Deciphering the role of Rhodnius prolixus CYP4G genes in straight and methyl‐branched hydrocarbon formation and in desiccation tolerance

• Published in: Insect molecular biology 2020-10, Vol.29 (5), p.431-443
• Main Authors: Dulbecco, A. B., Moriconi, D. E., Lynn, S., McCarthy, A., Juárez, M. P., Girotti, J. R., Calderón‐Fernández, G. M.
• Format: Article
• Language: English
• Subjects: Aldehydes; Animals; Bioassays; Biosynthesis; Chain branching; Chains; Chemical communication; cuticle waterproofing; Cuticles; CYP4G; Cytochrome; Cytochrome P450; Cytochrome P450 Family 4 - genetics; Cytochrome P450 Family 4 - metabolism; Cytochromes P450; Desiccation; Genes; Hydrocarbons; Hydrocarbons - metabolism; Insect Proteins - genetics; Insect Proteins - metabolism; Insecticides; Insects; Integument; methyl‐branched hydrocarbons; Microorganisms; Molecular docking; Nymph - genetics; Nymph - growth & development; Nymph - physiology; Rhodnius - genetics; Rhodnius - growth & development; Rhodnius - physiology; Rhodnius prolixus; straight‐chain hydrocarbons; Survival; Waterproofing
• ISSN: 0962-1075; 1365-2583
• DOI: 10.1111/imb.12653

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 work, their molecular and functional characterization is carried out in R. prolixus, and their relevance to insect survival is assessed. Both genes are expressed almost exclusively in the integument and have an expression pattern dependent on the developmental stage and feeding status. CYP4G106 silencing diminished significantly the straight‐chain hydrocarbon production while a significant reduction – mostly of methyl‐branched chain hydrocarbons – was observed after CYP4G107 silencing. Molecular docking analyses using different aldehydes as hydrocarbon precursors predicted a better fit of straight‐chain aldehydes with CYP4G106 and methyl‐branched aldehydes with CYP4G107. Survival bioassays exposing the silenced insects to desiccation stress showed that CYP4G107 is determinant for the waterproofing properties of the R. prolixus cuticle. This is the first report on the in vivo specificity of two CYP4Gs to make mostly straight or methyl‐branched hydrocarbons, and also on their differential contribution to insect desiccation. CYP4G106 and CYP4G107 are highly expressed in the integument tissue of Rhodnius prolixus. CYP4G107 knockdown mostly reduces the methyl‐branched hydrocarbon content while CYP4G106 knockdown reduces the straight‐chain hydrocarbon amounts. Docking analysis predicts a preferred interaction between straight‐chain aldehydes with CYP4G106 and branched‐chain aldehydes with CYP4G107. CYP4G107‐silenced insects show a reduced survival rate under desiccation stress compared to control insects.