State Key Laboratory of Microbial Technology, and Marine Biotechnology Research Center, Shandong University, Qingdao 266237, China.
Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
Plant Physiol. 2022 Oct 27;190(3):1883-1895. doi: 10.1093/plphys/kiac372.
Efficient solar energy conversion is ensured by the organization, physical association, and physiological coordination of various protein complexes in photosynthetic membranes. Here, we visualize the native architecture and interactions of photosynthetic complexes within the thylakoid membranes from a fast-growing cyanobacterium Synechococcus elongatus UTEX 2973 (Syn2973) using high-resolution atomic force microscopy. In the Syn2973 thylakoid membranes, both photosystem I (PSI)-enriched domains and crystalline photosystem II (PSII) dimer arrays were observed, providing favorable membrane environments for photosynthetic electron transport. The high light (HL)-adapted thylakoid membranes accommodated a large amount of PSI complexes, without the incorporation of iron-stress-induced protein A (IsiA) assemblies and formation of IsiA-PSI supercomplexes. In the iron deficiency (Fe-)-treated thylakoid membranes, in contrast, IsiA proteins densely associated with PSI, forming the IsiA-PSI supercomplexes with varying assembly structures. Moreover, type-I NADH dehydrogenase-like complexes (NDH-1) were upregulated under the HL and Fe- conditions and established close association with PSI complexes to facilitate cyclic electron transport. Our study provides insight into the structural heterogeneity and plasticity of the photosynthetic apparatus in the context of their native membranes in Syn2973 under environmental stress. Advanced understanding of the photosynthetic membrane organization and adaptation will provide a framework for uncovering the molecular mechanisms of efficient light harvesting and energy conversion.
光合作用膜中各种蛋白质复合物的组织、物理关联和生理协调确保了高效的太阳能转化。在这里，我们使用高分辨率原子力显微镜可视化了来自快速生长的蓝藻集胞藻 UTEX 2973（Syn2973）的类囊体膜中光合作用复合物的天然结构和相互作用。在 Syn2973 类囊体膜中，观察到富含光系统 I（PSI）的区域和结晶光系统 II（PSII）二聚体阵列，为光合作用电子传递提供了有利的膜环境。高光（HL）适应的类囊体膜容纳了大量的 PSI 复合物，而没有铁胁迫诱导蛋白 A（IsiA）组装体的掺入和 IsiA-PSI 超复合物的形成。相比之下，在缺铁（Fe-）处理的类囊体膜中，IsiA 蛋白与 PSI 紧密结合，形成具有不同组装结构的 IsiA-PSI 超复合物。此外，在 HL 和 Fe-条件下，I 型 NADH 脱氢酶样复合物（NDH-1）上调，并与 PSI 复合物建立密切联系，以促进循环电子传递。我们的研究提供了在 Syn2973 中，在其天然膜的背景下，环境胁迫下光合作用装置的结构异质性和可塑性的深入了解。对光合作用膜组织和适应的深入理解将为揭示高效光捕获和能量转换的分子机制提供框架。
