Transcriptomic and proteomic analysis of pyrethroid resistance in the CKR strain of Aedes aegypti

Abstract

Aedes aegypti is an important vector of human viral diseases. This mosquito is distributed globally and thrives in urban environments, making it a serious risk to human health. Pyrethroid insecticides have been the mainstay for control of adult A. aegypti for decades, but resistance has evolved, making control problematic in some areas. One major mechanism of pyrethroid resistance is detoxification by cytochrome P450 monooxygenases (CYPs), commonly associated with the overexpression of one or more CYPs. Unfortunately, the molecular basis underlying this mechanism remains unknown. We used a combination of RNA-seq and proteomic analysis to evaluate the molecular basis of pyrethroid resistance in the highly resistant CKR strain of A. aegypti. The CKR strain has the resistance mechanisms from the well-studied Singapore (SP) strain introgressed into the susceptible Rockefeller (ROCK) strain genome. The RNA-seq and proteomics data were complimentary; each offering insights that the other technique did not provide. However, transcriptomic results did not quantitatively mirror results of the proteomics. There were 10 CYPs which had increased expression of both transcripts and proteins. These CYPs appeared to be largely trans-regulated, except for some CYPs for which we could not rule out gene duplication. We identified 65 genes and lncRNAs as potentially being responsible for elevating the expression of CYPs in CKR. Resistance was associated with multiple loci on chromosome 1 and at least one locus on chromosome 3. We also identified five CYPs that were overexpressed only as proteins, suggesting that stabilization of CYP proteins could be a mechanism of resistance. Future studies to increase the resolution of the resistance loci, and to examine the candidate genes and lncRNAs identified here will greatly enhance our understanding of CYP-mediated resistance in A. aegypti. Author summary Aedes aegypti is an important vector of human viral diseases and is commonly controlled using pyrethroid insecticides. This has led to the evolution of insecticide resistance in this mosquito via two main mechanisms: increased detoxification of pyrethroids mediated by cytochrome P450 proteins (CYPs) and mutations in the voltage sensitive sodium channel (Vssc, gene for the target site of pyrethroids). While much is known about the Vssc mutations, the mutation(s) causing the CYP-mediated resistance has been elusive. We used a combined transcriptomic and proteomic approach to try to identify the molecular basis of CYP-mediated resistance in the highly resistant CKR strain. We identified CYPs that were overexpressed in the CKR strain, and for most of these the increased expression was due to a trans-acting factor. We identified 65 transcription factors or long non-coding RNAs (lncRNAs) that may play a role in the increased expression of these CYPs. We also found evidence that stabilization of CYP proteins could be a mechanism of resistance.