Gene silencing of CYP450 enzymes using RNA interference (RNAi) restores insecticide susceptibility in whitefly populations from Georgia, USA

The whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a major pest of vegetable and agronomic crops in Georgia. Neonicotinoids and diamides are commonly used to control whiteflies in the state. Numerous laboratory and field studies have indicated that whiteflies face a significant risk of developing resistance to these insecticides. Overexpression of multiple cytochrome P450 genes is responsible for a high level of insecticide resistance. This study focuses on the MEAM1 B-biotype, an invasive whitefly species in Georgia, to examine potential resistance mechanisms mediated by CYP450 enzymes. The activity of the P450 enzyme was higher in both selected strains of imidacloprid and cyantraniliprole than in the susceptible strain. In the synergism test, piperonyl butoxide (PBO) significantly enhanced the control efficacy of both insecticides against the resistant strain. Using qPCR analysis, the mRNA expression levels of CYP6CM1 and CYP6DW2 were upregulated following insecticide exposure for both insecticide-resistant populations compared to susceptible strains. Notably, only the cyantraniliprole-resistant strain exhibits overexpression of CYP6CX2 and CYP6CX3 among the studied CYP450 genes. Among the nine tested genes, CYP6CM1 showed the highest expression level, and sequence analysis did not reveal any functional mutations in CYP6CM1. RNA interference (RNAi) targeting four selected CYP450 genes effectively suppressed each mRNA level by using gene-specific double-stranded RNA (dsRNA). Feeding the resistant population with specific dsRNA targeting CYP450 significantly increased adult mortality. These findings suggest that multiple CYP450 genes are involved in insecticide resistance and could be targeted for RNAi-mediated pest management of B. tabaci.
Keywords: Whitefly, Insecticide Resistance, Cytochrome P450, RNAi.