Metabolism of the Herbicide Chlortoluron in Transgenic Tobacco Plants Expressing the Fused Enzyme between Rat Cytochrome P4501A1 and Yeast NADPH-Cytochrome P450 Oxidoreductase

Abstract Metabolism of the herbicide chlortoluron was examined in transgenic tobacco plants expressing the genetically engineered fused enzyme between rat cytochrome P4501A1 and yeast NADPH-cytochrome P450 oxidoreductase. The transgenic plants were resistant to chlortoluron at concentrations of 10 to 50 μ M in Murashige and Skoog medium; however, 10 μ M was toxic to control plants. There were no significant differences in the uptake and the translocation of [ 14 C] chlortoluron between transgenic and control plants. The major metabolites produced by transgenic plants were N -demethylated metabolite, 4-carboxyphenyl metabolite, and their conjugates, whereas only the N -demethylated metabolite was produced by control plants. In vitro studies also confirmed that the fused enzyme expressed in the microsomal fraction of the transgenic plants exhibited both ring-methyl hydroxylation and N -demethylation activities toward chlor-toluron. These results suggested that the transgenic tobacco plants expressing the fused enzyme metabolized chlortoluron to yield larger amounts of nonphytotoxic metabolites, resulting in tolerance to the herbicide.