Expression of a soybean cytochrome P450 monooxygenase cDNA in yeast and tobacco enhances the metabolism of phenylurea herbicides

A strategy based on the random isolation and screening of soybean cDNAs enc oding cytochrome p450 monooxygenases (P450s) was used in an attempt to iden tify P450 isozymes involved in herbicide metabolism Nine full-length (or ne ar-full-length) P450 cDNAs representing eight distinct p450 families were i solated by using PCR-based technologies. Five of the soybean P450 cDNAs mer e expressed successfully in yeast, and microsomal fractions generated from these strains were tested for their potential to catalyze the metabolism of 10 herbicides and 1 insecticide, In vitro enzyme assays showed that the ge ne product of one heterologously expressed p450 cDNA (CYP71A10) specificall y catalyzed the metabolism of phenylurea herbicides, converting four herbic ides of this class (fluometuron, linuron, chlortoluron, and diuron) into mo re polar compounds. Analyses of the metabolites suggest that the (CYP71A10 encoded enzyme functions primarily as an N-demethylase with regard to fluom eturon, linuron, and diuron, and as a ring-methyl hydroxylase when chlortol uron is the substrate. In vivo assays using excised leaves demonstrated tha t all four herbicides were more readily metabolized in CYP71A10-transformed tobacco compared with control plants. For linuron and chlortoluron, CYP71A 10-mediated herbicide metabolism resulted in significantly enhanced toleran ce to these compounds in the transgenic plants.