Developmental control of Helicoverpa armigera by ingestion of bacteria expressing dsRNA targeting an arginine kinase gene

Abstract

ABSTRACTCotton bollworm (Helicoverpa armigera) is a polyphagous pest that causes agricultural and commercial losses in many parts of the world. These losses are compounded by insecticide abuse, which leads to insecticide resistance as well as environmental and food pollution. RNA interference (RNAi) is a powerful tool used in gene functional research and RNAi-based pest control. In this study, arginine kinase (AK) of cotton bollworm was selected as the target gene, as it plays a critical role in cellular energy metabolism in invertebrates. Two fragments of the H. armigera AK gene (HarmAK) were cloned into the L4440 vector to express double-stranded RNA (dsRNA) in Escherichia coli (HT115). The effects of different factors on dsRNA stability and the effect of silencing HarmAK on cotton bollworm were subsequently investigated. Both AK gene and protein expression levels were significantly inhibited in larvae, and the peak cumulative mortality rate of 44.44% was recorded on day 5, after 2nd instar larvae were exposed to the artificial diet coated with the engineered bacteria. The two dsRNAs (dsAK1 and dsAK2) also caused drastic reductions in body weight (38.43% and 17.37%, respectively), body length (26.73% and 11.23%, respectively) and pupation rate (48.89% and 42.95%, respectively) compared to the control on day 5. The development and morphology of the larvae, pupae and adults that fed on the dsAK1 and dsAK2 bacteria were significantly impaired, while the control was not. Thus, AK is a potential target gene for RNAi-mediated cotton bollworm control.