Department of Molecular Compound Physics, Center for Physical Sciences and Technology, Sauletekio Ave. 3, LT-10257 Vilnius, Lithuania.
The School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
Biochim Biophys Acta Bioenerg. 2019 Jun 1;1860(6):499-507. doi: 10.1016/j.bbabio.2019.05.002. Epub 2019 May 2.
Plants have developed multiple self-regulatory mechanisms to efficiently function under varying sunlight conditions. At high light intensities, non-photochemical quenching (NPQ) is activated on a molecular level, safely dissipating an excess excitation as heat. The exact molecular mechanism for NPQ is still under debate, but it is widely agreed that the direct participation of the carotenoid pigments is involved, one of the proposed candidate being the zeaxanthin. In this work, we performed fluorescence measurements of violaxanthin- and zeaxanthin-enriched major light-harvesting complexes (LHCII), in ensemble and at the single pigment-protein complex level, where aggregation is prevented by immobilization of LHCIIs onto a surface. We show that a selective enrichment of LHCII with violaxanthin or zeaxanthin affects neither the ability of LHCII to switch into a dissipative conformation nor the maximal level of induced quenching. However, the kinetics of the fluorescence decrease due to aggregation on the timescale of seconds are different, prompting towards a modulatory effect of zeaxanthin in the dynamics of quenching.
植物已经发展出多种自我调节机制，以在变化的光照条件下高效运作。在高强度光照下，非光化学猝灭（NPQ）在分子水平上被激活，将多余的激发能安全地以热量的形式耗散。NPQ 的确切分子机制仍存在争议，但人们普遍认为类胡萝卜素色素的直接参与是其中之一，而被广泛认为的候选物质之一是玉米黄质。在这项工作中，我们在集合体和单个色素-蛋白复合物水平上对富含紫黄质和玉米黄质的主要光捕获复合物（LHCII）进行了荧光测量，其中 LHCII 的固定化防止了聚集。我们表明，LHCII 对紫黄质或玉米黄质的选择性富集既不影响 LHCII 转变为耗散构象的能力，也不影响诱导猝灭的最大水平。然而，由于聚集导致的荧光衰减的动力学在秒的时间尺度上是不同的，这促使玉米黄质在猝灭动力学中发挥调节作用。
