An irradiation density dependent energy relaxation in plant photosystem II antenna assembly.
An irradiation density dependent energy relaxation in plant photosystem II antenna assembly.
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DOI：
10.1016/j.bbabio.2014.11.010
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发表时间：
2015-02
期刊：
影响因子：
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通讯作者：
Wenming Tian;Jun Chen;Liezheng Deng;Mingdong Yao;Heping Yang;Yang Zheng;Rongrong Cui;G. Sha
中科院分区：
文献类型：
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作者：
Wenming Tian;Jun Chen;Liezheng Deng;Mingdong Yao;Heping Yang;Yang Zheng;Rongrong Cui;G. Sha
植物光系统II （PSII）是一种多组分的色素蛋白复合物，通过色素的光激发收集阳光，并将光能转化为化学能。针对强光诱导的光损伤，天线色素的过量光吸收触发了植物PSII的光保护机制。非光化学能松弛作为一种主要的光保护方式，本质上与过量光吸收有关。本研究通过对颗粒膜（BBY）、PSII反应中心功能片段和分离的集光复合物LHCII进行稳态和瞬态叶绿素荧光测量，研究了在不同入射光密度下植物PSII复合物的能量松弛。基于这些样品的叶绿素荧光衰减，发现当辐照增加到一定的密度水平时，LHCII组件，特别是颗粒膜中PSII超配合物的天线组件发生辐照密度依赖的能量松弛。相应地，随着辐照密度从6.1 × 109光子cm−2脉冲−1增加到5.5 × 1010光子cm−2脉冲−1，高度分离的BBY片段的平均叶绿素荧光寿命从~ 1680 ps逐渐减小到~ 1360 ps。荧光衰减变化与lhcii聚集程度的关系分析表明，三聚体lhcii的密集排列可能是这种辐照密度依赖性能量弛豫发生的结构基础。一旦改变辐照密度，这种能量松弛是快速可逆的，这意味着它可能在植物PSII的光保护中起重要作用。
Plant photosystem II (PSII) is a multicomponent pigment-protein complex that harvests sunlight via pigments photoexcitation, and converts light energy into chemical energy. Against high light induced photodamage, excess light absorption of antenna pigments triggers the operation of photoprotection mechanism in plant PSII. Non-photochemical energy relaxation as a major photoprotection way is essentially correlated to the excess light absorption. Here we investigate the energy relaxation of plant PSII complexes with varying incident light density, by performing steady-state and transient chlorophyll fluorescence measurements of the grana membranes (called as BBY), functional moiety PSII reaction center and isolated light-harvesting complex LHCII under excess light irradiation. Based on the chlorophyll fluorescence decays of these samples, it is found that an irradiation density dependent energy relaxation occurs in the LHCII assemblies, especially in the antenna assembly of PSII supercomplexes in grana membrane, when irradiation increases to somewhat higher density levels. Correspondingly, the average chlorophyll fluorescence lifetime of the highly isolated BBY fragments gradually decreases from ~ 1680 to ~ 1360 ps with increasing the irradiation density from 6.1 × 109to 5.5 × 1010photon cm− 2pulse− 1. Analysis of the relation of fluorescence decay change to the aggregation extent of LHCIIs suggests that a dense arrangement of trimeric LHCIIs is likely the structural base for the occurrence of this irradiation density dependent energy relaxation. Once altering the irradiation density, this energy relaxation is quickly reversible, implying that it may play an important role in photoprotection of plant PSII.