Genome-Wide Identification and Expression Analyses of Odorant-Binding Proteins in Hoverfly Eupeodes corollae

Chemosensory systems are fundamental for insects to regulate behaviors such as prey detection, oviposition, and pollination. Despite their importance, the molecular mechanisms underlying chemosensation remain poorly understood in many insect groups. Hoverflies (Syrphidae), whose larvae are efficient aphid predators and adults act as pollinators, represent a functionally important but understudied lineage. Building on the genome of Eupeodes corollae that we recently published, we selected this dominant and widespread species as a representative model and performed a genome-wide identification and analysis of odorant-binding proteins (OBPs) to provide a molecular foundation for understanding chemosensory recognition mechanisms. Accordingly, a total of 47 OBPs were identified and classified into Classic, Minus-C, and Plus-C subfamilies, with conserved motifs and structural features observed within each group. Next, phylogenetic analysis revealed that several EcorOBPs are homologous to functionally characterized OBPs in other Diptera, suggesting conserved evolutionary roles. Moreover, chromosomal mapping showed that Minus-C EcorOBPs cluster on chromosome 2, and Ka/Ks analysis indicated strong purifying selection, reflecting evolutionary stability. In addition, synteny analysis demonstrated that E. corollae shares more collinear OBP gene pairs with predatory hoverflies (Episyrphus balteatus and Scaeva pyrastri) than with the saprophagous species Eristalis tenax, consistent with ecological divergence. Finally, transcriptomic profiling revealed tissue-specific expression patterns, including antennal-biased EcorOBP1 linked to olfaction and reproductive tissue-biased EcorOBP11 linked to reproduction, highlighting candidate genes for functional studies. Together, these findings provide a comprehensive characterization of OBPs in E. corollae and offer molecular insights into chemosensory mechanisms that support both pest control and pollination services.