AKH/AKHR signalling system induced antioxidant response mediated by entomopathogenic fungi in Nilaparvata lugens (Stål)

The brown planthopper Nilaparvata lugens is one of the most economically important rice crop pests in Asia. Entomopathogenic fungi (EPF) have been developed as a biological control of N. lugens. Insect adipokinetic hormones (AKHs) are pleiotropic hormones that play a protective role in response to oxidative stress. However, the role of AKH in the anti-oxidative response of N. lugens to EPFs (Metarhizium anisopliae and Beauveria bassiana) infection remains largely unexplored. In this study, the results of relative enzyme activities and expression levels of antioxidant enzymes demonstrated the response of the antioxidant system of N. lugens to EPF infection. Additionally, the expression of AKH/adipokinetic hormone receptor (AKHR) also induced responding to the infection of EPF in N. lugens. Silencing NlAKH or NlAKHR significantly increased mortality in nymphs treated with fungi compared with controls, whereas the injection of AKH peptide decreased mortality. Further research indicated that the AKH/AKHR system positively influenced antioxidant enzymes, potentially involving the transcription factors forkhead-box O and Cap’ n’ collar C. These findings provide an important theoretical basis for developing new pest control agents targeting the neuropeptide AKH and offer new insights for mitigating brown planthopper resistance and promoting green control strategies.