Regulation of zeaxanthin epoxidation

点击翻译按钮获取中文摘要

The light-induced formation of reactive oxygen species (ROS) is an extremely harmful stress factor for photosynthetic organisms. Higher plants have developed a number of strategies to avoid or minimize damage related to such photo-oxidative stress. The carotenoid zeaxanthin (Zx), which is formed from violaxanthin (Vx) in the de-epoxidation reactions of the so-called xanthophyll cycle, plays a central role in different photoprotective mechanisms in chloroplasts. Zx has not only essential functions in the thermal dissipation of excess light energy in photosystem II (PSII) but also contributes to the deactivation of ROS in the thylakoid membrane. The Zx content in the thylakoid membrane has to be regulated very carefully to avoid undesirable annihilation of absorbed light energy at non-saturating light intensities on the one hand and to allow rapid activation of protective mechanisms under stress conditions on the other hand. The regulation of the activity of the Zx epoxidase - which reconverts Zx to Vx under non-saturating light conditions - is central to these regulatory processes. The goal of this project is to characterize the regulation of the Zx epoxidase and the biochemical properties of this enzyme.