Cap 'n' collar C regulates genes responsible for imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata exposed to Imidacloprid for multiple generations became resistant to this insecticide. These beetles display a coordinated transcriptional response to insecticides by inducing detoxification enzymes. Our previous studies showed that xenobiotic transcription factor, cap ‘n’ collar isoform C (CncC) regulates the expression of multiple cytochrome P450 genes, which play an important role in resistance to plant allelochemicals and insecticides. In this study, we sought to obtain a comprehensive picture of the genes regulated by CncC in Imidacloprid resistant CPB. We performed sequencing of mRNA isolated from Imidacloprid-resistant CPB injected with dsRNA targeting CncC or green fluorescent protein (GFP, control). Comparative transcriptome analysis showed that CncC regulates the expression of 1,798 genes, out of which 1,499 genes were downregulated and 349 genes were upregulated (at a p-value <0.05 and ≥4-fold difference) in the CncC knockdown beetles. We performed quantitative real-time PCR to verify the reduction in the expression of 20 genes including those coding for detoxification enzymes. Based on the RNA sequencing (BLAST, GO enrichment and KEGG pathway) analyses, we identified 21 genes code for major detoxification enzymes that include twelve P450s, two GSTs, two esterases and five ABC transporters. Moreover, three genes coding for ABC transporters are induced in resistant beetles and knockdown of these genes simultaneously or individually caused an increase in Imidacloprid induced mortality suggesting that these transporters may contribute to insecticide resistance.