Metabolism of the herbicide chlortoluron in transgenic tobacco plants expressing the fused enzyme between rat cytochrome P4501A1 and yeast NADPH-cytochrome P450 oxidoreductase

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 1D to 50 mu M in Murashige and Skoog medium; however, 10 mu M was toxic to control plants. There were no significant differences in the uptake and the translocation of [C-14] 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 chlortoluron. 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. (C) 1996 Academic Press, Inc.