Regulation of zeaxanthin epoxidation

光诱导产生的活性氧(ROS)是一种对光合作用生物极为有害的胁迫因子。高等植物已经制定了许多策略来避免或最大限度地减少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)在叶黄素循环的去环氧化反应中形成的，在叶绿体不同的光保护机制中起着核心作用。ZX不仅在光系统II(PSII)过剩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。类囊体膜中的ZX含量必须非常仔细地调节，一方面避免在非饱和光强下吸收的光能被不受欢迎的湮灭，另一方面允许在胁迫条件下快速激活保护机制。对ZX环氧合酶活性的调节--在非饱和光照条件下将ZX重新转化为VX--是这些调节过程的核心。本项目的目标是表征ZX环氧酶的调节和该酶的生化性质。

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.