CYP4G acts beyond the cuticular barrier as a multifunctional regulator coordinating insect development and reproduction

Abstract BACKGROUND The insect cytochrome P450 subfamily CYP4G has long been recognized as the terminal oxidative decarbonylase catalyzing cuticular hydrocarbon biosynthesis, and it plays an important role in insecticide tolerance. Whether members of this subfamily also participate in the metabolism of other cuticular constituents or contribute to broader life processes such as postembryonic development and reproduction remains poorly understood. RESULTS We used Tribolium castaneum as a model and applied RNA interference‐mediated gene silencing to build a loss‐of‐function model to systematically dissect the biological roles of TcCYP4G7 . TcCYP4G7 was markedly enriched in the integument and fat body across all developmental stages. Silencing of TcCYP4G7 perturbed cuticular chitin metabolism, thinned the cuticle and disorganized its pore canal architecture, thereby lowering body water content under desiccation stress. In parallel, TcCYP4G7 governed molting and metamorphosis through the 20‐hydroxyecdysone (20E) pathway and modulated reproduction in adult females through the juvenile hormone (JH) pathway. Notably, exogenous 20E injection failed to rescue the pupation defects caused by TcCYP4G7 depletion. Supplementation with JH substantially ameliorated ovarian atrophy and restored egg laying, yet the resulting eggs remained entirely unable to hatch. CONCLUSION TcCYP4G7 acts as a multifunctional hub that not only coordinates cuticular metabolism and water balance but also participates in development and reproduction, offering new insights into the functional versatility of insect cuticular metabolic enzymes. © 2026 Society of Chemical Industry.