Herbicide Metabolism and Tolerance in the Transgenic Rice Plants Expressing Human CYP2C9 and CYP2C19

Enhanced expression of CYP2C9 and tolerance to sulfonylurea herbicides in transgenic rice plants

“…The proposed metabolic pathway for imazosulfuron in the transgenic rice plants is shown in Figure 4A. CYP2C9 is supposed to produce hydroxyimazosulfuron (Inui et al 2001a), but in our experiments only IPSN was detected. The metabolization of imazosulfuron was enhanced in the pIJU2C9-transformed plants relative to the non-transgenic plants.…”

“…We previously reported that the pIES2C9 transgenic rice acquired the ability to metabolize chlorsulfuron and imazosulfuron, resulted in their tolerance to these herbicides (Inui et al 2001a). We focused on the level of gene expression and the strength of tolerance to sulfonylurea herbicides.…”

“…The cauliflower mosaic virus (CaMV) 35S promoter region of pIJ2C9 was replaced with maize polyubiquitin 1 promoter and the first exon and intron (1992 bp, accession number S94464) (Christensen et al 1992), which was provided by Dr. H. Ichikawa and S. Toki (NIAS, Tsukuba, Japan) to construct pIJU2C9. Expression vector pIES6, which carries a chimeric CaMV 35S promoter containing the seven-tandem enhancer region and 5Ј-untranslated region from the coat protein mRNA of alfalfa mosaic virus (AMV), was used to construct pIES2C9 (Figure 1) (Inui et al 2001a). The chimeric CaMV 35S promoter with the seven-tandem enhancer sequence region enabled effective expression in transgenic tobacco and rice plants (Mitsuhara et al 1996).…”

“…In our previous report, the transgenic rice expressing CYP2C9 under the control of an enhanced chimeric CaMV 35S promoter showed tolerance to chlorsulfuron and imazosulfuron due to metabolism of these herbicides by introduced CYP2C9 (Inui et al 2001a). In the present study, to obtain transgenic rice plants with higher activities of introduced P450, we examined three different transgenic rice using different promoters; either the CaMV 35S promoter, an enhanced chimeric CaMV 35S promoter with a 5Ј-untranslated region, or a maize polyubiquitin 1 promoter with the first exon and first intron of its gene (Christensen et al 1992).…”

“…Transgenic plants harboring such drugmetabolizing P450 genes from mammals were expected to be tolerant to herbicides and to be able to clean up residual agrochemicals (Ohkawa et al 1999). We have already produced several kinds of transgenic rice plants expressing genes for human P450s (i.e., CYP1A1, CYP2C9, and CYP2C19 under the control of CaMV 35S or chimeric CaMV 35S promoters), and evaluated their tolerance to and metabolization of herbicides (Inui et al 2001a;Kawahigashi et al 2003). We considered plants expressing CYP2C9 to be an important goal, because the CYP2C9 enzyme metabolizes the sulfonylurea herbicides imazosulfuron, chlorsulfuron, and triasulfuron (Inui et al 2001b).…”