Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
Sci Rep. 2017 Apr 7;7:46100. doi: 10.1038/srep46100.
Glaucophytes are primary symbiotic algae with unique plastids called cyanelles, whose structure is most similar to ancestral cyanobacteria among plastids in photosynthetic organisms. Here we compare the regulation of photosynthesis in glaucophyte with that in cyanobacteria in the aim of elucidating the changes caused by the symbiosis in the interaction between photosynthetic electron transfer and other metabolic pathways. Chlorophyll fluorescence measurements of the glaucophyte Cyanophora paradoxa NIES-547 indicated that plastoquinone (PQ) pool in photosynthetic electron transfer was reduced in the dark by chlororespiration. The levels of nonphotochemical quenching of chlorophyll fluorescence was high in the dark but decreased under low light, and increased again under high light. This type of concave light dependence was quite similar to that observed in cyanobacteria. Moreover, the addition of ionophore hardly affected nonphotochemical quenching, suggesting state transition as a main component of the regulatory system in C. paradoxa. These results suggest that cyanelles of C. paradoxa retain many of the characteristics observed in their ancestral cyanobacteria. From the viewpoint of metabolic interactions, C. paradoxa is the primary symbiotic algae most similar to cyanobacteria than other lineages of photosynthetic organisms.
蓝藻是具有独特质体的主要共生藻类，称为蓝细菌，其结构与光合生物质体中原始蓝细菌最相似。在这里，我们比较了蓝藻和蓝细菌光合作用的调控，旨在阐明共生作用引起的光合作用电子传递和其他代谢途径相互作用的变化。蓝藻 Cyanophora paradoxa NIES-547 的叶绿素荧光测量表明，在黑暗中，质体醌 (PQ) 池通过光呼吸还原。在黑暗中，叶绿素荧光的非光化学猝灭水平较高，但在低光下降低，在高光下再次升高。这种凹形光依赖性与在蓝细菌中观察到的非常相似。此外，添加离质体几乎不影响非光化学猝灭，表明状态转换是 C. paradoxa 调控系统的主要组成部分。这些结果表明，C. paradoxa 的蓝细菌质体保留了其原始蓝细菌中观察到的许多特征。从代谢相互作用的角度来看，C. paradoxa 是与蓝细菌最相似的主要共生藻类，而不是其他光合生物谱系。
