Comparative analysis of response to selection with three insecticides in the dengue mosquito Aedes aegypti using mRNA sequencing

Abstract

BackgroundMosquito control programmes using chemical insecticides are increasingly threatened by the development of resistance. Such resistance can be the consequence of changes in proteins targeted by insecticides (target site mediated resistance), increased insecticide biodegradation (metabolic resistance), altered transport, sequestration or other mechanisms. As opposed to target site resistance, other mechanisms are far from being fully understood. Indeed, insecticide selection often affects a large number of genes and various biological processes can hypothetically confer resistance. In this context, the aim of the present study was to use RNA sequencing (RNA-seq) for comparing transcription level and polymorphism variations associated with adaptation to chemical insecticides in the mosquito Aedes aegypti. Biological materials consisted of a parental susceptible strain together with three child strains selected across multiple generations with three insecticides from different classes: the pyrethroid permethrin, the neonicotinoid imidacloprid and the carbamate propoxur.ResultsAfter ten generations, insecticide-selected strains showed elevated resistance levels to the insecticides used for selection. RNA-seq data allowed detecting over 13,000 transcripts, of which 413 were differentially transcribed in insecticide-selected strains as compared to the susceptible strain. Among them, a significant enrichment of transcripts encoding cuticle proteins, transporters and enzymes was observed. Polymorphism analysis revealed over 2500 SNPs showing > 50% allele frequency variations in insecticide-selected strains as compared to the susceptible strain, affecting over 1000 transcripts. Comparing gene transcription and polymorphism patterns revealed marked differences among strains. While imidacloprid selection was linked to the over transcription of many genes, permethrin selection was rather linked to polymorphism variations. Focusing on detoxification enzymes revealed that permethrin selection strongly affected the polymorphism of several transcripts encoding cytochrome P450 monooxygenases likely involved in insecticide biodegradation.ConclusionsThe present study confirmed the power of RNA-seq for identifying concomitantly quantitative and qualitative transcriptome changes associated with insecticide resistance in mosquitoes. Our results suggest that transcriptome modifications can be selected rapidly by insecticides and affect multiple biological functions. Previously neglected by molecular screenings, polymorphism variations of detoxification enzymes may play an important role in the adaptive response of mosquitoes to insecticides.

Under-Expression of Chemosensory Genes in Domiciliary Bugs of the Chagas Disease Vector Triatoma brasiliensis

“…For example, over-transcription in a resistant strain of An . gambiae has suggested that the cuticle plays a role in response to selection pressures resulting from insecticide treatments [114]. In our study, cytochrome P450s, gluthatione S-transferases and cuticular proteins were all under-expressed in domiciliary bugs, which should be the most exposed to insecticide treatment.…”

Identifying genomic changes associated with insecticide resistance in the dengue mosquito Aedes aegypti by deep targeted sequencing

“…Most were previously found significantly overtranscribed in pyrethroid resistant Ae. aegypti populations according to data publicly available in the VectorBase expression browser (https://vectorbase.org, data sets from Strode et al 2008;Marcombe et al 2009;Poupardin et al 2012;David et al 2014). The majority of CNVs observed between resistant and susceptible populations were <2.5-fold, suggesting a predominance of duplications.…”

Proteomic analysis of Bayvarol® resistance mechanisms in the honey bee parasite Varroa destructor

“…These detoxification enzymes (e.g., microsomal p450 monooxygenases, glutathione-s-transerases and various esterases) may play an important role in the development of resistance in various other species such as Drosophila spp., Heliothis virescens, Heliocoverpa armigera, Anopholes spp. and Aedes aegypti (David et al, 2014;Scott, 1999). Pesticides can also lead to oxidative stress in the organism, and up-regulation of certain detoxification or stress-related proteins could provide a potential mechanism for protection (Abdollahi, Ranjbar, Shadnia, Nikfar, & Rezaie, 2004).…”