Regulation of zeaxanthin epoxidation

光诱导的活性氧（ROS）的形成是光合生物极其有害的应激因子。高等植物已经发展出许多策略来避免或减少与这种光氧化应激有关的损害。类胡萝卜素玉米黄质（Zx）是由紫黄质（Vx）在所谓的叶黄素循环的去环氧化反应中形成的，在叶绿体的不同光保护机制中起着核心作用。Zx不仅在光系统II （PSII）中多余光能的热耗散中起重要作用，而且还有助于类囊体膜中ROS的失活。必须非常仔细地调节类囊体膜中的Zx含量，以避免在非饱和光强度下吸收光能的不良湮灭，并在另一方面允许在应力条件下快速激活保护机制。Zx环氧化酶的活性调控——在不饱和光条件下将Zx重新转化为Vx——是这些调控过程的核心。本项目的目的是表征Zx环氧化酶的调控和该酶的生化特性。

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.