Reciprocal regulation of chloroplast protein synthesis and carbon metabolism for thylakoid membrane biogenesis

类囊体膜代表高度发达的光合能量转导部位。它们的生物生成需要脂质和蛋白质的合成。然而，关于这两种生物合成途径是否以及如何在分子水平上相互联系，人们知之甚少。众所周知，叶绿体丙酮酸脱氢酶复合体可以产生用于脂肪酸和脂质合成的活性碳前体分子（乙酰辅酶a）。我们的前期工作表明，该酶的DLA2亚基也是核糖核蛋白复合物的一个组成部分，并且在绿藻模型系统莱茵衣藻的叶绿体mRNA翻译的空间组织中起作用。相反，RNA结合会影响丙酮酸脱氢酶的活性。这些发现为胞内代谢信号和叶绿体基因表达如何在类囊体膜生物发生中相互联系提供了第一个线索。此外，我们的数据提供了第一个提示，这些蛋白质的双重作用可能存在于从蓝藻到人类的进化遥远的生物体中。在本项目中，我们旨在阐明这种涉及基因表达代谢控制的调控原理的精确分子工作模式。通过对莱茵梭菌的分子、遗传和生化研究，我们将使用体内和体外技术来表征DLA2的RNA结合和酶促形式，DLA2似乎在不同的蛋白质亚复合物之间穿梭。特别关注这些复合物的动力学和组成，以及醋酸/乙酰辅酶A在平衡DLA2的两种功能方面的作用。这项工作将通过蓝藻和高等植物的相关分析来补充，以测试这种调节开关的进化保护。

Thylakoid membranes represent highly developed sites for photosynthetic energy transduction. Their biogenesis requires the synthesis of both lipids as well as proteins. However, little is known regarding if and how these two biosynthetic pathways are interconnected at the molecular level. The chloroplast pyruvate dehydrogenase complex is well-known to produce activated di-carbon precursor molecules (acetyl-CoA) for fatty acid - and as a consequence - lipid synthesis. Our prework shows that the DLA2 subunit of this enzyme is additionally a component of a ribonculeoprotein complex and as this has a function in the spatial organization of chloroplast mRNA translation in the green algal model system Chlamydomonas reinhardtii. Conversely, RNA binding affects pyruvate dehydrogenase activity. These findings provide a first clue regarding how intraplastidic metabolic signaling and chloroplast gene expression could be reciprocally connected for thylakoid membrane biogenesis. In addition, our data provide first hints that these dual roles of the protein might exist in evolutionary distant organisms ranging from cyanobacteria to humans.In this project, we aim at elucidating the precise molecular working mode of this regulatory principle involving metabolic control of gene expression. By following molecular, genetical, and biochemical approaches in C. reinhardtii, we will use in vivo and in vitro techniques to characterize both the RNA binding and the enzymatic forms of DLA2 which appears to shuttle between different protein sub-complexes. A special focus will be on the dynamics and composition of these complexes and the role of acetate/acetyl-CoA for balancing both functions of DLA2. This work will be complemented by related analyses in cyanobacteria and higher plants, to test for an evolutionary conservation of such a regulatory switch.