Odorant-binding protein 84a-1 mediates detection of Guire No.82 mango volatiles in Bactrocera dorsalis: from structural analysis to behavioral validation

<i>Bactrocera dorsalis</i> is a serious pest of mango, causing heavy losses during fruit ripening. Odorant-binding proteins (OBPs) are pivotal in insect olfaction, facilitating the detection of host plant volatiles. In this study, we focused on <i>OBPs</i> that mediate responses to volatiles from the Guire No.82 mango. Quantitative real-time PCR showed cultivar-dependent expression of six antennal OBP genes. Among these, <i>BdorOBP84a-1</i> was highly expressed in adults fed on Guire No.82. The 3D structure of BdorOBP84a-1 was predicted with AlphaFold3, showing six α-helices and three disulfide bonds forming a hydrophobic pocket. Molecular docking and 100-ns MD simulations indicated strong and stable binding of sesquiterpenes. Caryophyllene and ledene showed the lowest binding free energies (-31.87 and -30.62 kcal/mol) and stable RMSD/RMSF values. Key residues, including PHE95, ILE109 and PHE133, contributed to binding through hydrophobic and aromatic interactions. Y-tube behavioral assays validated these computational predictions. Caryophyllene attracted males at very low (0.01%) and high (10%) doses, females responded selectively at 0.1% and 1%, ledene attracted males at 0.1% and 10%, These findings suggest that BdorOBP84a-1 mediates recognition of mango sesquiterpenes and that caryophyllene and ledene are promising leads for new attractants in <i>B. dorsalis</i> management.