Comparison of herbicide specificity of CYP81A cytochrome P450s from rice and a multiple‐herbicide resistant weed, Echinochloa phyllopogon

Abstract

BACKGROUND: CYP81A cytochrome P450s (CYP81As) play a key role in herbicide detoxification in Poaceae plants. Crop CYP81As confer natural tolerance to multiple herbicides, whereas CYP81As in weeds disrupt herbicide action. Identifying differences in CYP81A herbicide specificity between crops and weeds could provide valuable information for controlling weeds. In this study, we quantitatively compared herbicide specificity between CYP81A6 from rice (Oryza sativa) and CYP81A12 and CYP81A21 from a weed, Echinochloa phyllopogon, using transgenic Escherichia coli and Arabidopsis.RESULTS: All three CYP81As metabolized the five tested herbicides and formed similar metabolites, with the highest relative activities of 400 to 580% toward bentazone compared to their activity on bensulfuron-methyl (defined as 100%). However, they showed differing activity toward propyrisulfuron. The relative activities of Echinochloa phyllopogon CYP81A12 (12.2%) and CYP81A21 (34.4%) toward propyrisulfuron were lower than that of rice CYP81A6 (98.5%). Additionally, rice CYP81A6 produced O-demethylated propyrisulfuron and hydroxylated products, whereas Echinochloa phyllopogon CYP81As produced only hydroxylated products. Arabidopsis expressing CYP81A12 and CYP81A21 exhibited lower levels of resistance against propyrisulfuron compared to that in Arabidopsis expressing CYP81A6. Homology modeling and in silico docking revealed that bensulfuron-methyl docked well into the active centers of all three CYP81As, whereas propyrisulfuron docked into rice CYP81A6 but not into Echinochloa phyllopogon CYP81As.CONCLUSION: The differing herbicide specificity displayed by rice CYP81A6 and Echinochloa phyllopogon CYP81A12 and CYP81A21 will help design inhibitors (synergists) of weed CYP81As, as well as develop novel herbicide ingredients that are selectively metabolized by crop CYP81As, to overcome the problem of herbicide resistance.

Predicting the unpredictable: the regulatory nature and promiscuity of herbicide cross resistance

“…Cross resistance may be caused by a single enzyme or by the combination of multiple ones participating in any of the three phases of herbicide metabolism. For example, single CYP450s and GSTs have been shown to metabolize herbicides from multiple SoA groups 12–17 . Additionally, multiple genes encoding different enzymes can be co‐expressed (and potentially co‐regulated), where each enzyme could play a role in the detoxification process of multiple herbicides.…”

“…A few recent studies in weed science have utilized protein structure prediction with docking simulations. For instance, Ha et al 12 applied a docking analysis for herbicide affinity identification using the identified CYP81A in Echinochloa phyllopogon and its rice homologs. GSTs and UGTs also should be analyzed for their affinity with herbicide molecules.…”

“…For example, single CYP450s and GSTs have been shown to metabolize herbicides from multiple SoA groups. [12][13][14][15][16][17] Additionally, multiple genes encoding different enzymes can be co-expressed (and potentially co-regulated), where each enzyme could play a role in the detoxification process of multiple herbicides. For instance, a study identified that expression of a GST and ABC transporter were co-induced by multiple herbicides from different SoA groups.…”

Molecular Responses and Degradation Mechanisms of the Herbicide Diuron in Rice Crops

“…10 Numerous Phase II metabolites of DU in crops are still unknown and need to be discovered and studied. More importantly, several key herbicide-detoxifying genes encoding metabolizing enzymes have been identified recently, such as CYP81A, CYP709C, ARGT1, and GSTF1, 9,14,15 whereas a substantial knowledge gap still exists in the detoxifying genes responding to DU stress and their genetic regulatory mechanism pertaining to the generation and distribution of DU derivatives in crops. The characterization of herbicidedetoxifying genes and the elucidation of their molecular signal pathway are great advances in understanding the NTSR and supplying useful information for developing crop protection schemes.…”