Non-photochemical quenching of photosystem i as an adaptive response to prolonged drought

Abstract

Excess excitation energy (EEE) dissipation in photosystem II (PSII) is well established, while it is less studied and documented for PSI. Using Jatropha curcas, a semi-evergreen, tropical, non-edible oil-seed-bearing shrub, Sapeta et al. (2023) provide evidence for the significance of energy quenching in PSI under prolonged drought. Jatropha curcas receives considerable attention for sustainable (green) manufacturing of biodiesel and is recognized for its high tolerance to drought, capable of arresting growth while maintaining steady shoot water content and green leaves after several weeks of water withdrawal. In search for the molecular grounds for the drought tolerance of J. curcas, the study addresses the pigment and protein composition of PSI and PSII, and the thermal dissipation mechanisms of EEE absorbed by the light-harvesting complex (LHCI and LHCII) antennae of PSI and PSII. Their biochemical and spectroscopic measurements let them conclude that thermal energy dissipation by non-photochemical quenching (NPQ) indeed exists in PSI-LHCI and is essential for minimizing PSI inactivation and securing survival of J. curcas under prolonged drought stress. The photoprotection of PSI-LHCI by NPQ, together with the NPQ of PSII-LHCII and the prompt protein recovery of the PSII core complex, permit J. curcas plants to restart leaf CO2 assimilation and growth shortly after soil re-watering and stomatal re-opening.