CYP4G100 contributes to desiccation resistance by mediating cuticular hydrocarbon synthesis in Bactrocera dorsalis

The oriental fruit fly Bactrocera dorsalis (Hendel) is expanding its distribution to higher latitudes. Our goal in this study was to understand how B. dorsalis adapts to higher latitude environments that are more arid than tropical regions. Cuticular hydrocarbons (CHCs) on the surface of the epicuticle in insects act as a hydrophobic barrier against water loss. The essential decarbonylation reaction in CHC synthesis is catalysed by CYP4G, a cytochrome P450 subfamily protein. Hence, in B. dorsalis it is necessary to clarify the function of the CYP4G gene and its role in desiccation resistance. CYP4G100 was identified in the B. dorsalis genome. The complete open reading frame (ORF) encodes a CYP4 family protein (552 amino acid residues) that has the CYP4G-specific insertion. This CYP4G gene was highly expressed in adults, especially in the oenocyte-rich peripheral fat body. The gene can be induced by desiccation treatment, suggesting its role in CHC synthesis and waterproofing. Silencing of CYP4G100 resulted in a decrease of CHC levels and the accumulation of triglycerides. It also increased water loss and resulted in higher desiccation susceptibility. CYP4G100 is involved in hydrocarbon synthesis and contributes to cuticle waterproofing to help B. dorsalis resist desiccation in arid environments.