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Title: In vivo quality control of photosystem II in cyanobacteria Synechocystis sp. PCC 6803: D1 protein degradation and repair under the influence of light, heat and darkness
Authors: Singh, Munna
Satoh, Kimiyuki
Yamamoto, Yasusi
Kanervo, Eira
Aro, Eva-Mari
Keywords: D1 degradation;Photoinhibition;Protease;Photosystem II;Synechocystis sp. PCC 6803;Cyanobacteria
Issue Date: Aug-2008
Publisher: CSIR
Abstract: The cells of Synechocystis sp. PCC 6803 were subjected under photoinhibitory irradiation (600 μmolm⁻²s⁻¹) at various temperatures (20-40°C) to study in vivo quality control of photosystem II (PSII). The protease biogenesis and its consequences on photosynthetic efficiency (chlorophyll fluorescence ratio Fv/Fm) of the PSII, D1 degradation and repair were monitored during illumination and darkness. The loss in Fv/Fm value and degradation of D1 protein occurred not only under high light exposure, but also continued when the cells were subjected under dark restoration process after high light exposure. No loss in Fv/Fm value or D1 degradation occurred during recovery under growth/low light (30 μmol m⁻² s⁻¹). Further, it helped the resynthesis of new D1 protein, essential to sustain quality control of PSII. In vivo triggering of D1 protein required high light exposure to switch-on the protease biosynthesis to maintain protease pool which induced temperature-dependent enzymatic proteolysis of photodamaged D1 protein during photoinhition and dark incubation. Our findings suggested the involvement and overexpression of a membrane-bound FtsH protease during high light exposure which caused degradation of D1 protein, strictly regulated by high temperature (30-40ºC). However, lower temperature (20ºC) prevented further loss of photoinhibited PSII efficiency in vivo and also retarded temperature-dependent proteolytic process of D1 degradation.
Page(s): 237-243
ISSN: 0301-1208
Appears in Collections: IJBB Vol.45(4) [August 2008]

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