Ultrafast fluorescence study on the location and mechanism of non-photochemical quenching in diatoms |
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Authors: | Yuliya Miloslavina Petar H Lambrev Reimund Goss Alfred R Holzwarth |
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Institution: | a Max-Planck-Institut für Bioanorganische Chemie, Stiftstraβe 34-36, D-45470 Mülheim a.d. Ruhr, Germany b Universität Leipzig, Institut für Biologie I, Abteilung Pflanzenphysiologie, Johannisallee 21-23, D-04103 Leipzig, Germany |
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Abstract: | The diatom algae, responsible for at least a quarter of the global photosynthetic carbon assimilation in the oceans, are capable of switching on rapid and efficient photoprotection, which helps them cope with the large fluctuations of light intensity in the moving waters. The enhanced dissipation of excess excitation energy becomes visible as non-photochemical quenching (NPQ) of chlorophyll a fluorescence. Intact cells of the diatoms Cyclotella meneghiniana and Phaeodactylum tricornutum, which show different NPQ induction kinetics under high light illumination, were investigated by picosecond time-resolved fluorescence under dark and NPQ-inducing high light conditions. The fluorescence kinetics revealed that there are two independent sites responsible for NPQ. The first quenching site is located in an FCP antenna system that is functionally detached from both photosystems, while the second quenching site is located in the PSII-attached antenna. Notwithstanding their different npq induction and reversal kinetics, both diatoms showed identical NPQ via both mechanisms in the steady-state. Their fluorescence decays in the dark-adapted states were different, however. A detailed quenching model is proposed for NPQ in diatoms. |
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Keywords: | Chl chlorophyll DCMU 3-(3&prime 4&prime -dichlorphenyl)-1 1-dimethylurea DdC diadinoxanthin cycle Ddx diadinoxanthin DAS decay associated spectra DES de-epoxidation state Dtx diatoxanthin FCPs fucoxanthin-chlorophyll-binding proteins HL high light LHC light-harvesting complex NPQ non-photochemical quenching ΔpH transthylakoid proton gradient PS photosystem RC reaction centre RP radical pair XC xanthophyll cycle Zx zeaxanthin |
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