Effects of different insecticides on transcripts of key genes in CncC pathway and detoxification genes in Helicoverpa armigera

Regulation of CncC in insecticide-induced expression of cytochrome P450 CYP9A14 and CYP6AE11 in Helicoverpa armigera

The expression of many detoxification genes can be regulated by CncC pathway and contributes to insecticide tolerance in insects. Our previous study has demonstrated that the transcripts of CncC and cytochrome P450s (CYP9A14, CYP6AE11) were significantly up-regulated after different insecticides treatment in Helicoverpa armigera. Further study indicated that H2O2, GSH, and MDA contents and antioxidant enzyme activities of H. armigera were enhanced after chlorantraniliprole, cyantraniliprole, indoxacarb, and spinosad exposure. Silencing CncC by RNA interference significantly down-regulated the expression levels of CYP9A14 and CYP6AE11, and increased the susceptibility of dsRNA-injected larvae to λ-cyhalothrin, chlorantraniliprole, and cyantraniliprole. On the contrary, applying CncC agonist curcumin on H. armigera induced the expression of CYP9A14 and CYP6AE11, and enhanced the tolerance of H. armigera to insecticides. Treatment of ROS scavenger N-acetylcysteine on H. armigera reduced the H2O2 content and antioxidant enzyme activities, suppressed the transcripts of CncC, CYP9A14, and CYP6AE11, and decreased the larval tolerance to insecticides. These results demonstrated that the induced-expression of CYP9A14 and CYP6AE11 related with insecticides tolerance in H. armigera was regulated by CncC, which may be activated by ROS generated by insecticides. This study will help to better understand the underlying regulation mechanisms of CncC pathway in H. armigera tolerance to insecticides.

Transcription factors, cap 'n' collar isoform C regulates the expression of CYP450 genes involving in insecticides susceptibility in Locusta migratoria

BACKGROUND

The cap 'n' collar (Cnc) belongs to the Basic Leucine Zipper (bZIP) transcription factor super family. Cap 'n' collar isoform C (CncC) is highly conserved in the animal kingdom. CncC contributes to the regulation of growth, development, and aging and takes part in the maintenance of homeostasis and the defense against endogenous and environmental stress. Insect CncC participates in the regulation of various kinds of stress-responsive genes and is involved in the development of insecticide resistance.

RESULTS

In this study, one full-length CncC sequence of Locusta migratoria was identified and characterized. Upon RNAi silencing of LmCncC, insecticide bioassays showed that LmCncC played an essential role in deltamethrin and imidacloprid susceptibility. To fully investigate the downstream genes regulated by LmCncC and further identify the LmCncC-regulated genes involved in deltamethrin and imidacloprid susceptibility, a comparative transcriptome was constructed. Thirty-five up-regulated genes and 73 down-regulated genes were screened from dsLmCncC-knockdown individuals. We selected 22 LmCncC-regulated genes and verified their gene expression levels using RT-qPCR. Finally, six LmCYP450 genes belonging to the CYP6 family were selected as candidate detoxification genes, and LmCYP6FD1 and LmCYP6FE1 were further validated as detoxification genes of insecticides via RNAi, insecticide bioassays, and metabolite identification.

CONCLUSIONS

Our data suggest that the locust CncC gene is associated with deltamethrin and imidacloprid susceptibility via the regulation of LmCYP6FD1 and LmCYP6FE1, respectively.