Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, I-37134, Verona, Italy.
Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, via Pascoli 70/3, 20133, Milano, Italy.
Sci Rep. 2017 Sep 11;7(1):11158. doi: 10.1038/s41598-017-11101-7.
Light harvesting for oxygenic photosynthesis is regulated to prevent the formation of harmful photoproducts by activation of photoprotective mechanisms safely dissipating the energy absorbed in excess. Lumen acidification is the trigger for the formation of quenching states in pigment binding complexes. With the aim to uncover the photoprotective functional states responsible for excess energy dissipation in green algae and mosses, we compared the fluorescence dynamic properties of the light-harvesting complex stress-related (LHCSR1) protein, which is essential for fast and reversible regulation of light use efficiency in lower plants, as compared to the major LHCII antenna protein, which mainly fulfills light harvesting function. Both LHCII and LHCSR1 had a chlorophyll fluorescence yield and lifetime strongly dependent on detergent concentration but the transition from long- to short-living states was far more complete and fast in the latter. Low pH and zeaxanthin binding enhanced the relative amplitude of quenched states in LHCSR1, which were characterized by the presence of 80 ps fluorescence decay components with a red-shifted emission spectrum. We suggest that energy dissipation occurs in the chloroplast by the activation of 80 ps quenching sites in LHCSR1 which spill over excitons from the photosystem II antenna system.
用于产氧光合作用的光捕获受到调控，以通过激活光保护机制来防止有害光产物的形成，从而安全地耗散多余吸收的能量。腔室酸化是在色素结合复合物中形成猝灭态的触发因素。为了揭示在绿藻和苔藓中负责多余能量耗散的光保护功能状态，我们比较了光捕获复合物应激相关（LHCSR1）蛋白的荧光动态特性，该蛋白对于快速和可逆地调节低等植物的光利用效率至关重要，而主要的 LHCII 天线蛋白主要起光捕获作用。与 LHCII 相比，LHCSR1 的叶绿素荧光产率和寿命强烈依赖于去污剂浓度，但后者从长寿命态到短寿命态的转变要快得多。低 pH 值和玉米黄质结合增强了 LHCSR1 中猝灭态的相对幅度，其特征是存在具有红移发射光谱的 80 ps 荧光衰减组分。我们认为，通过激活 LHCSR1 中的 80 ps 猝灭位点，可以在叶绿体中耗散能量，这些猝灭位点会将来自光系统 II 天线系统的激子溢出。
