Contrasting roles of cytochrome P450s in amitraz and chlorfenapyr resistance in the crop pest <i>Tetranychus urticae</i>

Vandenhole et al. (2023) used transcriptomic and bulked segregant analysis (BSA) to reveal contrasting roles of cytochrome P450s in amitraz and chlorfenapyr resistance in the crop pest Tetranychus urticae. The molecular mechanisms of amitraz and chlorfenapyr resistance remain only poorly understood for major agricultural pests and vectors of human diseases. This study focusses on a multi-resistant field strain of the crop pest Tetranychus urticae, which could be readily selected in the laboratory to high levels of amitraz and chlorfenapyr resistance. Toxicity experiments using tralopyril, the active toxophore of chlorfenapyr, suggested decreased activation as a likely mechanism underlying resistance. Starting from the same parental strain, transcriptome profiling revealed that a cluster of detoxifying genes was upregulated after amitraz selection, but unexpectedly downregulated after chlorfenapyr selection. Further functional validation associated the upregulation of CYP392A16 with amitraz metabolism and the downregulation of CYP392D8 with reduced activation of chlorfenapyr to tralopyril. Genetic mapping (QTL analysis by BSA) was conducted in an attempt to unravel the genetic mechanisms of expression variation and resistance. This revealed that chlorfenapyr resistance was associated with a single QTL, while 3 QTLs were uncovered for amitraz resistance. Together with the observed contrasting gene expression patterns, we argue that transcriptional regulators most likely underly the distinct expression profiles associated with resistance, but these await further functional validation. The Supplementary Data for Vandenhole et al. (2023) comprises: Data S1: genomic VCF (gzipped) used as input for the RUN_BSA1.02.py script available at https://github.com/rmclarklab/BSA (Kurlovs et al. 2019, PMID: 31499416); Data S2: output of the RUN_BSA1.02.py script for the amitraz BSA; Data S3: output of the RUN_BSA1.02.py script for the chlorfenapyr BSA; Data S4: raw read counts of all RNAseq data generated in this study;