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胁迫因子。高等植物已经开发了许多策略来避免或最小化与这种光氧化胁迫相关的损害。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脱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）中具有重要的热耗散功能，而且有助于类囊体膜中ROS的失活。必须非常小心地调节类囊体膜中的Zx含量，以一方面避免在非饱和光强度下吸收的光能的不期望的湮灭，另一方面允许在胁迫条件下保护机制的快速激活。Zx环氧酶的活性调节-其在非饱和光条件下将Zx再转化为Vx-是这些调节过程的核心。该项目的目标是表征Zx环氧酶的调节和该酶的生化特性。

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.