Bassi R, Caffarri S
Dipartimento Scientifico e Tecnologico, Università di Verona, Strada Le Grazie 15, 37134, Verona, Italy,
Photosynth Res. 2000;64(2-3):243-56. doi: 10.1023/A:1006409506272.
Photoprotection of the chloroplast is an important component of abiotic stress resistance in plants. Carotenoids have a central role in photoprotection. We review here the recent evidence, derived mainly from in vitro reconstitution of recombinant Lhc proteins with different carotenoids and from carotenoid biosynthesis mutants, for the existence of different mechanisms of photoprotection and regulation based on xanthophyll binding to Lhc proteins into multiple sites and the exchange of chromophores between different Lhc proteins during exposure of plants to high light stress and the operation of the xanthophyll cycle. The use of recombinant Lhc proteins has revealed up to four binding sites in members of Lhc families with distinct selectivity for xanthophyll species which are here hypothesised to have different functions. Site L1 is selective for lutein and is here proposed to be essential for catalysing the protection from singlet oxygen by quenching chlorophyll triplets. Site L2 and N1 are here proposed to act as allosteric sites involved in the regulation of chlorophyll singlet excited states by exchanging ligand during the operation of the xanthophyll cycle. Site V1 of the major antenna complex LHC II is here hypothesised to be a deposit for readily available substrate for violaxanthin de-epoxidase rather than a light harvesting pigment. Moreover, xanthophylls bound to Lhc proteins can be released into the lipid bilayer where they contribute to the scavenging of reactive oxygen species produced in excess light.
叶绿体的光保护是植物抗非生物胁迫的重要组成部分。类胡萝卜素在光保护中起着核心作用。我们在此综述近期的证据,这些证据主要来自于用不同类胡萝卜素对重组Lhc蛋白进行体外重构以及类胡萝卜素生物合成突变体的研究,表明基于叶黄素与Lhc蛋白结合到多个位点以及在植物暴露于高光胁迫期间不同Lhc蛋白之间发色团的交换和叶黄素循环的运行,存在不同的光保护和调节机制。重组Lhc蛋白的使用揭示了Lhc家族成员中多达四个结合位点,这些位点对叶黄素种类具有不同的选择性,在此假设它们具有不同的功能。位点L1对叶黄素具有选择性,在此提出其对于通过淬灭叶绿素三线态来催化对单线态氧的保护至关重要。位点L2和N1在此提出作为变构位点,在叶黄素循环运行期间通过交换配体参与叶绿素单重激发态的调节。主要天线复合体LHC II的位点V1在此假设是紫黄质脱环氧化酶现成底物的储存位点,而不是光捕获色素。此外,与Lhc蛋白结合的叶黄素可以释放到脂质双层中,在那里它们有助于清除过量光照产生的活性氧。