Instituto de Investigaciones Bioquímicas de La Plata (CONICET-UNLP), Facultad de Ciencias Médicas, La Plata, Argentina.
Centro Regional de Estudios Genómicos (UNLP), Facultad de Ciencias Exactas, La Plata, Argentina.
Insect Mol Biol. 2020 Oct;29(5):431-443. doi: 10.1111/imb.12653. Epub 2020 Aug 7.
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.
昆虫表皮的碳氢化合物主要参与表皮的防水功能，但也参与化学通讯，并调节杀虫剂和微生物的渗透。昆虫碳氢化合物生物合成的最后一步是由昆虫特异性细胞色素 P450 的 4G 亚家族（CYP4G）完成的。在三锥虫属的 Rhodnius prolixus 和 Triatoma infestans 中已经报道了两个基因（CYP4G106 和 CYP4G107）。在这项工作中，对 R. prolixus 中的这两个基因进行了分子和功能表征，并评估了它们对昆虫生存的相关性。这两个基因几乎只在表皮中表达，并且表达模式依赖于发育阶段和摄食状态。CYP4G106 的沉默显著减少了直链碳氢化合物的产生，而 CYP4G107 的沉默则观察到甲基支链碳氢化合物的显著减少。使用不同的醛作为碳氢化合物前体的分子对接分析预测直链醛与 CYP4G106 的结合更好，而甲基支链醛与 CYP4G107 的结合更好。将沉默的昆虫暴露于干燥应激的生存生物测定表明，CYP4G107 决定了 R. prolixus 表皮的防水性能。这是首次报道两种 CYP4G 对主要形成直链或甲基支链碳氢化合物的体内特异性，以及它们对昆虫干燥的不同贡献。
