title: Changes in photosynthetic electron transfer and state transitions in an herbicide-resistant D1 mutant from soybean cell cultures.
abstract: Anomalies in photosynthetic activity of the soybean cell line STR7, carrying a single mutation (S268P) in the chloroplastic gene psbA that codes for the D1 protein of the photosystem II, have been examined using different spectroscopic techniques. Thermoluminescence emission experiments have shown important differences between STR7 mutant and wild type cells. The afterglow band induced by both white light flashes and far-red continuous illumination was downshifted by about 4 degrees C and the Q band was upshifted by 5 degrees C. High temperature thermoluminescence measurements suggested a higher level of lipid peroxidation in mutant thylakoid membranes. In addition, the reduction rate of P700(+) was significantly accelerated in STR7 suggesting that the mutation led to an activation of the photosystem I cyclic electron flow. Modulated fluorescence measurements performed at room temperature as well as fluorescence emission spectra at 77 K revealed that the STR7 mutant is defective in state transitions. Here, we discuss the hypothesis that activation of the cyclic electron flow in STR7 cells may be a mechanism to compensate the reduced activity of photosystem II caused by the mutation. We also propose that the impaired state transitions in the STR7 cells may be due to alterations in thylakoid membrane properties induced by a low content of unsaturated lipids.
authors: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092-Seville, Spain. mroncel@us.es
authors: Mercedes
authors: M
authors: Roncel
authors: Inmaculada
authors: I
authors: Yruela
authors: Diana
authors: D
authors: Kirilovsky
authors: Fernando
authors: F
authors: Guerrero
authors: Miguel
authors: M
authors: Alfonso
authors: Rafael
authors: R
authors: Picorel
authors: José M
authors: JM
authors: Ortega
mesh_terms: D002460:Cell Line; D004237:Diuron / Q000494:pharmacology*; D004579:Electron Transport; D006540:Herbicides / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000235:genetics; D007700:Kinetics; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D013025:Glycine max / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D006540:Herbicides; D045332:Photosystem II Protein Complex; D004237:Diuron