Quantitative Trait Loci Mapping of Genome Regions Controlling Permethrin Resistance in the Mosquito Aedes aegypti

Abstract

The mosquito Aedes aegypti is the principal vector of dengue and yellow fever flaviviruses. Permethrin is an insecticide used to suppress Ae. aegypti adult populations but metabolic and target site resistance to pyrethroids has evolved in many locations worldwide. Quantitative trait loci (QTL) controlling permethrin survival in Ae. aegypti were mapped in an F 3 advanced intercross line. Parents came from a collection of mosquitoes from Isla Mujeres, México, that had been selected for permethrin resistance for two generations and a reference permethrin-susceptible strain originally from New Orleans. Following a 1-hr permethrin exposure, 439 F 3 adult mosquitoes were phenotyped as knockdown resistant, knocked down/recovered, or dead. For QTL mapping, single nucleotide polymorphisms (SNPs) were identified at 22 loci with potential antixenobiotic activity including genes encoding cytochrome P450s (CYP), esterases (EST), or glutathione transferases (GST) and at 12 previously mapped loci. Seven antixenobiotic genes mapped to chromosome I, six to chromosome II, and nine to chromosome III. Two QTL of major effect were detected on chromosome III. One corresponds with a SNP previously associated with permethrin resistance in the para sodium channel gene and the second with the CCEunk7o esterase marker. Additional QTL but of relatively minor effect were also found. These included two sex-linked QTL on chromosome I affecting knockdown and recovery and a QTL affecting survival and recovery. On chromosome II, one QTL affecting survival and a second affecting recovery were detected. The patterns confirm that mutations in the para gene cause target-site insensitivity and are the major source of permethrin resistance but that other genes dispersed throughout the genome contribute to recovery and survival of mosquitoes following permethrin exposure.

Local Evolution of Pyrethroid Resistance Offsets Gene Flow Among Aedes aegypti Collections in Yucatan State, Mexico

“…The excess of heterozygotes at CCE1C might also be associated with duplication. However, in earlier studies we found that the segregation of alleles at the para locus 12 and three different CCE-C genes fit a single gene model. 19 Linkage disequilibrium among loci.…”

“…The SNP identification, allele-specific polymerase chain reaction (PCR), melting curve conditions, and genotype readings followed published procedures. 11,12,21,22 Table 2 lists the names of the SNP markers, their VectorBase identification numbers, physical or genetic location in the genome (if known) and the primer sequences used for allele-specific PCR. We obtained SNP genotypes at 13 SNP loci in each mosquito.…”

“…These include I1,016 and C1,534 in para and two cytochrome P 450 genes, CYP9J32 and CYP9J29 previously associated with permethrin resistance in a QTL mapping study 12 and in a microarray analysis. 13 Moreover, CYP9J32 has exhibited pyrethroid metabolizing activity 14 and was also overexpressed in Mexican mosquito lines selected with temephos alongside a carboxyl/esterase gene CCE1C.…”

“…E-mail: ksaavedr@colostate.edu genetic and mapping studies. 12,[16][17][18][19] Alleles at these 13 loci were compared among 27 collections of Ae. aegypti originating from eight different communities in Yucatan State.…”

Assessing Insecticide Susceptibility of LaboratoryLutzomyia longipalpisandPhlebotomus papatasiSand Flies (Diptera: Psychodidae: Phlebotominae)

“…A cotton ball saturated with 30% sugar-water was placed on the top of each container as an energy/water source. Using procedures established for mosquitoes, sand flies were held in these containers for 24 h prior to mortality being recorded (Saavedra-Rodriguez et al 2008). Mortality was scored as a complete cessation of movement (Perea et al 2009).…”