Transcriptional Control of Quality Differences in the Lipid-Based Cuticle Barrier inDrosophila suzukiiandDrosophila melanogaster

Cuticle barrier efficiency in insects depends largely on cuticular lipids. To learn about the evolution of cuticle barrier function, we compared the basic properties of the cuticle inward and outward barrier function in adults of the fruit fliesDrosophila suzukiiandDrosophila melanogasterthat live on fruits sharing a similar habitat. At low air humidity,D. suzukiiflies desiccate faster thanD. melanogasterflies. We observed a general trend indicating that in this respect males are less robust than females in both species. Xenobiotics penetration occurs at lower temperatures inD. suzukiithan inD. melanogaster. Likewise,D. suzukiiflies are more susceptible to contact insecticides thanD. melanogasterflies. Thus, both the inward and outward barriers ofD. suzukiiare less efficient. Consistently,D. suzukiiflies have less cuticular hydrocarbons (CHC) that participate as key components of the cuticle barrier. Especially, the relative amounts of branched and desaturated CHCs, known to enhance desiccation resistance, show reduced levels inD. suzukii. Moreover, the expression ofsnustorr(snu) that encodes an ABC transporter involved in barrier construction and CHC externalization, is strongly suppressed inD. suzukii. Hence, species-specific genetic programs regulate the quality of the lipid-based cuticle barrier in these two Drosophilae. Together, we conclude that the weaker inward and outward barriers ofD. suzukiimay be partly explained by differences in CHC composition and by a reduced Snu-dependent transport rate of CHCs to the surface. In turn, this suggests thatsnuis an ecologically adjustable and therefore relevant gene in cuticle barrier efficiency.