Preferential Decay of the CF₁-ε Subunit Induces Thylakoid Uncoupling in Wild Watermelon Under Drought Stress

Abstract

Photosynthetic energy conversion in plants involves the formation of a proton gradient across thylakoid membranes, but the mechanisms for balancing the membrane potential have been poorly elucidated. We found that drought stress induces selective decomposition of the ε subunit in the CF_oCF₁ ATP synthase. Thylakoid membranes from stressed leaves showed reduced efficiencies for proton gradient formation and energy coupling, but addition of the recombinant ε subunit significantly suppressed their “leaky” property. We conclude that the selective decomposition of the e subunit induces partial uncoupling of thylakoid membranes under drought, and hence contributes to the avoidance of over-acidification in the thylakoid lumen under excess light conditions.