Characteristics of the Insulin-like Peptide Genes and Their Roles in the Ovarian Development of Zeugodacus cucurbitae (Coquillett)

The melon fly Zeugodacus cucurbitae (Coquillett) is a globally invasive pest responsible for substantial economic losses in the fruit and vegetable industries. Insulin-like peptides (ILPs) are evolutionarily conserved neuropeptides that play a crucial role in insect reproduction. In this study, six ZcILPs from the melon fly, designated as ZcILP1–6, were cloned. Phylogenetic analysis demonstrated a strong orthologous link with Dipteran ILPs. Spatiotemporal expression profiling revealed that ZcILP1 and ZcILP3 exhibit preferential enrichment in the adult female fat body, with their expression specifically and significantly upregulated in 5-day-old individuals. Their expression decreased 12, 24, and 48 h post-starvation and increased upon re-feeding. Silencing ZcILP1 and ZcILP3 resulted in reduced ovarian size by 51.42% and 69.17%, respectively. Furthermore, silencing ZcILP1 or ZcILP3 significantly decreased the transcriptional levels of genes downstream of the insulin signaling pathway (ISP), notably the target of rapamycin (ZcTOR) and Forkhead box O (ZcFOXO). Concurrently, the expression of Vitellogenin (ZcVg), a gene associated with reproduction, was significantly downregulated. These findings indicate that ZcILP1 and ZcILP3 regulate ZcVgs expression and ovarian development through ISP, suggesting them as potential targets for green control of Z. cucurbitae.