The significance of photosystem II supercomplexes in light acclimation of Arabidopsis thaliana

光合作用是地球上主要的能量固定过程。高等植物以拟南芥为模式植物，通过快速、高效地调节自身的光合作用能力，从而在保证高光合作用的同时，保护其免受氧化损伤。光系统(PS)II超复合体对光合作用的调节具有重要意义。虽然PSII超复合体的结构已经确定，但对光习服过程中PSII超复合体的组装和重塑过程知之甚少。我们在以前的工作中发现，PSII相关蛋白Psb27是组装和/或稳定PSII超复合体所必需的，而PSII超复合体的重构是由PSII核心蛋白磷酸化诱导的。有趣的是，PSII亚单位CP43的主要磷酸化位点可能是Psb27结合位点。在这个项目中，我们的目标是阐明PSII超复合体的组装和调控。为此，i)我们将利用免疫生化方法来确定PSII相关因子Psb27的定位和功能。此外，我们将在植物中使用标记Psb27的品系来鉴定相互作用的蛋白质。Ii)我们将研究PSII核心磷酸化的动力学与PSII超复合体功能改变的关系。用荧光计量学和光谱学的方法，我们将评估伴随而来的光收集、光能分布和传输的变化。为此，我们将使用具有改变的类囊体复合体磷酸化的突变系，并结合定义的光区域。通过这种方法，我们将能够指定差异磷酸化的PSII超复合体的生理功能。Iii)我们将利用PSII超复合体组装或调节受损的拟南芥品系，研究PSII重塑对适应不同光环境能力的生理影响。这些突变体将受到波动光条件的影响，并测试它们的光合作用性能。关于PSII超复合体及其重塑的知识将使我们能够评估光环境对植物生长和产量的影响。在未来，农业重要植物的生产力可能会从这一知识中受益。

Photosynthesis is the major energy fixing process on earth. Higher plants as the model plant Arabidopsis thaliana regulate their photosynthetic capacity very fast and efficiently in order to allow for high photosynthetic performance and at the same time protection from oxidative damage. Photosystem (PS) II supercomplexes are of substantial importance for regulation of photosynthesis. Although the structure of PSII supercomplexes has been determined, the process of PSII supercomplex assembly and PSII supercomplex remodeling during light acclimation is poorly understood. We revealed in own previous work that the PSII associated protein Psb27 is required for assembly and/or stability of PSII supercomplexes while PSII supercomplex remodeling is induced by PSII core protein phosphorylation. Interestingly, the major phosphorylation site of the PSII subunit CP43 might be a putative Psb27 binding site. Within this project we aim to elucidate the assembly and regulation of PSII supercomplexes. To this end i) we will utilize immuno-biochemical approaches to determine the localization and function of the PSII associated factor Psb27. Additionally, we will use in planta tagged Psb27 lines in order to identify interacting proteins. ii) We will investigate the kinetics of PSII core phosphorylation in relation to the altered functionality of PSII supercomplexes. With fluorometrical and spectroscopical methods we will assess concomitant changes in light harvesting, light energy distribution and transfer. To this end we will use mutant lines with altered thylakoid complex phosphorylation in combination with defined light regimes. By this means we will be able to assign physiological functions of differentially phosphorylated PSII supercomplexes. iii) We will investigate the physiological impact of PSII remodeling on the ability to acclimate to different light environments using Arabidopsis lines impaired in assembly or regulation of PSII supercomplexes. These mutants will be subjected to fluctuating light conditions and tested for their photosynthetic performance. The knowledge obtained about PSII supercomplexes and their remodeling will enable us to evaluate the effects of the light environment on plant growth and yield. In the future the productivity of agricultural important plants might benefit from this knowledge.