拟南芥PDP6蛋白参与光系统I生物发生功能的研究

Photosystem I (PSI) is a multisubunit pigment-protein complex located in the photosynthetic membrane which is indispensable for algae and plants to converts solar energy into chemical energy. However, little is known about the precise mechanism of PSI biogenesis. Therefore, we isolated a PSI deficient Arabidopsis mutants pdp6 (photosystem I deficient protein 6) which showed retarded growth and had pale green leaves. Our preliminary results revealed PSI function of the pdp6 mutant was affected, the abundance of the PSI core proteins PsaA and PsaB were reduced to about 30% of the wild type and PDP6 protein was localized to the chloroplast. Nevertheless, the precise step and molecular mechanisms of PDP6 protein specifically involved in the PSI biogenesis remain unknown. In this project，we aim to study the molecular mechanism how PDP6 is involved in PSI biogenesis using molecular biology, genetics, physiological, biochemical, and spectroscopic approaches. Our research will deepen the understanding of the structure and function of PSI.

光系统I（PSI）是位于光合膜上的多亚基的色素蛋白复合物，目前对其生物发生的具体机制还知之甚少。为此，我们通过筛选PSI功能缺陷的拟南芥突变体并研究引起其表型的蛋白的功能，来丰富对PSI生物发生具体过程的认识。其中，突变体pdp6 （photosystem I deficient protein 6）生长缓慢，叶色发黄，光谱学分析表明其光系统I功能受到影响，免疫印迹分析发现其PSI核心蛋白PsaA和PsaB含量只有野生型的30%左右。PDP6前导肽与GFP的融合蛋白瞬时表达实验结果显示PDP6蛋白位于叶绿体，但它具体参与PSI生物发生的哪个过程，以及如何作用的分子机制还不清楚。本项目拟采用分子生物学，遗传学，生理生化以及光谱学等方法研究PDP6蛋白参与PSI生物发生的具体分子机制，为我们深刻认识PSI结构和功能奠定基础。

酪氨酸是光合电子传递体质体醌（Plastoquinone，PQ）的前体物质。前酪氨酸脱氢是合成酪氨酸的关键酶。尽管关于前酪氨酸脱氢酶的生化功能已有所研究，但是这些结论都是建立在体外生化实验基础上，缺乏遗传学证据。拟南芥中存在两个前酪氨酸脱氢酶编码基因（TyrAAT1 和TyrAAT2），PDP6蛋白是由TyrAAT2编码的。本项目用遗传学手段证明，PDP6蛋白缺失的突变体中，PQ含量减少，光系统I和光系统II功能降低。表明PDP6是合成PQ的关键酶，对于光合功能的实现具有重要作用。