Abstract
Under drought in the presence of strong light, which is potentially induces photoinhibition, absorption of excess light energy causes over-reduction of electron transport chain in chloroplasts. To investigate the regulation of electron transport under such stress condition, we performed proteomic analysis of thylakoid membrane in drought-resistant wild watermelon. We found that new spots with more acidic pI for the Rieske protein, a component of the cyt b6f complex, emerged in response to the stress. These new spots were disappeared by relieving the stress. The in vivo and in vitro analyses suggested that the cyt b6f complex was the major rate-limiting step in the electron transport under stress conditions. We discuss on the possible involvement of the Rieske protein with more acidic pI in the regulation of photosynthetic electron transport activity to avoid photoinhibition of PS I under stress conditions.
