Jahns Peter, Holzwarth Alfred R
Plant Biochemistry, Heinrich-Heine-University Düsseldorf, Universitätsstr.1, D-40225 Düsseldorf, Germany.
Biochim Biophys Acta. 2012 Jan;1817(1):182-93. doi: 10.1016/j.bbabio.2011.04.012. Epub 2011 May 1.
Photoprotection of photosystem II (PSII) is essential to avoid the light-induced damage of the photosynthetic apparatus due to the formation of reactive oxygen species (=photo-oxidative stress) under excess light. Carotenoids are known to play a crucial role in these processes based on their property to deactivate triplet chlorophyll (³Chl*) and singlet oxygen (¹O₂*). Xanthophylls are further assumed to be involved either directly or indirectly in the non-photochemical quenching (NPQ) of excess light energy in the antenna of PSII. This review gives an overview on recent progress in the understanding of the photoprotective role of the xanthophylls zeaxanthin (which is formed in the light in the so-called xanthophyll cycle) and lutein with emphasis on the NPQ processes associated with PSII of higher plants. The current knowledge supports the view that the photoprotective role of Lut is predominantly restricted to its function in the deactivation of ³Chl*, while zeaxanthin is the major player in the deactivation of excited singlet Chl (¹Chl*) and thus in NPQ (non-photochemical quenching). Additionally, zeaxanthin serves important functions as an antioxidant in the lipid phase of the membrane and is likely to act as a key component in the memory of the chloroplast with respect to preceding photo-oxidative stress. This article is part of a Special Issue entitled: Photosystem II.
光系统II（PSII）的光保护对于避免光合机构因在过量光照下形成活性氧（即光氧化应激）而受到光诱导损伤至关重要。基于类胡萝卜素使三线态叶绿素（³Chl*）和单线态氧（¹O₂*）失活的特性，已知其在这些过程中起着关键作用。叶黄素被进一步认为直接或间接参与了PSII天线中过量光能的非光化学猝灭（NPQ）。本文综述了对叶黄素玉米黄质（在光下通过所谓的叶黄素循环形成）和叶黄素光保护作用理解的最新进展，重点关注与高等植物PSII相关的NPQ过程。目前的知识支持这样一种观点，即叶黄素（Lut）的光保护作用主要限于其使³Chl失活的功能，而玉米黄质是激发单线态叶绿素（¹Chl）失活从而在NPQ（非光化学猝灭）中起主要作用的物质。此外，玉米黄质在膜的脂质相中作为抗氧化剂发挥重要功能，并且可能在叶绿体对先前光氧化应激的记忆中充当关键成分。本文是名为：光系统II的特刊的一部分。
