School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK.
School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK.
Biochim Biophys Acta Bioenerg. 2018 Sep;1859(9):666-675. doi: 10.1016/j.bbabio.2018.03.005. Epub 2018 Mar 13.
Non-photochemical quenching (NPQ) of chlorophyll fluorescence is the process by which excess light energy is harmlessly dissipated within the photosynthetic membrane. The fastest component of NPQ, known as energy-dependent quenching (qE), occurs within minutes, but the site and mechanism of qE remain of great debate. Here, the chlorophyll fluorescence of Arabidopsis thaliana wild type (WT) plants was compared to mutants lacking all minor antenna complexes (NoM). Upon illumination, NoM exhibits altered chlorophyll fluorescence quenching induction (i.e. from the dark-adapted state) characterised by three different stages: (i) a fast quenching component, (ii) transient fluorescence recovery and (iii) a second quenching component. The initial fast quenching component originates in light harvesting complex II (LHCII) trimers and is dependent upon PsbS and the formation of a proton gradient across the thylakoid membrane (ΔpH). Transient fluorescence recovery is likely to occur in both WT and NoM plants, but it cannot be overcome in NoM due to impaired ΔpH formation and a reduced zeaxanthin synthesis rate. Moreover, an enhanced fluorescence emission peak at ~679 nm in NoM plants indicates detachment of LHCII trimers from the bulk antenna system, which could also contribute to the transient fluorescence recovery. Finally, the second quenching component is triggered by both ΔpH and PsbS and enhanced by zeaxanthin synthesis. This study indicates that minor antenna complexes are not essential for qE, but reveals their importance in electron stransport, ΔpH formation and zeaxanthin synthesis.
非光化学猝灭（NPQ）是叶绿素荧光的过程，其中过量的光能在光合作用膜内无害地耗散。NPQ 的最快组成部分，称为能量依赖猝灭（qE），发生在几分钟内，但 qE 的位点和机制仍存在很大争议。在这里，拟南芥野生型（WT）植物的叶绿素荧光与缺乏所有次要天线复合物（NoM）的突变体进行了比较。在光照下，NoM 表现出改变的叶绿素荧光猝灭诱导（即从暗适应状态），其特征在于三个不同阶段：（i）快速猝灭成分，（ii）瞬态荧光恢复和（iii）第二猝灭成分。初始快速猝灭成分起源于光捕获复合物 II（LHCII）三聚体，并且依赖于 PsbS 和类囊体膜跨膜质子梯度（ΔpH）的形成。瞬态荧光恢复可能发生在 WT 和 NoM 植物中，但由于 ΔpH 形成受损和玉米黄质合成速率降低，NoM 植物中无法克服瞬态荧光恢复。此外，NoM 植物中约 679nm 的增强荧光发射峰表明 LHCII 三聚体从大量天线系统中分离出来，这也可能导致瞬态荧光恢复。最后，第二猝灭成分由 ΔpH 和 PsbS 触发，并通过玉米黄质合成增强。本研究表明，次要天线复合物对于 qE 不是必需的，但揭示了它们在电子传递、ΔpH 形成和玉米黄质合成中的重要性。
