The role of CYP4Gs involved in hydrocarbon formation in the survival, reproduction, and pyrethroid resistance of Triatoma infestans, a major Chagas disease vector

Very long-chain normal and branched hydrocarbons are essential for insect physiology and ecology. The final metabolic step of hydrocarbon formation involves an oxidative decarbonylation carried out by cytochrome P450 from family 4, subfamily G (CYP4G). Triatoma infestans Klug (Hemiptera: Reduviidae: Triatominae) has two CYP4G genes, named CYP4G106 and CYP4G107. In this study, we have silenced in T. infestans the expression of both genes by RNA interference in order to assess the relevance of hydrocarbons to survival, reproductive physiology, and insecticide susceptibility. Gene knockdown led to a significant decrease (≈ 79%) in total cuticle hydrocarbons, especially normal alkanes. A reduced number of CYP4G-silenced nymphs completed metamorphosis, and adult survival-particularly among females-was markedly diminished. Although mating behavior was not affected by silencing, the reproductive fitness was severely impaired as CYP4G-silenced females laid about 77% fewer eggs per female than control females. Egg hatching was almost completely abolished by CYP4G-silencing. Furthermore, CYP4G gene knockdown increased susceptibility to the insecticide deltamethrin, leading to a 40%-50% higher mortality compared to control insects. These findings highlight the essential role of CYP4G genes in cuticle function, survival, and reproductive fitness and suggest that disruption of hydrocarbon biosynthesis can enhance insecticide efficacy, making it a potential target for control of these insects.