title: Functional aspects of the photosynthetic light reactions in heat stressed Arabidopsis deficient in digalactosyl-diacylglycerol.
abstract: Plants are often submitted, in their natural environment, to various abiotic stresses such as heat stress. However, elevated temperature has a detrimental impact on overall plant growth and development. We have examined the physiological response of the dgd1-2 and dgd1-3 Arabidopsis mutants lacking 30-40% of digalactosyl-diacylglycerol (DGDG) exposed to heat constraint. These mutants, which grow similarly to wild type under normal conditions, were previously reported to be defective in basal thermotolerance as measured by cotyledon development. However their functional properties were not described. Chlorophyll fluorescence measurements and absorbance changes at 820nm were used to monitor photosystem II (PSII) and PSI activity, respectively. It was observed that both mutants have similar photosystem activities with some differences. The mutants were less able to use near saturation light energy and elicited higher rates of cyclic PSI electron flow compare to wild type. Arabidopsis leaves exposed to short-term (5min) mild (40°C) or strong (44°C) heat treatment have shown a decline in the operating effective quantum yield of PSII and in the proportion of active PSI reaction centers. However, cyclic PSI electron flow was enhanced. The establishment of the energy-dependent non-photochemical quenching of chlorophyll fluorescence was accelerated but its decline under illumination was inhibited. Furthermore, heat stress affected the process implicated in the redistribution of light excitation energy between the photosystems known as the light state transitions. All the effects of heat stress mentioned above were more intense in the mutant leaves with dgd1-3 being even more susceptible. The decreased DGDG content of the thylakoid membranes together with other lipid changes are proposed to influence the thermo-sensitivity of the light reactions of photosynthesis towards heat stress.
authors: Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières, Trois-Rivières, Québec G9A 5H7, Canada.
authors: Jemâa
authors: J
authors: Essemine
authors: Sridharan
authors: S
authors: Govindachary
authors: Saïda
authors: S
authors: Ammar
authors: Sadok
authors: S
authors: Bouzid
authors: Robert
authors: R
authors: Carpentier
mesh_terms: D000064:Acclimatization / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport / Q000502:physiology; D038983:Galactolipids / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature / Q000009:adverse effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000502:physiology; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects*; D045331:Photosystem I Protein Complex / Q000502:physiology / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000502:physiology / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D013312:Stress, Physiological; D020524:Thylakoids / Q000378:metabolism; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D038983:Galactolipids; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; C007388:digalactosyldiacylglycerol; D002734:Chlorophyll