Molecular Cloning of Novel Cytochrome P450 Species Induced by Chemical Treatments in Cultured Tobacco Cells

We describe the isolation of four cDNA clones from 2,4-D-treated cultured tobacco cells encoding novel P450 species inducible by chemical treatments. RNA blot analysis showed that mRNA levels corresponding to CYP71AI I, CYP81B2, CYP81CI, and CYP81C2 genes were differentially increased by 2,4-D treatment. Furthermore, mRNA levels of CYP71AII, CYP81CI, and CYP81C2 were also increased by treatments with a herbicide safener, naphthalic anhydride, and a plant signaling molecule, salicylic acid, with different kinetics. CYP81 B2 and CYP71 A I I expressed in yeast showed monooxygenase activities toward 7-ethoxycoumarin and the herbicide chlortoluron. These results suggested that CYP71AII, CYP81CI, and CYP81C2 are potential targets for herbicide safeners, and CYP81B2 and CYP71AII are involved in chlortoluron metabolism. In addition, the results suggested the possibility that 2,4-D and naphthalic anhydride may influence not only xenobiotic metabolism but also salicylic acid-dependent responses in tobacco cells.