title: Comparative analysis of response to selection with three insecticides in the dengue mosquito Aedes aegypti using mRNA sequencing.
abstract: BACKGROUND
  Mosquito 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.
  
  
  RESULTS
  After 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Laboratoire d'Ecologie Alpine (LECA), UMR CNRS 5553, Grenoble, France. jean-philippe.david@ujf-grenoble.fr.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: David
authors.forename: Frédéric
authors.initials: F
authors.lastname: Faucon
authors.forename: Alexia
authors.initials: A
authors.lastname: Chandor-Proust
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Poupardin
authors.forename: Muhammad Asam
authors.initials: MA
authors.lastname: Riaz
authors.forename: Aurélie
authors.initials: A
authors.lastname: Bonin
authors.forename: Vincent
authors.initials: V
authors.lastname: Navratil
authors.forename: Stéphane
authors.initials: S
authors.lastname: Reynaud
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000235:genetics*; D000818:Animals; D002874:Chromosome Mapping; D016000:Cluster Analysis; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D016678:Genome; D059014:High-Throughput Nucleotide Sequencing; D008658:Inactivation, Metabolic / Q000235:genetics; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D051379:Mice; D058977:Molecular Sequence Annotation; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000235:genetics*; D017423:Sequence Analysis, RNA; D059467:Transcriptome
chemical_list: D007306:Insecticides; D012333:RNA, Messenger