Bacterial Rdl2 dsRNA increased the insecticidal activity of GABAR blockers and allosteric modulators against Plutella xylostella

BACKGROUND The application of RNAi to control pests has attracted the attention of researchers. Our results indicated that knockout of PxRdl2 can decrease resistance to fipronil in Plutella xylostella , providing a suitable target gene for RNAi-based pest control. RESULTS The differences in the sensitivity of two established homozygous knockout strains of P. xylostella . ( Rdl1 KO and Rdl2 KO) and susceptible P. xylostella to a series of compounds were evaluated. Quinazolines and isoxazolines both showed stronger efficacy in the Rdl2 KO strain. Therefore, we proposed a method based on the knockdown of the P. xylostella Rdl2 gene as a tactic to enhance the toxicity of quinazolines and isoxazolines. To reduce costs and protect dsRNA against degradation, we applied a bacterial expression system using the L4440 vector to express PxRdl2 dsRNA in HT115 Escherichia coli . Transformed bacteria (dsRNA-Bac) fed through leaves combined with quinazoline and isoxazolines proved to be more effective in both the susceptible and fipronil-resistant P. xylostella . CONCLUSION Our results provide a strategy for the development of novel insecticide spray formulations containing dsRNA-Bac, which synergize with insecticide toxins by suppressing PxRdl2 , reducing the use of pesticides in the field. ### Competing Interest Statement The authors have declared no competing interest.