Changes in the proteome of the problem weed blackgrass correlating with multiple‐herbicide resistance

Abstract

SummaryHerbicide resistance in grass weeds is now one of the greatest threats to sustainable cereal production in Northern Europe. Multiple‐herbicide resistance (MHR), a poorly understood multigenic and quantitative trait, is particularly problematic as it provides tolerance to most classes of chemistries currently used for post‐emergence weed control. Using a combination of transcriptomics and proteomics, the evolution of MHR in populations of the weed blackgrass (Alopecurus myosuroides) has been investigated. While over 4500 genes showed perturbation in their expression in MHR versus herbicide sensitive (HS) plants, only a small group of proteins showed >2‐fold changes in abundance, with a mere eight proteins consistently associated with this class of resistance. Of the eight, orthologues of three of these proteins are also known to be associated with multiple drug resistance (MDR) in humans, suggesting a cross‐phyla conservation in evolved tolerance to chemical agents. Proteomics revealed that MHR could be classified into three sub‐types based on the association with resistance to herbicides with differing modes of action (MoA), being either global, specific to diverse chemistries acting on one MoA, or herbicide specific. Furthermore, the proteome of MHR plants were distinct from that of HS plants exposed to a range of biotic (insect feeding, plant–microbe interaction) and abiotic (N‐limitation, osmotic, heat, herbicide safening) challenges commonly encountered in the field. It was concluded that MHR in blackgrass is a uniquely evolving trait(s), associated with changes in the proteome that are distinct from responses to conventional plant stresses, but sharing common features with MDR in humans.

Herbicide Metabolism: Crop Selectivity, Bioactivation, Weed Resistance, and Regulation

“…This suggested that GSTs must possess alternative protective activities in NTSR that do not directly involve herbicide detoxification. However, it is known that the complex NTSR trait in different weed species is multi-genic (Duhoux et al 2017b;Keith et al 2017;Tétard-Jones et al, 2018), suggesting that a single GST cannot confer multiple resistance alone. In further investigating the roles of these proteins in NTSR, we now report the detailed characterization of the all detectable GSTs (the 'GSTome'), associated with herbicide resistance using a combination of transcriptomics, proteomics and functional expression of the respective recombinant enzymes.…”

“…As described above, from the growing body of transcriptome data, it is clear that GSTs from different classes are associated with NTSR in many weed species. Since it is known that the complex NTSR trait in different weed species is multi-genic (Duhoux et al 2017b;Tétard-Jones et al, 2018), it is clear that a single GST cannot confer multiple resistance alone. However, GSTs would be prima candidates for having functional roles in NTSR, given their close association in counteracting multiple types of biotic and abiotic stress in plants (Cummins et al 1999).…”

“…To identify the full range of GST genes associated with NTSR in black-grass, the respective transcriptome contig sequences of NTSR (Peldon) as compared to the HS (Rothamsted) populations were exained, as generated by Ion-Torrent next generation sequencing (Tétard-Jones et al 2018). Using this approach, a total of 53 contigs corresponding to GST genes were identified, which were analyzed by Blast (BlastX) searches against the respective translated proteome database (Tétard-Jones et al 2018). This approach clustered the contigs to 15 distinct GSTs, which on online protein blast (BlastP) analysis, yielded eight GSTUs, six GSTFs and one GSTL gene (Supplemental Table S2).…”

“…Having established the inducibility of the GST superfamily in blackgrass at the transcriptome level, it was then of interest to investigate changes in their relative abundance in the proteome of NTSR versus HS plants. As described previously, the NTSR population were either derived from different geographical locations in the UK (Peldon, Essex and Oxford), or by repeated selection with the herbicides pendimethalin or fenoxaprop(Tétard-Jones et al 2018). Whereas 15 distinct GSTs showed induced transcriptional expression, the up-regulation of only four of these genes resulted in increased protein expression as determined by differential two-dimensional proteomics(Table 8).…”

Detection and characterization of resistance to acetolactate synthase inhibiting herbicides in Anisantha and Bromus species in the United Kingdom

“…In addition, grass weeds can develop nontarget site resistance (NTSR) to multiple herbicide chemistries through increased detoxification. This mechanism also is termed enhanced metabolic resistance (EMR) and has been recorded in many grass weeds . EMR is associated with the enhanced expression of herbicide detoxifying enzymes, notably cytochrome P450 monooxygenases (CYP450s) and glutathione transferases (GSTs) .…”