Functional Characterization of Prothoracicotropic Hormone in Larval Development and Diapause of Ostrinia furnacalis

Prothoracicotropic hormone (PTTH) is a secretory neuropeptide initiating insect metamorphosis via ecdysteroid synthesis. While the PTTH–ecdysone axis is well-established in development, its specific role in diapause regulation and the underlying mechanisms in agricultural pests like Ostrinia furnacalis are less understood. To address this, we identified O. furnacalis’ PTTH gene (OfPTTH) and investigated its spatiotemporal expression and function using RNAi and 20-hydroxyecdysone (20E) rescue assays. Our findings show that OfPTTH expression was lowest during diapause, significantly increasing upon its termination, and exhibiting an extended developmental periodicity during diapause. OfPTTH-silencing was associated with reduced expression of ecdysone-signaling genes, leading to broad physiological disruptions including altered ecdysone and juvenile hormone signaling, inhibited insulin/IGF signaling, suppressed lipid metabolic reprogramming (triglyceride accumulation), and decreased heat shock protein expression. These events ultimately caused larval diapause-like developmental arrest, pupation failure, and mortality. Exogenous 20E treatment promoted pupation in OfPTTH-knockdown larvae and restored the expression of several downstream ecdysone-signaling genes, suggesting that impaired 20E signaling contributes to the observed developmental abnormalities. This study supports an important role of the PTTH–20E axis in O. furnacalis development and diapause-associated regulation and provides a basis for further evaluation of OfPTTH as a potential target for RNAi-based pest management.