Institute of Low-Temperature Science, Hokkaido University, N19 W8 Kita-ku, Sapporo, 060-0819, Japan.
Faculty of Science, Hokkaido University, N10 W8 Kita-ku, Sapporo, 060-0810, Japan.
J Plant Res. 2019 Nov;132(6):867-880. doi: 10.1007/s10265-019-01138-2. Epub 2019 Sep 20.
Mosses are one of the earliest land plants that diverged from fresh-water green algae. They are considered to have acquired a higher capacity for thermal energy dissipation to cope with dynamically changing solar irradiance by utilizing both the "algal-type" light-harvesting complex stress-related (LHCSR)-dependent and the "plant-type" PsbS-dependent mechanisms. It is hypothesized that the formation of photosystem (PS) I and II megacomplex is another mechanism to protect photosynthetic machinery from strong irradiance. Herein, we describe the analysis of the PSI-PSII megacomplex from the model moss, Physcomitrella patens, which was resolved using large-pore clear-native polyacrylamide gel electrophoresis (lpCN-PAGE). The similarity in the migration distance of the Physcomitrella PSI-PSII megacomplex to the Arabidopsis megacomplex shown during lpCN-PAGE suggested that the Physcomitrella PSI-PSII and Arabidopsis megacomplexes have similar structures. Time-resolved chlorophyll fluorescence measurements show that excitation energy was rapidly and efficiently transferred from PSII to PSI, providing evidence of an ordered association of the two photosystems. We also found that LHCSR and PsbS co-migrated with the Physcomitrella PSI-PSII megacomplex. The megacomplex showed pH-dependent chlorophyll fluorescence quenching, which may have been induced by LHCSR and/or PsbS proteins with the collaboration of zeaxanthin. We discuss the mechanism that regulates the energy distribution balance between two photosystems in Physcomitrella.
藓类植物是最早从淡水绿藻中分化出来的陆地植物之一。它们被认为通过利用“藻类型”光捕获复合体应激相关（LHCSR）依赖性和“植物型”PsbS 依赖性机制，获得了更高的热能耗散能力，以应对动态变化的太阳辐照度。有人假设，光系统（PS）I 和 II 巨复合物的形成是另一种保护光合机制免受强辐照度的机制。在此，我们描述了使用大孔径透明天然聚丙烯酰胺凝胶电泳（lpCN-PAGE）对模式藓类植物，Physcomitrella patens 的 PSI-PSII 巨复合物的分析。lpCN-PAGE 中 Physcomitrella PSI-PSII 巨复合物与拟南芥巨复合物的迁移距离相似表明，Physcomitrella PSI-PSII 和拟南芥巨复合物具有相似的结构。时间分辨叶绿素荧光测量表明，激发能从 PSII 迅速有效地转移到 PSI，为两个光系统的有序缔合提供了证据。我们还发现 LHCSR 和 PsbS 与 Physcomitrella PSI-PSII 巨复合物共迁移。巨复合物表现出 pH 依赖性叶绿素荧光猝灭，这可能是由 LHCSR 和/或 PsbS 蛋白与玉米黄质的协同作用引起的。我们讨论了在 Physcomitrella 中调节两个光系统之间能量分布平衡的机制。
