CESAM-Centre for Environmental and Marine Studies, Department of Biology, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Molecules. 2020 Oct 11;25(20):4617. doi: 10.3390/molecules25204617.
Light is a paramount parameter driving photosynthesis. However, excessive irradiance leads to the formation of reactive oxygen species that cause cell damage and hamper the growth of photosynthetic organisms. Xanthophylls are key pigments involved in the photoprotective response of plants and algae to excessive light. Of particular relevance is the operation of xanthophyll cycles (XC) leading to the formation of de-epoxidized molecules with energy dissipating capacities. Neoxanthin, found in plants and algae in two different isomeric forms, is involved in the light stress response at different levels. This xanthophyll is not directly involved in XCs and the molecular mechanisms behind its photoprotective activity are yet to be fully resolved. This review comprehensively addresses the photoprotective role of 9'--neoxanthin, the most abundant neoxanthin isomer, and one of the major xanthophyll components in plants' photosystems. The light-dependent accumulation of all--neoxanthin in photosynthetic cells was identified exclusively in algae of the order Bryopsidales (Chlorophyta), that lack a functional XC. A putative photoprotective model involving all--neoxanthin is discussed.
光是驱动光合作用的一个重要参数。然而，过高的辐照度会导致活性氧的形成，从而造成细胞损伤，并阻碍光合作用生物的生长。叶黄素是植物和藻类对过量光线的光保护反应中涉及的关键色素。特别相关的是叶黄素循环（XC）的运作，导致具有能量耗散能力的去氧化分子的形成。新黄质存在于植物和藻类中的两种不同的异构形式中，在不同的水平上参与光胁迫反应。这种叶黄素不直接参与 XC，其光保护活性的分子机制尚未完全解决。这篇综述全面介绍了 9'--新黄质的光保护作用，9'--新黄质是最丰富的新黄质异构体之一，也是植物光合作用系统中主要的叶黄素成分之一。在光合作用细胞中，光依赖性的全--新黄质的积累仅在缺乏功能性 XC 的 Bryopsidales 目（绿藻门）的藻类中被发现。讨论了一个涉及全--新黄质的假定光保护模型。
