Cyantraniliprole and thiamethoxam treatments modulate expression of cytochrome P450s and glutathione S-transferases in the Colorado potato beetle

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) can cause important damages to potato crops worldwide. While various strategies have been undertaken to mitigate its impact, such as the use of insecticides including neonicotinoids and ryanoids, this insect often develops resistance against these compounds. Characterizing the molecular changes resulting from L. decemlineata exposure to insecticides is necessary to develop novel and targeted approaches aimed at this pest. This project thus assesses the expression of select transcripts coding for proteins associated with insecticide resistance. Quantification of seven transcripts coding for cytochrome P450s and three transcripts coding for glutathione S-transferases was performed using qRT-PCR in adult L. decemlineata exposed to low and high doses of cyantraniliprole or thiamethoxam for different time durations. Exposure to cyantraniliprole resulted in modulation of transcripts coding for CYP4c1, CYP4g15, CYP6a23 and CYP9e2 in treated insects. Significant changes were also observed for CYP4g15, CYP6a23, CYP9e2, CYP12a5 and GST-1-Like transcripts in insects exposed to thiamethoxam. RNAi-based reduction of CYP6a13 and CYP12a5 transcript levels in L. decemlineata injected with dsRNA was associated with significant down-regulation of transcripts seven days post-injection. Injected insects were also treated with an insecticide of interest and survival assessed before and after treatments to characterize the potential impact of these transcripts on L. decemlineata response towards this compound. Overall, these results highlight the modulation of transcripts with potential relevance for cyantraniliprole and thiamethoxam response in L. decemlineata and reveal targets that warrant further investigation in the development of dsRNA-based approaches for this pest.