A novel Phe‐206‐Leu mutation in acetolactate synthase confers resistance to penoxsulam in barnyardgrass (Echinochloa crus‐galli (L.) P. Beauv)

Abstract

BACKGROUND: Barnyardgrass (Echinochloa crus-galli (L.) P. Beauv) has evolved resistance to the acetolactate synthase (ALS) inhibitor penoxsulam which is used to control weeds in rice fields in China. The present study is conducted to identify the target-site resistance (TSR) mechanisms conferring resistance in a penoxsulam-resistant population.RESULTS: The ALS sensitivity in vitro of the resistant population was sixfold lower to penoxsulam than that of the sensitive population. ALS sequencing revealed that no known mutation conferring ALS herbicide resistance was detected. However, a novel mutation Phe-206-Leu was identified in the ALS gene. Additionally, ALS gene expression level of the resistant population was lower than that of the sensitive population. Therefore, the penoxsulam resistance was not due to the overexpression of ALS gene. Molecular docking revealed that this mutation may change the interaction of the penoxsulam-ALS binding and weaken its mutual affinity by approximately 10%. Arabidopsis thaliana transformed with mutant ALS had fourfold greater resistance to penoxsulam and varied cross-resistance to other ALS herbicides than those transformed with sensitive ALS. Mutant and sensitive ALS proteins expressed by the baculovirus system exhibited different in vitro penoxsulam sensitivity levels. Mutant ALS had eightfold lower sensitivity to penoxsulam than sensitive ALS.CONCLUSION: This report provides clear evidence that the ALS mutation at position 206 (Phe-206-Leu) confers penoxsulam resistance in barnyardgrass. Phe-206 was confirmed to be the ninth amino acid residue related to ALS herbicide resistance in weeds.

Metabolism Difference Is Involved in Mesosulfuron-Methyl Selectivity between Aegilops tauschii and Triticum aestivum

“…36 To date, there have been nine mutation sites that could impart resistance to ALS inhibitors. 37 These amino acid mutations occurred at the positions to which herbicides bind and block the opening of channels within the enzymes. 19 Compared with A. tauschii, no amino acid mutation was observed at these nine sites in T. aestivum; however, most mutations occurred at the N-terminus.…”

“…A total of 16 amino acid residues of ALS have been reported to interact with sulfonylurea herbicides . To date, there have been nine mutation sites that could impart resistance to ALS inhibitors . These amino acid mutations occurred at the positions to which herbicides bind and block the opening of channels within the enzymes .…”

Occurrence of Bensulfuron-Methyl Resistance and Target-Site Resistance Mechanisms in Ammannia auriculata Biotypes from Paddy Fields

“…In most cases, target-site mutations in ALS genes are known to cause the high resistance to herbicides in many field-evolved resistant-weed populations. Nine conserved amino acid substitutions (Ala122 and 205, Pro197, Phe206, Asp376, Arg377, Trp574, Ser653, and Gly654) in ALS genes have so far been identified to be closely related to ALS inhibitor resistance [ 9 , 10 , 11 ]. In addition to ALS mutations, metabolic resistance is also an important mechanism of resistance.…”

Target-site and metabolic mechanisms of tolerance to penoxsulam in pond lovegrass (Eragrostis japonica)

“…TSR is conferred by (1) the increasing intrinsic activity of the herbicide target protein that compensates for the herbicide inhibitory action, (2) the change in herbicide target protein genes in the nucleotide sequence, or (3) an increase in gene expression (Massa et al 2011;Yu et al 2010). To date, researchers have identified 29 amino acid substitutions at nine conserved positions in the ALS gene (Fang et al 2022). These positions are and Gly-654 (numbered on the basis of the corresponding sequence of Arabidopsis thaliana) (Fang et al 2022;Yu and Powles 2014).…”