Correlation between changes in light energy distribution and changes in thylakoid membrane polypeptide phosphorylation in Chlamydomonas reinhardtii.

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Abstract
A new method was used to extensively modify the redox state of the plastoquinone pool in C. reinhardtii intact cells. This was achieved by an anaerobic treatment that inhibits the chlororespiratory pathway recently described by Bennoun (1982). A state I (plus 3,4-dichlorophenyl-1,1,-dimethylurea) .fwdarw. anaerobic state transition induced a decrease in the maximal fluorescence yield at room temperature and in the FPSII/FPSI [photosystem II fluoresence/photosystem I fluorescence] ratio at 77.degree. K; this was 3 times larger than in a classical state I .fwdarw. state II transition. The fluorescence changes observed in vivo were similar in amplitude to those observed in vitro upon transfer to the light of dark-adapted, broken chloroplasts incubated in the presence of ATP. The phosphorylation pattern of thylakoid polypeptides in C. reinhardtii was compared in vitro and in vivo using .gamma.-[32P]ATP and [32P]orthophosphate labeling, respectively. The same set of polypeptides, mainly light-harvesting complex polypeptides, was phosphorylated in both cases. This phosphorylation process is apparently reversible and is mediated by the redox state of the plastoquinone pool in vivo as well as in vitro. Similar changes of even larger amplitude were observed with the F34 mutant intact cells lacking in photosystem II centers. The presence of the photosystem II centers is then not required for the occurrence of the plastoquinone-mediated phosphorylation of light-harvesting complex polypeptides.