The Xanthophyll Cycle Modulates the Kinetics of Nonphotochemical Energy Dissipation in Isolated Light-Harvesting Complexes, Intact Chloroplasts, and Leaves of Spinach1
AUTOR(ES)
Ruban, Alexander V.
FONTE
American Society of Plant Physiologists
RESUMO
We analyzed the kinetics of nonphotochemical quenching of chlorophyll fluorescence (qN) in spinach (Spinacia oleracea) leaves, chloroplasts, and purified light-harvesting complexes. The characteristic biphasic pattern of fluorescence quenching in dark-adapted leaves, which was removed by preillumination, was evidence of light activation of qN, a process correlated with the de-epoxidation state of the xanthophyll cycle carotenoids. Chloroplasts isolated from dark-adapted and light-activated leaves confirmed the nature of light activation: faster and greater quenching at a subsaturating transthylakoid pH gradient. The light-harvesting chlorophyll a/b-binding complexes of photosystem II were isolated from dark-adapted and light-activated leaves. When isolated from light-activated leaves, these complexes showed an increase in the rate of quenching in vitro compared with samples prepared from dark-adapted leaves. In all cases, the quenching kinetics were fitted to a single component hyperbolic function. For leaves, chloroplasts, and light-harvesting complexes, the presence of zeaxanthin was associated with an increased rate constant for the induction of quenching. We discuss the significance of these observations in terms of the mechanism and control of qN.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=32130Documentos Relacionados
- Reconstitution of chlorophyll a/b light-harvesting complexes: Xanthophyll-dependent assembly and energy transfer
- Induction of Nonphotochemical Energy Dissipation and Absorbance Changes in Leaves (Evidence for Changes in the State of the Light-Harvesting System of Photosystem II in Vivo).
- The Effects of Illumination on the Xanthophyll Composition of the Photosystem II Light-Harvesting Complexes of Spinach Thylakoid Membranes.
- Photoinhibition and Zeaxanthin Formation in Intact Leaves 12: A Possible Role of the Xanthophyll Cycle in the Dissipation of Excess Light Energy
- Energy transfer in spectrally inhomogeneous light-harvesting pigment-protein complexes of purple bacteria.