Flavonoid-based inhibitors of the Phi-class glutathione transferase from black-grass to combat multiple herbicide resistance

Schwarz, Maria; Eno, Rebecca F.M.; Freitag-Pohl, Stefanie; Coxon, Christopher R.; Straker, Hannah E.; Wortley, David J.; Hughes, David J.; Mitchell, Glynn; Moore, Jenny; Cummins, Ian; Onkokesung, Nawaporn; Brazier-Hicks, Melissa; Edwards, Robert; Pohl, Ehmke; Steel, Patrick G.

Abstract

The evolution and growth of multiple-herbicide resistance (MHR) in grass weeds continues to threaten global cereal production. While various processes can contribute to resistance, earlier work has identified the phi class glutathione-S-transferase (AmGSTF1) as a functional biomarker of MHR in black-grass (Alopecurus myosuroides). This study provides further insights into the role of AmGSTF1 in MHR using a combination of chemical and structural biology. Crystal structures of wild-type AmGSTF1, together with two specifically designed variants that allowed the co-crystal structure determination with glutathione and a glutathione adduct of the AmGSTF1 inhibitor 4-chloro-7-nitro-benzofurazan (NBD-Cl) were obtained. These studies demonstrated that the inhibitory activity of NBD-Cl was associated with the occlusion of the active site and the impediment of substrate binding. A search for other selective inhibitors of AmGSTF1, using ligand-fishing experiments, identified a number of flavonoids as potential ligands. Subsequent experiments using black-grass extracts discovered a specific flavonoid as a natural ligand of the recombinant enzyme. A series of related synthetic flavonoids was prepared and their binding to AmGSTF1 was investigated showing a high affinity for derivatives bearing a O-5-decyl-α-carboxylate. Molecular modelling based on high-resolution crystal structures allowed a binding pose to be defined which explained flavonoid binding specificity. Crucially, high binding affinity was linked to a reversal of the herbicide resistance phenotype in MHR black-grass. Collectively, these results present a nature-inspired new lead for the development of herbicide synergists to counteract MHR in weeds.

Citation

Schwarz, M., Eno, R. F., Freitag-Pohl, S., Coxon, C. R., Straker, H. E., Wortley, D. J., Hughes, D. J., Mitchell, G., Moore, J., Cummins, I., Onkokesung, N., Brazier-Hicks, M., Edwards, R., Pohl, E., & Steel, P. G. (2021). Flavonoid-based inhibitors of the Phi-class glutathione transferase from black-grass to combat multiple herbicide resistance. Organic and Biomolecular Chemistry, 19(42), 9211-9222. https://doi.org/10.1039/d1ob01802g

• Journal Article Type: Article
• Acceptance Date: Sep 30, 2021
• Online Publication Date: Oct 13, 2021
• Publication Date: Nov 14, 2021
• Deposit Date: Oct 19, 2021
• Publicly Available Date: Jan 10, 2022
• Journal: Organic & Biomolecular Chemistry
• Print ISSN: 1477-0520
• Electronic ISSN: 1477-0539
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 19
• Issue: 42
• Pages: 9211-9222
• DOI: https://doi.org/10.1039/d1ob01802g
• Public URL: https://durham-repository.worktribe.com/output/1231338