High-resolution genetic mapping reveals cis-regulatory and copy number variation in loci associated with cytochrome P450-mediated detoxification in a generalist arthropod pest

Abstract

Chemical control strategies are driving the evolution of pesticide resistance in pest populations. Understanding the genetic mechanisms of these evolutionary processes is of crucial importance to develop sustainable resistance management strategies. The acaricide pyflubumide is one of the most recently developed mitochondrial complex II inhibitors with a new mode of action that specifically targets spider mite pests. In this study, we characterize the molecular basis of pyflubumide resistance in a highly resistant population of the spider mite Tetranychus urticae. Classical genetic crosses indicated that pyflubumide resistance was incompletely recessive and controlled by more than one gene. To identify resistance loci, we crossed the resistant population to a highly susceptible T. urticae inbred strain and propagated resulting populations with and without pyflubumide exposure for multiple generations in an experimental evolution set-up. High-resolution genetic mapping by a bulked segregant analysis approach led to the identification of three quantitative trait loci (QTL) linked to pyflubumide resistance. Two QTLs were found on the first chromosome and centered on the cytochrome P450 CYP392A16 and a cluster of CYP392E6-8 genes. Comparative transcriptomics revealed a consistent overexpression of CYP392A16 and CYP392E8 in the experimental populations that were selected for pyflubumide resistance. We further corroborated the involvement of CYP392A16 in resistance by in vitro functional expression and metabolism studies. Collectively, these experiments uncovered that CYP392A16 N-demethylates the toxic carboxamide form of pyflubumide to a non-toxic compound. A third QTL coincided with cytochrome P450 reductase (CPR), a vital component of cytochrome P450 metabolism. We show here that the resistant population harbors three gene copies of CPR and that this copy number variation is associated with higher mRNA abundance. Together, we provide evidence for detoxification of pyflubumide by cytochrome P450s that is likely synergized by gene amplification of CPR.

Abundant trans-driven variation in detoxification gene expression in the extreme generalist herbivore Tetranychus urticae

“…urticae strains [51][52][53][54]. Further, more than 98% of SNP sites were fixed in each of the five strains, confirming earlier reports that ~7 generations of inbreeding in this haplodiploid species results in isogenic (or nearly isogenic) strains [52].…”

MAPK-mediated transcription factor GATAd contributes to Cry1Ac resistance in diamondback moth by reducing PxmALP expression

“…The overexpression of detoxifying enzyme genes associated with metabolic resistance can be achieved through changes in cis-acting promoter regions and/or trans-acting regulatory loci [22,23]. With advances in bioinformatics, the causal genetic variants that promote the development of quantitative traits, such as pesticide resistance, are now being illustrated in arthropod pests [24].…”

Susceptibility to Acaricides and the Frequencies of Point Mutations in Etoxazole- and Pyridaben-Resistant Strains and Field Populations of the Two-Spotted Spider Mite, Tetranychus urticae (Acari: Tetranychidae)

“…P450s and glutathione- S -transferases have been related to the acaricidal effect of cyflumetofen [ 33 , 38 ]. Pyflubumide is classified in the new subgroup 25B (carboxanilide) in the IRAC (Insecticide Resistance Action Committee) MoA classification as a novel inhibitor of mitochondrial complex II on the respiratory chain and has a similar mechanism to cyenopyrafen and cyflumetofen, so resistance to this compound may have developed via the same factors [ 39 , 40 ]. Spirodiclofen, spiromesifen, and spirotetramat have sterility effects on adult females and ovicidal effects on eggs but do not have a control effect on adults [ 41 ].…”