是一个简单的发育程序的一部分，其特征是代谢活性的顺序衰减和几乎所有细胞蛋白质的逐步降解，直到目前尚未确定的蛋白质水解活性接近完成。它导致细胞能够在非生长条件下以休眠状态存活不确定的长时间。在这个项目中，我们想分析黄化的蛋白水解过程。首先，我们将着重于鉴定导致黄化的蛋白酶和相关因素。下一步将研究蛋白质水解的调控：哪些信号启动蛋白质水解过程，蛋白质如何依次靶向蛋白质水解，如何控制蛋白酶以防止基本活性的完全降解？我们采用模式生物聚胞菌PCC 6803，其基因组数据可用，并建立了分子生物学方法。实验方法包括蛋白质组和转录组分析、分子遗传学、生化和生理分析。广泛的实验方法需要在优先规划内进行密切合作。

When non-diazotrophic cyanobacteria are deprived of combined nitrogen sources, cells degrade their photosynthetic pigments in a process termed chlorosis. Previously, we have shown that bleaching of the cells is part of a simple developmental program which is characterized by the sequential decay of metabolic activitiy and the stepwise degradation of almost all cellular proteins to near completion by so far unidentified proteolytic activities. It results in cells that are able to survive for undefined long periods under non-growing conditions in a dormant state. In this project we want to analyze the proteolytic process underlying chlorosis. Initially, we will focus on the identification of proteases and related factors which carry out chlorosis. In a next step regulation of proteolysis will be studied: which signals initiate the proteolytic process, how are the proteins sequentially targeted to proteolysis, how are the proteases controlled to prevent a complete degradation of essential activities? We employ the model organism Synechocystis PCC 6803, for which the genome data are available and for which molecular biology methods are established. Experimental approaches include proteome and transcriptome analyses, molecular genetics, biochemical and physiological analyses. The broad experimental approach requires intensive collaboration within the priority program.