Odorant Receptor OR45a Mediates Female-Specific Attraction to cis-Linalool Oxide in Bactrocera dorsalis

<i>Bactrocera dorsalis</i> Hendel is a devastating invasive pest that costs billions of dollars in agricultural losses worldwide. Current control strategies rely heavily on male-specific attractants such as methyl eugenol, which are less effective against females, underscoring the need for female-targeted control approaches. Here, we investigated the molecular mechanisms underlying female attraction to cis-linalool oxide by functionally characterizing the odorant receptor <i>OR45a</i>, identifying it as a molecular target for female-oriented pest management. We conducted spatiotemporal expression analysis of <i>OR45a</i> in response to cis-linalool oxide, followed by RNAi and behavioral assays. Phylogenetic analysis of OR45a orthologs from 10 Dipteran species, combined with structural topology prediction and solvent-accessible surface area (ASA) analysis, helped identify functional domains and residues. Site-directed mutagenesis and two-electrode voltage clamp (TEVC) recordings validated receptor-ligand interactions. Results showed that <i>OR45a</i> was specifically upregulated in antennae, with peak expression at 10 days post-eclosion, coinciding with oviposition periods. RNAi significantly reduced <i>OR45a</i> transcript levels and female behavioral responses to cis-linalool oxide. Phylogenetic analysis showed that OR45a is highly conserved within Tephritidae but diverges from Drosophilidae, with closest similarity to <i>Anastrepha ludens</i>, indicating ecological specialization. Structural modeling predicted a canonical seven-transmembrane architecture with three extracellular loops forming the ligand-binding pocket. Among five key residues identified, Leu122 and Ile146 were essential for ligand recognition, while Tyr107 contributed to protein stability. These findings reveal a female-specific odorant receptor mechanism in <i>B. dorsalis</i> and provide molecular targets for <i>OR45a</i>-based attractants, addressing a critical gap in female-focused pest management.