The xanthophyll cycle pool size controls the kinetics of non-photochemical quenching in Arabidopsis thaliana.

Arabidopsis plants overexpressing beta-carotene hydroxylase 1 accumulate over double the amount of zeaxanthin present in wild-type plants. The final amplitude of non-photochemical quenching (NPQ) was found to be the same in these plants, but the kinetics were different. The formation and relaxation of NPQ consistently correlated with the de-epoxidation state of the xanthophyll cycle pool and not the amount of zeaxanthin. These data indicate that zeaxanthin and violaxanthin antagonistically regulate the switch between the light harvesting and photoprotective modes of the light harvesting system and show that control of the xanthophyll cycle pool size is necessary to optimize the kinetics of NPQ.