A high-quality chromosome-level genome assembly of the oligophagous fruit fly Bactrocera tsuneonis (Diptera: Tephritidae) and insights into its host specificity

Abstract Background Bactrocera tsuneonis is a major pest of citrus, causing significant economic losses in fruit production. It exhibits a highly specialized host preference, primarily infesting citrus fruits. However, the genetic basis underlying its olfactory adaptation and host specificity remains largely unexplored. To elucidate the molecular mechanisms governing host selection in B. tsuneonis, we assembled a high-quality chromosome-level genome and performed comparative genomic, transcriptomic, and functional analyses of its chemosensory system. Results The genome of B. tsuneonis was assembled to a total size of 339 Mb, with a contig N50 of 11.21 Mb and a scaffold N50 of 59.93 Mb. Comparative genomic analysis revealed significant contractions in chemosensory-related gene families, particularly in odorant-binding proteins (OBPs) and odorant receptors (ORs), perhaps suggesting an adaptation to a narrow host range. Transcriptome analysis demonstrated that BtsuOBP83a and BtsuOBP83b were highly expressed in the antennae, and most ORs were predominantly expressed in the antennae. Functional assays confirmed that BtsuOBP83a selectively binds to 2 citrus volatiles, trans-nerolidol and piperitone, with strong affinity. Molecular docking and molecular dynamics simulations further revealed that BtsuOR7a-6 and BtsuOR7a-4 specifically interact with these volatiles, suggesting their role in host odor recognition. Conclusions Our high-quality genome of B. tsuneonis provides a valuable resource for genomic research and offers valuable insights into the genetic basis of its olfactory adaptation and host specificity. The findings highlight key molecular mechanisms underlying host selection and provide potential targets for behavior-based pest management strategies.