The Function of C-Terminal Pentapeptide in Allatostatin Type-C: Regulating Growth and Development by Affecting Juvenile Hormone Biosynthesis in Ostrinia furnacalis

Abstract Allatostatin Type-C (AstC) is an insect neuropeptide involved in developmental regulation, but whether its conserved C-terminal pentapeptide, PISCF, remains bioactive as an isolated fragment is unclear. Herein, the synthetic PISCF was evaluated on the Asian corn borer, Ostrinia furnacalis, with AstC as a reference. Under sublethal exposure, PISCF suppressed larval growth, reduced relative consumption rate by 47.8–62.5%, impaired nutrient utilization, and modestly advanced molting. It also induced a time-dependent juvenile hormone (JH)-associated response: JH III decreased at 24 h, reached its lowest level at 48 h, and partially recovered by 72 h, and was again lower than the control at 96–120 h. These changes were accompanied by altered JH-related gene expression and biochemical indices. Molecular docking indicated structural compatibility between PISCF and the O. furnacalis AstC receptor. These findings suggest that PISCF is a bioactive AstC-derived core motif and a potential scaffold for peptide-based insect growth regulator discovery.