Is PsbS the site of non-photochemical quenching in photosynthesis?
ABSTRACT The PsbS protein of photosystem II functions in the regulation of photosynthetic light harvesting. Along with a low thylakoid lumen pH and the presence of de-epoxidized xanthophylls, PsbS is necessary for photoprotective thermal dissipation (qE) of excess absorbed light energy in plants, measured as non-photochemical quenching of chlorophyll fluorescence. What is known about PsbS in relation to the hypothesis that this protein is the site of qE is reviewed here.
SourceAvailable from: Carsten Külheim
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ABSTRACT: Climate change will increase autumn air temperature, while photoperiod decrease will remain unaffected. We assessed the effect of increased autumn air temperature on timing and development of cold acclimation and freezing resistance in Eastern white pine (EWP, Pinus strobus) under field conditions. For this purpose we simulated projected warmer temperatures for southern Ontario in a Temperature Free-Air-Controlled Enhancement (T-FACE) experiment and exposed EWP seedlings to ambient (Control) or elevated temperature (ET, +1.5°C/+3°C during day/night). Photosynthetic gas exchange, chlorophyll fluorescence, photoprotective pigments, leaf non-structural carbohydrates (NSC), and cold hardiness were assessed over two consecutive autumns. Nighttime temperature below 10°C and photoperiod below 12 h initiated downregulation of assimilation in both treatments. When temperature further decreased to 0°C and photoperiod became shorter than 10 h, downregulation of the light reactions and upregulation of photoprotective mechanisms occurred in both treatments. While ET seedlings did not delay the timing of the downregulation of assimilation, stomatal conductance in ET seedlings was decreased by 20–30% between August and early October. In both treatments leaf NSC composition changed considerably during autumn but differences between Control and ET seedlings were not significant. Similarly, development of freezing resistance was induced by exposure to low temperature during autumn, but the timing was not delayed in ET seedlings compared to Control seedlings. Our results indicate that EWP is most sensitive to temperature changes during October and November when downregulation of photosynthesis, enhancement of photoprotection, synthesis of cold-associated NSCs and development of freezing resistance occur. However, we also conclude that the timing of the development of freezing resistance in EWP seedlings is not affected by moderate temperature increases used in our field experiments.Frontiers in Plant Science 03/2015; 6(165). DOI:10.3389/fpls.2015.00165 · 3.64 Impact Factor
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ABSTRACT: In the present study, we performed an integrated proteomics (2DE) and metabolomics (HPLC-MS) investigation to determine the molecular mechanisms underlying cadmium (Cd) tolerance in the halophyte Cakile maritima. Recent physiological reports have documented how C. maritima could accumulate high doses of Cd in roots and shoots, while appearing to be naturally equipped to cope with it, since mild or heavy Cd stress did not alter physiological parameters, including mineral uptake, pigment contents, other than transpiration, water use efficiency and variation of net CO2 assimilation. In the present study, metabolomics and proteomics results highlighted the Cd-dependent up-regulation of thiol compound anabolism, including glutathione and phytochelatin homeostasis, especially in response to elevated Cd stress (100 µM), which allows an intracellular chelation of Cd and its compartmentalization into vacuole. Altered energy metabolism at the triose phosphate level was accompanied by altered accumulation of Calvin cycle intermediates and photorespiration byproducts at high (100 µM), albeit not at mild (25 µM), CdCl2 stress, suggesting that elevated doses of Cd might promote photorespiration. Metabolomics results confirmed proteomics and previous physiological evidence, also suggesting that osmoprotectants betaine and proline, together with plant hormones methyl jasmonate and salicylic acid might be involved in mediating responses to Cd-induced stress. Taken together, from the present study we conclude that C. maritima might represent an ideal candidate for phytoremediation interventions in Cd-contaminated soils.Molecular BioSystems 01/2015; 11(4). DOI:10.1039/C4MB00567H · 3.18 Impact Factor