Suppression of Adipokinetic hormones enhances Ascovirus HvAV-3h killing speed in Helicoverpa armigera

Abstract

The emergence of pesticide resistance in Helicoverpa armigera and other pests represents a challenge, necessitating continued development of innovative insecticides. Ascoviruses are a potential insecticide for H. armigera. These double-stranded DNA viruses cause cell death and lethal disease in infected larvae. However, this disease is chronic and prolongs the lifespan of the infected larvae by several weeks. The slow killing speed limits the success of these pathogens in the insecticidal market. Here, we demonstrate that the dsRNA silencing of H. armigera neuropeptide Adipokinetic Hormones (HaAKH) accelerates the killing speed of Heliothis virescens ascovirus 3h (HvAV-3h) against the third-instar larvae of H. armigera. The LT50 was reduced to 3.96 days in larvae with silenced HaAKH1 and 4.7 days in those with silenced HaAKH3. Moreover, the histopathological examinations revealed the destruction of the host's fat body and epidermal tissue shrinkage after HaAKH silencing during HvAV-3h infection. Examining detoxification and antioxidant enzyme activity in HvAV-3h infected larvae showed reduced detoxification mechanisms after HaAKH gene silencing. Furthermore, the silencing of HaAKH resulted in an overall reduction in the fold changes of proline dehydrogenase. In conclusion, this study demonstrates that the ascovirus killing speed can be accelerated by interfering with the host neuropeptide-related gene expression. Moreover, the silencing of H. armigera HaAKH1 and HaAKH3 decreased the antiviral immunity against HvAV-3h.