Herbicide Metabolism and Cross-Tolerance in Transgenic Potato Plants Expressing Human CYP1A1

Transgenic potato plants expressing human CYP1A1 and human CYP1A1/yeast NADPHcytochrome P450 reductase (YR) fused enzyme were generated from microtubers by the use of an Agrobacterium transformation system. The transgenic plants S1384 expressing human CYP1A1 and both F1386 and F1515 expressing the fused enzyme were selected by kanamycin resistance, PCR analysis, chlortoluron (CT) resistance, and Western blot analysis. The integration and transcription of the corresponding CYP1A1 genes were confirmed in these selected transgenic plants by Southern and Northern blot analyses. CYP1A1 and its fused proteins were found to be produced in the transgenic plants S1384 and F1515, respectively. The P450-dependent monooxygenase activity of the transgenic plants S1384, S1386, and F1515 was 3.5, 4.2, and 3.8 times higher in 7-ethoxycoumarin 0-deethylation in vitro and 6.4, 5.8, and 5.3 times higher in [14C]CT metabolism in vivo than those of the control plants, respectively. In the metabolism of [14C]atrazine (AT), four metabolites were found in both control and transgenic plants. The deisopropylated deethylated metabolite DIDE, which is nonphytotoxic, was produced to a higher extent in S1384 and F1515 compared with the control. With herbicide tolerance tests, S1384 showed tolerance toward both AT and pyriminobac-methyl (PM), and F1386 and F1515 were tolerant toward PM, while the control died by treatment with both herbicides. Thus, it was found that the transgenic potato plants expressing human CYP1A1 metabolized the herbicides CT and AT with different structures and herbicide modes of action and resulted in cross-tolerance to both herbicides as well as PM.