Mechanism of the Down Regulation of Photosynthesis by Blue Light in the Cyanobacterium Synechocystis sp. PCC 6803

Citations Over TimeTop 10% of 2006 papers

Abstract

Exposure to blue light has previously been shown to induce the reversible quenching of fluorescence in cyanobacteria, indicative of a photoprotective mechanism responsible for the down regulation of photosynthesis. We have investigated the molecular mechanism behind fluorescence quenching by characterizing changes in excitation energy transfer through the phycobilin pigments of the phycobilisome to chlorophyll with steady-state and time-resolved fluorescence excitation and emission spectroscopy. Quenching was investigated in both a photosystem II-less mutant, and DCMU-poisoned wild-type Synechocystis sp. PCC 6803. The action spectra for blue-light-induced quenching was identical in both cell types and was dominated by a band in the blue region, peaking at 480 nm. Fluorescence quenching and its dark recovery was inhibited by the protein cross-linking agent glutaraldehyde, which could maintain cells in either the quenched or the unquenched state. We found that high phosphate concentrations that inhibit phycobilisome mobility and the regulation of energy transfer by the light-state transition did not affect blue-light-induced fluorescence quenching. Both room temperature and 77 K fluorescence emission spectra revealed that fluorescence quenching was associated with phycobilin emission. Quenching was characterized by a decrease in the emission of allophycocyanin and long wavelength phycobilisome terminal emitters relative to that of phycocyanin. A global analysis of the room-temperature fluorescence decay kinetics revealed that phycocyanin and photosystem I decay components were unaffected by quenching, whereas the decay components originating from allophycocyanin and phycobilisome terminal emitters were altered. Our data support a regulatory mechanism involving a protein conformational change and/or change in protein-protein interaction which quenches excitation energy at the core of the phycobilisome.

Related Papers

• → Content of phycoerythrin, phycocyanin, alophycocyanin and phycoerythrocyanin in some cyanobacterial strains: Applications(2018)49 cited
• → Light Regulation of Phycobilisome Structure and Gene Expression in Spirulina platensis C1 (Arthrospira sp. PCC 9438)(1999)42 cited
• → Mercury Induces Alteration of Energy Transfer in Phycobilisome by Selectively Affecting the Pigment Protein, Phycocyanin, in the Cyanobacterium, Spirulina platensis(1991)31 cited
• → Resonance Raman spectra of phycocyanin, allophycocyanin and phycobilisomes from blue - green alga Anacystis nidulans(1985)21 cited
• → Native and in vitro-associated phycobilisomes of Nostoc sp. Composition, energy transfer, and effect of antibodies(1983)5 cited