Recombinant glutathione transferases from flufenacet‐resistant black‐grass (Alopecurus myosuroides Huds.) form different flufenacet metabolites and differ in their interaction with pre‐ and post‐emergence herbicides

Abstract

BACKGROUND: Black-grass (Alopecurus myosuroides Huds.) has become a problematic weed in cereals in Europe. Besides resistance to post-emergent herbicides becoming increasingly widespread, enhanced metabolism of inhibitors of the synthesis of very-long-chain fatty acids (VLCFAs), such as flufenacet, is evolving. Yet, cross-resistance patterns and evolution of this resistance remains poorly understood. RESULTS:The cDNA sequences of five glutathione transferases (GSTs) upregulated in flufenacet resistant black-grass were identified and used for recombinant protein expression. Moderate to slow detoxification of flufenacet was verified for all candidate GSTs expressed in E. coli, and the most active protein produced flufenacet-alcohol instead of a glutathione conjugate, in the presence of reduced glutathione (GSH). Moreover, cross-resistance to other VLCFA-inhibitors e.g., acetochlor and pyroxasulfone and the ACCase inhibitor fenoxaprop was verified in vitro. Various other herbicides of different modes of action including VLCFA-inhibitors were not detoxified by the candidate GSTs.CONCLUSIONS: As several in planta upregulated GSTs detoxified flufenacet in vitro, the shift in sensitivity observed in blackgrass populations, is likely a result of an additive effect. The polygenic character and the relatively low turnover rate of the individual GSTs may explain the slow evolution of flufenacet resistance. In addition, flufenacet resistance was accompanied by cross-resistance with some, but not all, herbicides of the same mode of action, and furthermore to the ACCase inhibitor fenoxaprop-ethyl. Hence, not only the rotation of herbicide modes of action, but also of individual active ingredients is important for resistance management.

Pyroxasulfone Metabolism in Resistant Lolium rigidum: Is It All Down to GST Activity?

“…Indeed, the fact that the L. rigidum proteins with the highest similarity to pyroxasulfone-metabolizing ALOMY5G35766 also have the highest similarity to the F13 peptide identified as being more abundant in pyroxasulfone-resistant population R-P4 provides circumstantial but convincing evidence that they play a role in resistance, even if this could not be shown by an immunodetection technique.…”

“…Interestingly, a recent screening of five recombinant flufenacet-metabolizing GSTs from blackgrass (Alopecurus myosuroides) showed that one of these GSTs (accession number ALOMY5G35766) was also able to metabolize pyroxasulfone . A comparison of the sequence of this GST with the L.…”

“…rigidum genome revealed that five of the seven sequences with a >80% amino acid identity to ALOMY5G35766 were those that matched most closely to the F13 peptide (Supporting Figure S2). Parcharidou et al noted that flufenacet resistance in blackgrass is due to the additive effect of at least five GSTs, all with relatively low individual rates of herbicide conjugation. It is possible that the same situation exists in L.…”

Current status of community resources and priorities for weed genomics research

“…Similarly, epigenetic modifications have been hypothesized to play a role in NTSR, with much remaining to be explored [ 114 – 116 ]. Untargeted approaches such as genome-wide association, selective sweep scans, linkage mapping, RNA-sequencing, and metabolomic profiling have proven helpful to complement more specific biochemical- and chemo-characterization studies towards the elucidation of NTSR mechanisms as well as their regulation and evolution [ 47 , 117 – 124 ]. Even in cases where resistance has been attributed to TSR, genetic mapping approaches can detect other NTSR loci contributing to resistance (as shown by [ 123 ]) and provide further evidence for the role of TSR mutations across populations.…”

Selective herbicide safening in dicot plants: a case study in Arabidopsis

“…S- metolachlor ( S -MOC), a chloroacetamide herbicide that is normally used with a range of safeners, and flufenacet, an oxyacetanilide herbicide that does not require the use of safeners ( Ducker et al., 2019a ; Ducker et al., 2019b ) were selected for this study. Both herbicides have been confirmed to be detoxified by GSTs ( Ducker et al., 2019a ; Ducker et al., 2019b ; Strom et al., 2021 ; Parcharidou et al., 2023 ). In our experimental approach we first looked for effects of IDF on localized transcript expression of GSTs in root culture and rosette tissues of Arabidopsis.…”