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

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.

Metabolism-Based Herbicide Resistance and Cross-Resistance in Crop Weeds: A Threat to Herbicide Sustainability and Global Crop Production

“…Identifying the genes endowing metabolic resistance in weedy plants, and their regulation, are challenging but now underway in L. rigidum (Gaines et al, 2014), A. myosuroides (Cummins et al, 2013), and E. phyllopogon (Iwakami et al, 2014a(Iwakami et al, , 2014b. A collaborative effort across Australia and Europe is beginning to tackle metabolic resistance in major crop weeds.…”

“…For example, two P450 genes (CYP71AK2 and CYP72A) were recently found to be highly induced by bispyribacsodium in multiple herbicide-resistant plants (Iwakami et al, 2014b). More recently, the two P450 genes (CYP81A12 and CYP81A21) identified in a resistant E. phyllopogon population conferred resistance to certain metabolizable herbicides when expressed in Arabidopsis, and yeast (Saccharomyces cerevisiae WAT11 strain)-expressed CYP81A12 and CYP81A21 enzymes metabolized herbicide through O-demethylation (Iwakami et al, 2014a). These two highly similar P450 genes (likely homologs) are likely to be up-regulated simultaneously by a single transacting element in the resistant individuals (Iwakami et al, 2014a).…”

“…More recently, the two P450 genes (CYP81A12 and CYP81A21) identified in a resistant E. phyllopogon population conferred resistance to certain metabolizable herbicides when expressed in Arabidopsis, and yeast (Saccharomyces cerevisiae WAT11 strain)-expressed CYP81A12 and CYP81A21 enzymes metabolized herbicide through O-demethylation (Iwakami et al, 2014a). These two highly similar P450 genes (likely homologs) are likely to be up-regulated simultaneously by a single transacting element in the resistant individuals (Iwakami et al, 2014a). Therefore, based on available studies on metabolic resistance genetics and P450 gene discovery in weedy species, a single P450 can confer resistance to a few herbicides, as has been reported in herbicide-tolerant crops (e.g.…”

Differential Expression of Genes Associated With Degradation Enhancement of Imazethapyr in Barnyardgrass (Echinochloa crus-galli)

“…Similarly, a CYP81 gene is involved in the resistance of A. japonicus to the herbicide fenoxaprop-P-ehtyl (Chen, Xu, Zhang, Bai, & Dong, 2018). In E. phyllopogon, the higher expressions of the CYP81A12 and CYP81A21 genes are associated with resistance to the ALS-inhibiting herbicides penoxsulam and bensulfuron-methyl (Iwakami et al, 2014a). In this species, previous spraying of bispyribac-sodium, another ALS inhibitor, induced the expression of CYP71AK2 and CYP72A254 genes in plants resistant to these herbicides (Iwakami et al, 2014b).…”

“…(Délye, Gardin, Boucansaud, Chauvel, & Petit, 2011) and Echinochloa phyllopogon Stapf. (Yasour et al, 2009;Iwakami et al, 2014a). The main enzymes related with herbicide detoxification include cytochrome P450 monooxygenases (known as CYP or P450) and glutathione S-transferases (GST) (Powles & Yu, 2010).…”