Mutagenesis of an amino acid responsible in phytoene desaturase from Synechocystis for binding of the bleaching herbicide norflurazon
1994
Martinez-Ferez, I. | Vioque, A. | Sandmann, G.
Synechocystis mutants were selected resistant against the bleaching herbicide norflurazon. In vitro analysis of phytoene desaturation demonstrated that they all possess a resistant enzyme. Sequencing of the corresponding pds gene revealed that three different point mutations were obtained. In all cases, the same amino acid, Arg195 was modified either into Cys, Pro, or Ser. The degree of resistance determined via carotenoid formation in cells as well as cell-free phytoene desaturation in the presence of norflurazon was highest when Arg was changed to Ser. A modification to Pro or to Cys resulted in a gradually less pronounced degree of resistance. Cross-resistance toward other bleaching herbicides like fluridone, flurtamone, or fluorochloridone was also studied. However, there was only a slight resistance against fluridone in one and against flurtamone in two of the mutants. In contrast to other cyanobacterial mutants previously described, impairment of catalytic activities of the mutated enzymes was negligible.
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