Insights into DDT Resistance from the Drosophila melanogaster Genetic Reference Panel

Abstract

Insecticide resistance is considered a classic model of microevolution, where a strong selective agent is applied to a large natural population, resulting in a change in frequency of alleles that confer resistance. While many insecticide resistance variants have been characterized at the gene level, they are typically single genes of large effect identified in highly resistant pest species. In contrast, multiple variants have been implicated in DDT resistance in Drosophila melanogaster; however, only the Cyp6g1 locus has previously been shown to be relevant to field populations. Here we use genome-wide association studies (GWAS) to identify DDT-associated polygenes and use selective sweep analyses to assess their adaptive significance. We identify and verify two candidate DDT resistance loci. A largely uncharacterized gene, CG10737, has a function in muscles that ameliorates the effects of DDT, while a putative detoxifying P450, Cyp6w1, shows compelling evidence of positive selection.

Identification of a genetic network for an ecologically relevant behavioural phenotype in Drosophila melanogaster

“…The broad‐sense heritability ( H 2 ) was estimated by determining the proportion of total variance in the mean strain height measurements compared to the average within each strain (Schmidt et al, ). The narrow‐sense heritability ( h 2 ) was estimated here as “SNP heritability” (Wray et al, ), that is, the estimate of the proportion of phenotypic variance explained by all available SNPs (or genetic variants) in the DGRP stocks.…”

“…The broad‐sense heritability ( H 2 ) was estimated with the variance components of a linear model of the form: Phenotype = Population mean + Line effect + error (Schmidt et al, ). Total phenotypic variance was estimated as Genetic Variance + Environmental Variance, and the H 2 was thus estimated as G v /( G v + E v ).…”

“…The broad-sense heritability (H 2 ) was estimated with the variance components of a linear model of the form: Phenotype = Population mean + Line effect + error (Schmidt et al, 2017). Total phenotypic variance was estimated as Genetic Variance + Environmental Variance, and the H 2 was thus estimated as The narrow-sense heritability was estimated as the proportion of variance in a phenotype explained by all available genetic variants used for mapping, an estimate that is often called "SNP heritability" (Visscher, Hill, & Wray, 2008;Wray et al, 2013).…”

“…The broad-sense heritability (H 2 ) was estimated by determining the proportion of total variance in the mean strain height measurements compared to the average within each strain (Schmidt et al, 2017).…”

Comparative CYP‐omic analysis between the DDT‐susceptible and ‐resistant Drosophila melanogaster strains 91‐C and 91‐R

“…Additionally, an I115L alteration in the SRS 1 region of CYP6B1 is involved in substrate turnover in Papilio polyxenes . Recent work by Schmidt et al . demonstrated that transgenic overexpression of the CYP6W1_Ala370 allele increased DDT resistance relative to CYP6W1_Val370 and CYP6W1_Gly370.…”