OPR Protein-mediated Control and Adaption of Chloroplast Gene Expression in Chlamydomonas

由于叶绿体的内生起源，构成类囊体膜多亚单位复合体的许多蛋白质现在编码在细胞核中，而其他蛋白质则编码在叶绿体本身。因此，叶绿体基因的表达需要与核基因的表达相协调，以允许蛋白质复合体的平衡组装。此外，细胞器的基因表达需要适应不断变化的环境，特别是光，以满足细胞的需求。到目前为止，八肽重复蛋白(OPR)作为绿藻叶绿体基因转录后调控的关键角色才刚刚出现。由藻类基因组编码的大多数OPR的RNA靶标及其分子工作模式尚不清楚。此外，OPR与其叶绿体靶标RNA的特异性相互作用使其成为叶绿体基因表达的理想候选者，以适应不断变化的光条件。由于光系统II(PSII)对光损伤最敏感，因此本项目的重点是在模式生物莱茵衣藻中发现具有PSII亚单位表达功能或预期功能的OPR。为了进一步深入了解OPR对叶绿体基因表达的调控，我们旨在(I)阐明参与稳定两个编码PSII亚单位的mRNAs的确切分子工作模式，(Ii)识别参与PSII生物发生的新的OPR，以及(Iii)研究这些OPR对细胞器依赖光的适应过程的影响。

Due to the endosymbiotic origin of chloroplasts, many of the proteins constituting the multisubunit complexes of the thylakoid membrane are nowadays encoded in the nucleus while others are encoded in the chloroplast itself. Chloroplast gene expression therefore needs to be coordinated with the nuclear one to allow a balanced assembly of protein complexes. In addition, gene expression of the organelle requires an adaption to a changing environment, in particular light, to meet the demand of the cell. To date, the predominant role of Octotricopeptide Repeat proteins (OPRs) as key players for the posttranscriptional control of chloroplast gene expression in green algae is just emerging. The RNA targets of the majority of OPRs encoded by the algal genome as well as their molecular working modes are unknown. Moreover, the specific interaction of OPRs with their plastid target RNAs makes them ideal candidates as regulators of chloroplast gene expression for an adaption to changing light conditions. As photosystem II (PSII) is most susceptible to photodamage, the focus of the proposed project lies on OPRs with confirmed or expected functions in the expression of PSII subunits in the model organism Chlamydomonas reinhardtii. To gain further important insights into the OPR-mediated control and regulation of chloroplast gene expression, we aim at (I) elucidating the precise molecular working mode of two OPRs involved in the stabilization of two mRNAs encoding PSII subunits, (II) identify new OPRs involved in PSII biogenesis and (III) investigate the impact of these OPRs on light-dependent adaptive processes of the organelle.