"Photosynthesis is one of the most important biological processes on Earth. Photosystem I and Photosystem II are the key protein complexes in the photosynthetic or thylakoid membrane of chloroplasts for converting light energy. They mediate light-driven electron transport through the thylakoid membrane with help of additional light harvesting proteins. Both Photosystem I and II are organized into large supercomplexes with variable numbers of specifically attached membrane-bound light harvesting proteins. Under varying natural conditions plants have to regulate light harvesting to keep maximum efficiency of photosynthetic reactions under light limiting conditions and to prevent the photosynthetic apparatus from photooxidative damage under high light conditions. Acclimation and protective mechanisms involve considerable structural changes at the level of both individual photosynthetic proteins and the entire photosynthetic membrane, which are largely unexplored. Increasing our knowledge of stress induced structural changes of the photosynthetic apparatus is important for overall understanding of regulatory mechanisms of photosynthetic performance. Such information is of great importance to e.g. a booming field of artificial photosynthesis, which tries to mimic photosynthetic reactions at the laboratory conditions. The aim of proposed project is to monitor stress-induced structural changes (different light conditions, elevated temperature) of the plant photosynthetic apparatus at the level of individual supercomplexes of Photosystem I and Photosystem II and their associated antenna complexes using transmission electron microscopy and single particle image analysis. Another challenging aim of the research proposal is a visualization of stress-induced structural changes of (i) the overall organization and distribution of individual photosynthetic proteins within the thylakoid membrane and (ii) a folding of entire thylakoid membrane using cryo electron tomography."