ΔpH-Dependent Fluorescence Quenching and Its Photoprotective Role in the Unicellular Red Alga Rhodella Violacea |
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Authors: | Ritz M Neverov KV Etienne A-L |
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Institution: | (1) UMR 8543, CNRS, Dynamique des membranes végétales, ENS, 46 rue d'Ulm, 75005 Paris, France |
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Abstract: | Plants have developed various photoprotective mechanisms to resist irradiation stress. One of the photoprotective mechanisms
described in the literature for LHC2-containing organisms involves a down-regulation of photosystem (PS) 2 occurring simultaneously
with the build-up of a proton gradient across the thylakoid membrane (ΔpH). It is often correlated with deepoxidation of xanthophylls
located in LHC2. In Rhodophyta instead of LHC2, the peripheral antenna of PS2 consists of a large extramembrane complex, the phycobilisome (PBS), which
transfers its excitation to the core antennae of PS2 composed of the CP43 and CP47 protein-chlorophyll complexes and there
is no xanthophyll cycle. In the red alga Rhodella violacea a ΔpH-dependent chlorophyll (Chl) a fluorescence quenching can be formed. We characterised this quenching, studied the effects of various irradiances and inhibitors.
Under photoinhibitory conditions, the ΔpH-dependent Chl fluorescence quenching exerts a photoprotective role and delays the
kinetics of photoinhibition. It is the first time that such a photoprotective mechanism is described in PBS-containing organisms.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | chlorophyll irradiance light-harvesting chlorophyll-protein complex photoinhibition photosystems 1 and 2 phycobilisome |
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