Metabolism of the 4-Hydroxyphenylpyruvate Dioxygenase Inhibitor, Mesotrione, in Multiple-Herbicide-Resistant Palmer amaranth (Amaranthus palmeri)

Abstract

Metabolic resistance to the maize-selective, HPPD-inhibiting herbicide, mesotrione, occurs via Phase I ring hydroxylation in resistant waterhemp and Palmer amaranth; however, mesotrione detoxification pathways post-Phase I are unknown. This research aims to (1) evaluate Palmer amaranth populations for mesotrione resistance via survivorship, foliar injury, and aboveground biomass, (2) determine mesotrione metabolism rates in Palmer amaranth populations during a time course, and (3) identify mesotrione metabolites including and beyond Phase I oxidation. The Palmer amaranth populations, SYNR1 and SYNR2, exhibited higher survival rates (100%), aboveground biomass (c.a. 50%), and lower injury (25–30%) following mesotrione treatment than other populations studied. These two populations also metabolized mesotrione 2-fold faster than sensitive populations, PPI1 and PPI2, and rapidly formed 4-OH-mesotrione. Additionally, SYNR1 and SYNR2 formed 5-OH-mesotrione, which is not produced in high abundance in waterhemp or naturally tolerant maize. Metabolite features derived from 4/5-OH-mesotrione and potential Phase II mesotrione-conjugates were detected and characterized by liquid chromatography–mass spectrometry (LCMS).

Comparative metabolomics and transcriptomics provide new insights into florpyrauxifen-benzyl resistance in Echinochloa glabrescens

“…In a recent comparative transcriptomic analysis between tripyrasulfone-resistant Leptochloa chinensis (L.) Nees and tripyrasulfone-susceptible Leptochloa chinensis (L.) Nees, researchers identified five P450 genes and a GST gene that potentially contribute to metabolic resistance to tripyrasulfone ( Ju et al., 2023 ). While the application of metabolomic technology in weed resistance research is currently at the stage of experimental investigation and exploration, pioneering researchers have utilized Liquid Chromatograph Mass Spectrometer technology to investigate intermediate products and crucial metabolic pathways involved in herbicide metabolism ( Concepcion et al., 2021 ; Strom et al., 2021 ; Concepcion et al., 2024 ). Concepcion et al.…”

“…(2021) identified syncarpic acid-3 (SA3) metabolites via LC-MS-based untargeted metabolomics, revealed a novel reduction–dehydration–GSH conjugation detoxification mechanism. Concepcion et al. (2024) detected and characterized mesotrione metabolites in Palmer amaranth and proposed a detoxification pathway for mesotrione in Multiple-Herbicide-Resistant Palmer amaranth.…”