Characterization of CYP4G Integument Genes in the Chagas Disease Vector, Rhodnius prolixus.

A. B. DULBECCO; D. E. MORICONI; CALDERÓN FERNÁNDEZ, G. M.

Congreso; II Congress of the Latin American Society for Vector Ecology ?Control of endemic zoonotic and vector-borne emerging and re-emerging diseases: Current challenges in Latin America?; 2022

The heteropteran subfamily Triatominae is a group of hematophagous insects mostly found in Latin America. They are vectors of Chagas disease, a parasitic illness affecting 6 to 7 million people worldwide. Insect cuticle hydrocarbons are involved primarily in waterproofing the cuticle, but also participate in chemical communication and regulate the penetration of insecticides and microorganisms. The last step in insect hydrocarbon biosynthesis is carried out by an insect-specific cytochrome P450 of the 4G subfamily (CYP4G). Two genes (CYP4G106 and CYP4G107) have been reported in the triatomines Rhodnius prolixus and Triatoma infestans. In this study, the molecular and functional characterization of both R. prolixus CYP4G genes has been carried out in order to elucidate their roles in HC biosynthesis. Measurement of gene expression by RT-qPCR shows that both genes are expressed almost exclusively in the integument and have an expression pattern dependent on the developmental stage and feeding status. Knockdown of both CYP4G genes by RNA interference (RNAi) significantly diminished HC amounts both in the cuticle and internal tissues, with a selective cutback of straight or methyl-branched chains depending on the gene silenced. Molecular docking analysis between both CYP4G enzymes and different aldehyde precursors predicted their preferred interaction with straight or methyl-branched chains. Thus, both CYP4G genes are involved in HC synthesis, albeit with different substrate specificity. Survival bioassays exposing the silenced insects to desiccation stress showed that CYP4G107 is determinant for the waterproofing properties of the R. prolixus cuticle. Our work demonstrates that distinct CYP4Gs have different specificity to form straight or methyl-branched HCs, and also provides clues to explain such specificity on the basis of the enzyme-substrate interactions obtained by a docking analysis. Further studies are needed to discover additional functions of these genes, especially in those insects that express three or more of them. Also, as our results indicate that there is compensatory mechanism regulating the expression of these genes, additional research is needed to elucidate this issue.