School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, Fogg Building, London E1 4NS, UK.
1] Department of Theoretical Physics, Faculty of Physics, Vilnius University, Saulėtekio Avenue 9, LT-10222 Vilnius, Lithuania [2] Institute of Physics, Center for Physical Sciences and Technology, A. Gostauto 11, LT-01108 Vilnius, Lithuania.
Nat Commun. 2014 Jul 11;5:4433. doi: 10.1038/ncomms5433.
The light-harvesting antenna of higher plant photosystem II has an intrinsic capability for self-defence against intense sunlight. The thermal dissipation of excess energy can be measured as the non-photochemical quenching of chlorophyll fluorescence. It has recently been proposed that the transition between the light-harvesting and self-defensive modes is associated with a reorganization of light-harvesting complexes. Here we show that despite structural changes, the photosystem II cross-section does not decrease. Our study reveals that the efficiency of energy trapping by the non-photochemical quencher(s) is lower than the efficiency of energy capture by the reaction centres. Consequently, the photoprotective mechanism works effectively for closed rather than open centres. This type of defence preserves the exceptional efficiency of electron transport in a broad range of light intensities, simultaneously ensuring high photosynthetic productivity and, under hazardous light conditions, sufficient photoprotection for both the reaction centre and the light-harvesting pigments of the antenna.
高等植物光合作用系统 II 的光捕获天线具有内在的自我防御强光的能力。过量能量的热耗散可以通过叶绿素荧光的非光化学猝灭来测量。最近有人提出，光捕获和自我防御模式之间的转变与光捕获复合物的重组有关。在这里，我们表明，尽管结构发生了变化，但光合作用系统 II 的横截面并没有减少。我们的研究表明，非光化学猝灭剂的能量捕获效率低于反应中心的能量捕获效率。因此，这种光保护机制在关闭而不是打开中心时能有效地发挥作用。这种防御方式在广泛的光强范围内保持了电子传递的异常效率，同时确保了高光合作用生产力，并且在危险的光照条件下，为反应中心和天线的光捕获色素提供了足够的光保护。
