Spatiotemporal organization of thylakoid membrane biogenesis in cyanobacteria

大多数光自养细菌都含有一种名为类囊体的复杂的细胞膜系统。这些内部结构代表了介导光合作用电子流和随后的三磷酸腺苷生成的能量传导膜。越来越多的证据表明，这种生物能量机制的生物发生和结构动力学在空间和时间上都是高度有序的。我们最近的发现表明，在蓝藻聚胞藻6803的模型中，光系统II(PSII)的生物发生始于类囊体融合形成会聚小管的区域。由于其突触样的外观，这些细胞偶尔会在被称为“甲状突触”的部位与质膜接触。这些生物膜亚结构域的建立需要膜成形因子CURT和ANCM。Curt在严重弯曲的相互连接的小管上积累到高水平，这些小管来自横跨整个细胞外围的生物膜网络。相比之下，ANCM仅定位于肾小管系统的不同部位，并标记甲状旁腺区域。因此，这两者都是聚囊藻6803类囊体膜生物发生的亚细胞组织的真正标志。本项目综合运用遗传学、生物化学和各种微观方法，旨在阐明PSII生物发生的时空组织过程中这些内部膜亚域的工作模式。基于对Curt和ANCM以及与PSII相关的几个生物发生因子的鉴定，需要解决的中心问题是：(I)是什么决定了生物起源区域的结构动力学？(2)它们的确切职能组织是什么？

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?