Changes in Molecular Organization of Thylakoid Membranes during the Cell Cycle of Scenedesmus obliquus

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Cultures of Scenedesmus obliquus, synchronized by a light-dark regime of 14 : 10 hours, show distinct changes in their photosynthetic activity with a maximum at the 8th h and a minimum at the 16th h after onset of illumination. The activity differences occur under limiting light-intensities as well as under saturating light-intensities, indicating at least two different factors regulating photosynthesis during the cell cycle. Based on differences in the ratio of oligomeric to monomeric pigment-protein complexes between 8 and 16 h old cells, and Mg^<2+>-induced effects on the fluorescence properties of chloroplast particles deriving from 8 and 16 h old cells, changes in the molecular organization of the photosynthetic apparatus are documented. These changes might regulate energy distribution within the photosynthetic apparatus during ontogenetic development and are supposed to be responsible for the differences in activity under limiting light-intensities. By analysis of pure PS II-particles from cells with maximal and minimal photosynthetic activity it could be demonstrated that changes occurring in PS II proper account for the differences in photosynthetic capacity measured under saturing light. A model demonstrating the changes in the molecular organization of thylakoid membranes occurring during ontogenetic development of Scenedesmus obliquus is presented.
日本植物生理学会の論文