Spatiotemporal organization of thylakoid membrane biogenesis in cyanobacteria

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Most photoautotrophic bacteria contain a sophisticated intracellular membrane system named thylakoids. These internal structures represent energy transducing membranes that mediate photosynthetic electron flow and subsequent ATP generation. Accumulating evidence suggests that the biogenesis and structural dynamics of this bioenergetic machinery are highly ordered by both spatial and temporal means. Our recent findings indicate that photosystem II (PSII) biogenesis in the model cyanobacterium Synechocystis 6803 is initiated at regions where thylakoids fuse to form convergence tubules. These occasionally contact the plasma membrane at sites named “thylapses” due to their synapse-like appearance. The establishment of these biogenic membrane sub-domains requires the membrane-shaping factors CurT and AncM. CurT accumulates to high levels at heavily bended interconnected tubules which from a biogenic membrane network spanning the periphery of the entire cell. In contrast, AncM localizes only to distinct spots of the tubular system and marks thylapse regions. Thus, both serve as bona fide landmarks for the subcellular organization of thylakoid membrane biogenesis in Synechocystis 6803. By applying a blend of genetic, biochemical, and various microscopic methods this project aims at elucidating the working mode of these internal membrane sub-domains during the spatiotemporal organization of PSII biogenesis. Based on the identification of CurT and AncM as well as several PSII-related biogenesis factors, the central questions to be addressed are: (i) What determines the structural dynamics of biogenic regions? (ii) What is their precise functional organization?