Abstract
BackgroundContinuous and excessive application of insecticides has resulted in the rapid development of insecticide resistance in several mosquito species, including Culex pipiens pallens. Previous studies in our laboratory found that arrestin gene expression was higher in the deltamethrin-resistant (DR) strain than in the deltamethrin-susceptible (DS) strain of Cx. pipiens pallens. Similarly, other studies reported that arrestin was highly expressed in permethrin-resistant Cx. quinquefasciatus and in dichlorodiphenyltrichloroethane (DDT)-resistant Drosophila melanogaster.MethodsFull-length cDNAs of an arrestin gene were cloned from Cx. pipiens pallens via polymerase chain reaction (PCR) and rapid amplification of cDNA end (RACE). The mRNA levels of the arrestin gene in the whole life cycle of DR and DS strains of Cx. pipiens pallens were investigated via quantitative real-time PCR. In addition, the relationship between arrestin and deltamethrin (DM) resistance were identified using genetic overexpression strategies and arrestin RNAi in mosquito cells. Cell viability was analyzed with cholecystokinin octapeptide after DM treatment. Moreover, the mRNA levels of cytochrome P450 6A1 (CYP6A1) and opsin in the transfected cells and controls were analyzed.ResultsComplete arrestin gene sequence was cloned and expressed throughout the life cycle of Cx. pipiens pallens. Moreover, arrestin was significantly upregulated in the DR strain, compared with that in the DS strain at the egg, pupae, and adult stages. Arrestin overexpression comparably increased the mosquito cell viability, whereas arrestin knockdown by siRNA decreased mosquito cell viability with deltamethrin (DM) treatment. Meanwhile, the mRNA levels of CYP6A1 and opsin were upregulated in mosquito cells transfected with arrestin and downregulated in mosquito cells with arrestin knockdown.ConclusionThis study presented the first evidence that arrestin might be associated with insecticide resistance in Cx. pipiens pallens.
Highlights
Continuous and excessive application of insecticides has resulted in the rapid development of insecticide resistance in several mosquito species, including Culex pipiens pallens
The same-frame stop codon TAA was found at 162–164 upstream of start codon ATG, indicating that the sequence is the full length of arrestin mRNA (Additional file 2: Figure S2)
The phylogenetic relationships of arrestin between Cx. pipiens pallens and other species showed that arrestin from Cx. pipiens pallens has the highest homology with Cx. quinquefasciatus and Anopheles gambiae using the neighbor-joining method (Additional file 4: Figure S4)
Summary
Continuous and excessive application of insecticides has resulted in the rapid development of insecticide resistance in several mosquito species, including Culex pipiens pallens. Previous studies in our laboratory found that arrestin gene expression was higher in the deltamethrin-resistant (DR) strain than in the deltamethrinsusceptible (DS) strain of Cx. pipiens pallens. Deltamethrin (DM), an important synthetic pyrethroid insecticide that kills insects by stimulating their nervous system (a similar mode of action to DDT), is widely used in bed net impregnation and indoor residual spray to help control the transmission of insect-borne diseases [12]. Under natural selection, continuous and excessive application of DM and other synthetic pyrethroids have resulted in the rapid development of insecticide resistance in several species, including Cx. pipiens pallens. Insecticide resistance has become a major obstacle in the control of vector-borne diseases and a cause for a major public health concern [13]. Other genes contributing to the resistance are yet to be identified
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