Regulation and function of the zeaxanthin epoxidase

玉米黄质环氧化酶（ZE）催化玉米黄质转化为紫黄质。该反应不仅代表了所谓的叶黄素循环的两个反应之一（在光系统II中起重要的光保护作用），而且是类胡萝卜素生物合成的重要步骤，导致新黄素和植物激素脱落酸（ABA）的形成，这参与了植物的发育和胁迫反应。到目前为止，关于(i)一般ZE的调控和生化特性以及（ii） ZE在叶黄素循环和ABA生物合成中的双重功能的调控知之甚少。我们的初步研究表明，两种不同的ZE亚型在植物中具有活性，它们可能在叶黄素循环活性和ABA生物合成方面具有不同的功能。计划工作的目标是了解ZE在能量耗散和ABA生物合成中的双重功能的调控和功能。为此，将采用两种方法：研究了ZE在拟南芥中两种异构体的过表达和特征，以了解ZE在叶黄素循环和ABA生物合成中的双重作用。2. 从具有不同底物特异性和调节特性的硅藻中异源过表达ZE，以了解ZE的生化特性，特别是关于能量耗散的特性。

The zeaxanthin epoxidase (ZE) catalyzes the conversion of zeaxanthin to violaxanthin. This reaction represents not only one of the two reactions of the so-called xanthophyll cycle (which serves essential photoprotective functions in photosystem II) but is furthermore an important step of carotenoid biosynthesis leading to the formation of neoxanthin and the phytohormone abscisic acid (ABA), which is involved in plant development and stress responses. So far, little is known about (i) the regulation and biochemical properties of the ZE in general and (ii) the regulation of the dual function of the ZE in the xanthophyll cycle and ABA biosynthesis. Our preliminary work indicated that two different isoforms of the ZE are active in plants, which may serve different functions with respect to xanthophyll cycle activity and ABA biosynthesis. The goal of the planned work is to understand the regulation and function of the ZE in relation to its dual function in energy dissipation and ABA biosynthesis. For this purpose, two approaches will be followed: 1. Over-expression and characterisation of the two isoforms of the ZE in Arabidopsis, to understand the dual role of the ZE in the xanthophyll cycle and ABA biosynthesis. 2. The heterologous over-expression of the ZE from diatoms with different substrate specificities and regulation properties, to understand the biochemical properties of the ZE, particularly with respect to energy dissipation.