Pyrethroid-resistance is modulated by miR-92a by targeting CpCPR4 in Culex pipiens pallens

The wide use of pyrethroids has resulted in the emergence and spread of resistance in mosquito populations, which represent a major obstacle in the struggle against vector-borne diseases. Resistance to pyrethroids is a complex genetic phenomenon attributed by polygenetic inheritance. We previously have sequenced and analyzed the miRNA profiles of Culex pipiens pallens. MiR-92a was found to be overexpressed in a deltamethrin-resistant (DR) strain. The association of miR-92a with pyrethroid-resistance was investigated by quantitative reverse transcription PCR (qRT-PCR). Expression levels of miR-92a were 2.72-fold higher in the DR strain than in the deltamethrin-susceptible (DS) strain. Bioinformatic analysis suggested that CpCPR4, a mosquito cuticle gene, is the target of miR-92a. Dual luciferase reporter assays further confirmed that CpCPR4 is modulated by miR-92a through binding to a specific target site in the 3' untranslated region (3' UTR). Microinjection of the miR-92a inhibitor upregulated CpCPR4 expression levels, leading to an increase in the susceptibility of the DR strain in the Centers for Disease Control and Prevention (CDC) bottle bioassay (a surveillance tool for detecting resistance to insecticides in vector populations). Taken together, our findings indicate that miR-92a regulates pyrethroid-resistance through its interaction with CpCPR4.