Photosynthetic Adaptation to High Temperature Associated with Thylakoid Membranes of <italic>Synechococcus</italic> PCC7002

Abstract

Photosynthetic adaptation to high temperature was investigated in intact cells and isolated thylakoid membranes of the cyanobacterium, Synechococcus PCC7002. In intact cells, the thermal stability of photosynthesis and photosystem 2-mediated electron transport from H2O to 1,4-benzoquinone changed in concert with growth temperature. The photosystem 2-mediated electron transport from H2O to phenyl-1,4-benzoquinone showed greater thermal stability in thylakoid membranes isolated from cells which had adapted to high temperature than in those from non-adapted cells. Enhanced thermal stability was also observed in the thylakoid membranes in the transport of electrons from H2O to 2,6-dichlorophenolindophenol but not in the transport of electrons from diphenylcarbazide to 2,6-dichlorophenolindophenol. These observations suggest that oxygen-evolving sites acquire enhanced thermal stability, and that factors which are responsible for thermal stability remain in isolated thylakoid membranes.