高等植物围绕光系统I（PSI）的环式电子传递在平衡ATP/NADPH比例和植物光保护中发挥重要功能，其中NADH脱氢酶（NDH）参与的环式电子传递是一条很重要的途径。尽管NDH-PSI复合物早在十几年前就已被鉴定出来，但结构研究进展却十分缓慢。目前已有的低分辨率结构可以大体区分NDH和PSI的组装位置，但复合物的精细结构和发挥功能的分子机制尚不明确。本项目拟以高等植物NDH-PSI复合物为研究对象，综合运用单颗粒电子显微镜技术和蛋白质晶体学方法，解析其高分辨率的三维结构，揭示NDH-PSI的组装方式及各个亚基的精细结构和相互作用。在结构的基础上，我们将开展相应的功能研究，最终结合结构和功能数据，阐明NDH-PSI环式电子传递的分子机理，揭示其在植物光保护和应对胁迫环境的作用机制。本项目的实施，预期将为揭示光合作用的分子机理提供结构基础，并为光合作用相关的应用研究提供依据。

Cyclic electron transport (CET) around photosystem I (PSI) plays an important role in balancing the ATP/NADPH ratio and the photoprotection of the plants. The NAD(P)H dehydrogenase complex (NDH) has a key function in one of the CET pathways. .Although the NDH-PSI supercomplex has been identified in a decade ago, but the structure studies are rather slowly. Up to now, only the negative stained single particle electron microscopy analysis can be obtained in a rather low resolution. This structure revealed the supercomplex contained two copies of PSI attached to one NDH complex. However, the detailed structure of this supercomplex, and its molecular mechanism are still unclear. This project intends to purify NDH-PSI supercomplex from higher plant, and using single-particle electron microscopy, in combined with the X-ray crystallography method to solve its three-dimensional structure in high resoltion. The reults will reveal the detailed strutures of each subunit in the NDH-PSI supercomplex and their interactions.On the basis of structure, we will carry out the corresponding functional research, and finally combine the structure and function to elucidate the molecular mechanism of NDH-PSI supercompex involved in cyclic electron transport. The results will provide solid basis for revealing the mechanism of plant photoprotection and coping with stress environment. The implementation of this project is expected to provide a basis for comprehensive analysis of the structure of photosynthesis-related membrane protein complexes, and provide an important theoretical basis for the relevant applied research based on photosynthesis mechanism research.