Herbicide Metabolism and Cross-Tolerance in Transgenic Potato Plants CoExpressing Human CYP1A1, CYP2B6, and CYP2C19

The transgenic potato plants T1977, co-expressing human CYP1A1, CYP2B6, and CYP2C19; S1965, expressing human CYP1A1; S1972, expressing human CYP2B6; and S1974, expressing human CYP2C19 were selected by the combination of kanamycinresistance, PCR, 7-ethoxycoumarin O-deethylase assay, and Western blot analysis. The 7ethoxyresorufin O-deethylase activity of both T1977 and S1965 expressing CYP1A1 were 27 and 53 times higher, respectively, than that of the control. T1977 exhibited remarkable cross-tolerance toward the photosynthesis-inhibiting herbicides atrazine (AT), chlortoluron (CT), and metha-benzthiazuron (MT), the lipid biosynthesis-inhibiting herbicides acetochlor (AC) and metolachlor (MC), and the carotenoid biosynthesis-inhibiting herbicide norflurazon (NR), although the control did not show tolerance toward these herbicides. In addition, T1977 showed high tolerance toward pyributicarb (PC), which inhibits root elongation, whereas S1974 expressing CYP2C19 showed a weak resistance to the herbicide, which was found to be metabolized by CYP2C19 in vitro. S1965, S1972, and S1974 showed crosstolerance toward AT, CT, MT, and NR; AC and MC; and AT, AC, and MC; respectively. These results suggested that T1977 co-expressing CYP1A1, CYP2B6, and CYP2C19 was highly cross-tolerant toward all the herbicides tested, probably by cooperative herbicide metabolism of three P450 species, which were found to metabolize these herbicides in vitro. The transgenic plants expressing human P450 species metabolizing xenobiotics seem to be useful for breeding of herbicide-tolerant crops as well as for phytoremediation of environmental contaminants.