The cuticle proteins: a putative role for deltamethrin resistance in Culex pipiens pallens

Insecticide resistance has been a major public health challenge. It is impendent to study the mechanism on insecticide resistance. In our previous study, 14 differentially accumulated insect cuticle proteins (ICPs) based on insecticide resistance proteomes and transcriptomes were found in the deltamethrin-resistant (DR) and -susceptible (DS) strains of Culex pipiens pallens. To investigate if these ICPs are associated with deltamethrin resistance, different transcriptional levels of the 14 ICPs were detected in the DS and DR strains from laboratory and field populations by using quantitative real-time polymerase chain reaction (qRT-PCR). The expression levels of the 14 ICPs were also measured after short-term exposure of the DS strain to deltamethrin. The full-length complementary DNA (cDNA) of CpCPLCG5 gene, which encodes one of the 14 ICPs, was cloned from Cx. pipiens pallens. Homology analysis and phylogenetic analysis were carried out with some other insects. Furthermore, small interfering RNA (siRNA) was used to knockdown the expression level of CpCPLCG5 gene for characterizing its contribution to deltamethrin resistance. The results showed that the expression level of CpCPLCG5 gene was higher in DR strain than in DS strain both in laboratory and field populations while the other 13 ICPs were downregulated. The full-length cDNA of CpCPLCG5 gene was 732 bp, with the ORF of 390 bp and deduced 129 amino acids (GenBank/KF723314,2013). Knockdown of CpCPLCG5 gene increased the susceptibility of the DR strain while the expression level of the other 13 ICPs elevated. Our findings indicate that the cuticle proteins are associated with deltamethrin resistance in Cx. pipiens pallens.