Genome-wide identification of neuropeptides from Plutella xylostella (Lepidoptera: Plutellidae) and elucidating the essential roles of adipokinetic hormone in lipid mobilisation and food intake.

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a major pest of cruciferous crops and has developed high levels of resistance to many widely used insecticides. Neuropeptides are involved in regulating essential insect biological processes, which could be considered potential target genes for pest control. In this study, a total of 45 neuropeptide precursor genes were identified in the genome of P. xylostella, including two adipokinetic hormone genes (PxAKH1 and PxAKH2). The qPCR analysis showed that PxAKH genes were highly expressed in third- and fourth-instar larvae and exhibited high expression levels in the fat body, head, and gut of P. xylostella larvae. Additionally, short-term starvation stimulated food consumption in P. xylostella, which was consistent with the significant induction of PxAKH1 within 6 h. Subsequently, RNA interference (RNAi) was utilised to investigate the functions of PxAKH1 in P. xylostella, and the injection of dsPxAKH1 significantly suppressed target gene expression, achieving a maximum silencing efficiency of 73.03%. Notably, knockdown of PxAKH1 increased triacylglycerol levels from 23.67 ± 0.56 mg/g in the dsGFP control to 25.84 ± 0.64 mg/g and enhanced lipid storage, while markedly reducing food intake from 221.33 ± 9.10 mm2 to 123.33 ± 18.80 mm2 in P. xylostella larvae. In summary, these findings demonstrate that PxAKH1 plays a critical role in regulating lipid mobilisation and food intake in P. xylostella, indicating its potential as an RNAi-based target for pest control.