Culex pipiens pallens: Identification of genes differentially expressed in deltamethrin-resistant and -susceptible strains

Insecticide-resistance is a major obstacle to controlling insect vectors of microorganisms that cause human diseases. Identification of genes associated with resistance to insecticides has been a valuable tool for understanding mechanisms underlying resistance to commonly used insecticides such as deltamethrin. To identify such genes, we used suppression subtractive hybridization to obtain 809 differentially expressed clones in deltamethrin resistant versus susceptible laboratory strains of Culex pipiens pallens. Using cDNA microarrays and reverse Northern blots, a subset of 16 clones was confirmed to have greater than 3-fold difference in expression levels. Within this subset, we identified 2 clones uniquely expressed in the deltamethrin-resistant strain, eight clones exhibiting higher expression in the resistant strain and six in the susceptible strain. Of these 16 clones, 13 clones have sequence homology to known genes, such as ribosomal RNA, ribosome proteins, trypsin, and chymotrypsin-like proteins. Our data suggests resistance to deltamethrin may be a polygenic phenotype.