Cytochrome P450 CYP81A12 and CYP81A21 Are Associated with Resistance to Two Acetolactate Synthase Inhibitors in Echinochloa phyllopogon

Satoshi Iwakami; Masaki Endo; Hiroaki Saika; Junichi Okuno; Naoki Nakamura; Masao Yokoyama; Hiroaki Watanabe; Seiichi Toki; Akira Uchino; Tatsuya Inamura

doi:10.1104/pp.113.232843

Cytochrome P450 CYP81A12 and CYP81A21 Are Associated with Resistance to Two Acetolactate Synthase Inhibitors in Echinochloa phyllopogon

Plant Physiol. 2014 Jun;165(2):618-629. doi: 10.1104/pp.113.232843. Epub 2014 Apr 23.

Authors

Affiliations

¹ Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan (S.I., T.I.);Plant Genome Engineering Research Unit, Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan (M.E., H.S., S.T.);The Japan Association for Advancement of Phyto-Regulators, Ushiku 300-1211, Japan (J.O., N.N., M.Y.); andCrop Production Systems Division, NARO Agricultural Research Center, Tsukuba 305-8666, Japan (H.W., A.U.).
² Graduate School of Agriculture, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan (S.I., T.I.);Plant Genome Engineering Research Unit, Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan (M.E., H.S., S.T.);The Japan Association for Advancement of Phyto-Regulators, Ushiku 300-1211, Japan (J.O., N.N., M.Y.); andCrop Production Systems Division, NARO Agricultural Research Center, Tsukuba 305-8666, Japan (H.W., A.U.) uchino@affrc.go.jp.

Abstract

Previous studies have demonstrated multiple herbicide resistance in California populations of Echinochloa phyllopogon, a noxious weed in rice (Oryza sativa) fields. It was suggested that the resistance to two classes of acetolactate synthase-inhibiting herbicides, bensulfuron-methyl (BSM) and penoxsulam (PX), may be caused by enhanced activities of herbicide-metabolizing cytochrome P450. We investigated BSM metabolism in the resistant (R) and susceptible (S) lines of E. phyllopogon, which were originally collected from different areas in California. R plants metabolized BSM through O-demethylation more rapidly than S plants. Based on available information about BSM tolerance in rice, we isolated and analyzed P450 genes of the CYP81A subfamily in E. phyllopogon. Two genes, CYP81A12 and CYP81A21, were more actively transcribed in R plants compared with S plants. Transgenic Arabidopsis (Arabidopsis thaliana) expressing either of the two genes survived in media containing BSM or PX at levels at which the wild type stopped growing. Segregation of resistances in the F2 generation from crosses of R and S plants suggested that the resistance to BSM and PX were each under the control of a single regulatory element. In F6 recombinant inbred lines, BSM and PX resistances cosegregated with increased transcript levels of CYP81A12 and CYP81A21. Heterologously produced CYP81A12 and CYP81A21 proteins in yeast (Saccharomyces cerevisiae) metabolized BSM through O-demethylation. Our results suggest that overexpression of the two P450 genes confers resistance to two classes of acetolactate synthase inhibitors to E. phyllopogon. The overexpression of the two genes could be regulated simultaneously by a single trans-acting element in the R line of E. phyllopogon.