Abstract
In higher plants under drought/strong light stress, limited entry of CO2 into the leaf causes the suppression of photosynthetic carbon fixation, and the electron transport chain is prone to be over-reduced, leading to the oxidative damages in photosynthetic apparatus. To elucidate the regulation of photochemistry under such conditions, we analyzed the change in the proteome of the membrane fraction of wild watermelon leaves suffering the stress. Two-dimentional electrophoresis and Western blot revealed that there were multiple spots for the chloroplast Rieske protein, a subunit of the cytochrome b6f complex, with very similar molecular weights but with different isoelectric points. Furthermore, some new spots with more acidic pI appeared under the stress, but disappeared upon resuming irrigation. These results suggested the involvement of post-translational modification of Rieske protein in the regulation of electron transport under excess light stress.
