title: Modification of the water oxidizing complex in leaves of the dgd1 mutant of Arabidopsis thaliana deficient in the galactolipid digalactosyldiacylglycerol.
abstract: The primary biochemical defect in the genetically well characterized dgd1 mutant of Arabidopsis thaliana causes a 90% reduction in the relative amount of the galactolipid digalactosyldiacylglycerol (DGDG). To study the effect of this DGDG deficiency on photosystem II (PS II), time-resolved transients of laser-flash-induced changes of the relative fluorescence quantum yield Fvar,rel(t) were measured in whole leaves from wild-type and the dgd1 mutant. The results obtained reveal (i) in untreated leaves the decay kinetics of Fvar, rel(t) reflecting QA.- reoxidation by endogenous plastoquinone are very similar in wild-type and the dgd1 mutant at room temperature, (ii) the Arrhenius plot of the temperature dependence of electron transfer from QA.- to QB exhibits a break point at about 19 degrees C in wild-type and about 12 degrees C in the dgd1 mutant, (iii) in leaves treated with DCMU the slow reoxidation of QA.- by the PS II donor side is blocked to a much higher extent in the dgd1 mutant (about 50%) compared to wild-type (about 10%), and iv) the normalized amplitude of Fvar,rel(t = 1 micros) reflecting the percentage of fast P680.+ reduction by YZ exhibits a characteristic period four oscillation in wild-type while this feature is strongly damped in the dgd1 mutant. Presumably, the severe DGDG deficiency is causing the thermal down shift of a lipid phase transition that affects the QA.- reoxidation by QB. Most strikingly, the properties of the WOC are modified as a result of reduced DGDG content. Thus, the lipid DGDG appears to be of structural relevance for the WOC.
authors.affiliation: Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Reifarth
authors.forename: G
authors.initials: G
authors.lastname: Christen
authors.forename: A G
authors.initials: AG
authors.lastname: Seeliger
authors.forename: P
authors.initials: P
authors.lastname: Dörmann
authors.forename: C
authors.initials: C
authors.lastname: Benning
authors.forename: G
authors.initials: G
authors.lastname: Renger
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D016227:Benzoquinones / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology; D038983:Galactolipids; D006017:Glycolipids / Q000235:genetics / Q000378:metabolism*; D006540:Herbicides / Q000494:pharmacology; D009154:Mutation; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D045332:Photosystem II Protein Complex; D018515:Plant Leaves / Q000378:metabolism; D014867:Water / Q000378:metabolism*
chemical_list: D016227:Benzoquinones; D038983:Galactolipids; D006017:Glycolipids; D006540:Herbicides; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C007388:digalactosyldiacylglycerol; D014867:Water; C025232:semiquinone radicals; D004237:Diuron