A122S, A205V, D376E, W574L and S653N substitutions in acetolactate synthase (ALS) from Amaranthus palmeri show different functional impacts on herbicide resistance. Issue 2 (9th November 2021)

• Record Type: Journal Article
• Authors: Palmieri, Valeria E; Alvarez, Clarisa E; Permingeat, Hugo R; Perotti, Valeria E
• Is Part Of: Pest management science. Volume 78:Issue 2(2022)
• Page Start: 749
• Page End: 757
• Publication Date: 2021-11-09
• Subjects: Amaranthus palmeri -- acetolactate synthase -- ALS‐inhibiting herbicides -- A122S substitution; Pests -- Control -- Periodicals; Pesticides -- Periodicals; 632.9
• DOI: 10.1002/ps.6688
• Languages: English
• ISSNs: 1526-498X

Abstract

Abstract: BACKGROUND: Amaranthus palmeri S. Watson, a problematic weed infesting summer crops in Argentina, has developed multiple herbicide resistance. Resistance to acetolactate synthase (ALS)‐inhibiting herbicides is particularly common, with high‐level resistance mostly caused by different mutations in the ALS enzyme. Six versions of the enzyme were identified from a resistant A. palmeri population, carrying substitutions D376E, A205V, A122S, A282D, W574L and S653N. This work aims to provide a comparative analysis of these mutants and the wild‐type (WT) enzyme to fully understand the herbicide resistance. Thus, all the versions of the ALS gene from A. palmeri were heterologously expressed and purified to evaluate their kinetics and inhibitory response against imazethapyr, diclosulam, chlorimuron‐ethyl, flucarbazone‐sodium and bispyribac‐sodium. RESULTS: A decrease in catalytic efficiency was detected in the A205V, A122S–A282D, W574L and S653N Ap ALS enzymes, whereas only A205V and W574L substitutions also produced a decrease in the substrate affinity. In vitro ALS inhibition assays confirmed cross‐resistance to almost all the herbicides tested, with the exception of A282D Ap ALS, which was as susceptible as WT Ap ALS. Moreover, the results confirmed that the novel substitution A122S provides cross‐resistance to at least one herbicide within each of the five families of ALS inhibitors, and this property could be explained by a lower number of hydrophobic interactions between the herbicides and the mutant enzyme. CONCLUSION: This is the first report to compare various mutations in vitro from A. palmeri ALS . Our data contribute to understanding the impacts of herbicide resistance in this species. © 2021 Society of Chemical Industry. Abstract : A decrease in catalytic efficiency was detected in resistant acetolactate synthase (ALS) from Amaranthus palmeri, with exception of D376E Ap ALS. The five resistant enzymes displayed different inhibition patterns to ALS‐inhibiting herbicides. The novel substitution A122S provides cross‐resistance to the five herbicides families. The data contribute to our understanding of herbicide resistance impacts.