CYP81A68 confers metabolic resistance to ALS and ACCase-inhibiting herbicides and its epigenetic regulation in Echinochloa crus-galli

Long-term and excessive herbicide use has led to some environmental concerns and especially, herbicide resistance evolution in weeds. Here, we confirmed acetolactate synthase (ALS) inhibiting herbicide penoxsulam resistance and cross resistance to acetyl-coenzyme carboxylase (ACCase) inhibiting herbicides (cyhalofop-butyl and metamifop) in a global weed Echinochloa crus-galli population resistant to these herbicides (R). Penoxsulam metabolism study indicated that degradation rate was significantly higher in R than susceptible E. crus-galli population (S). RNA-sequencing revealed that a cytochrome P450 (P450) gene, CYP81A68, expressed higher in R versus S. Rice seedlings overexpressing this CYP81A68 gene are resistant to penoxsulam, cyhalofop-butyl and metamifop, and penoxsulam resistance is due to enhanced metabolism via O-demethylation. Deletion analysis of the CYP81A68 gene promoter identified an efficient region, in which differential methylation of CpG islands occurred between R and S. Collectively, these results demonstrate that upregulation of E. crus-galli CYP81A68 gene endows generalist metabolic resistance to commonly used ALS- and ACCase-inhibiting herbicides in rice fields and epigenetic regulation may play a role in the resistance evolution. This research could contribute to strategies reducing herbicide environmental impacts by judicious selection of alternative herbicide and nonchemical control tactics.

Automated summary

Long-term and excessive herbicide use has led to the evolution of herbicide resistance in weeds. This study confirmed the resistance of a global weed population, Echinochloa crus-galli, to ALS-inhibiting herbicide penoxsulam and ACCase-inhibiting herbicides cyhalofop-butyl and metamifop. The resistance was found to be due to the higher expression of a cytochrome P450 gene, CYP81A68, and enhanced metabolism via O-demethylation. Epigenetic regulation, specifically differential methylation of CpG islands, was also observed between resistant and susceptible populations. This research highlights the importance of alternative herbicide selection and nonchemical control tactics in reducing environmental impacts.