Abstract: 【Aim】 The aim of this study is to explore the localization of the odorant binding protein AplaOBP3 in antennae of Agrilus planipennis and its ligand binding characteristics, and to compare the function of AplaOBP3 with the reported AplaOBP1 and AplaOBP2. 【Methods】 The recombinant AplaOBP3 of A. planipennis was expressed in prokaryotic expression system. The polyclonal antibody against AplaOBP3 was prepared and detected by Western blot assay. Immunocytochemical technique was used to localize the expression of AplaOBP3 in antennal sensilla of A. planipennis. Its binding characteristics to 58 compounds were determined by fluorescence competitive binding assay, and compared with those of AplaOBP1 and AplaOBP2 previously reported. 【Results】 The recombinant protein AplaOBP3 was successfully expressed in prokaryotic expression system. The immunolocalization results showed that AplaOBP3 was expressed in the antennal sensilla basiconica type I. The results of fluorescence competitive binding assay showed that AplaOBP3 had strong binding capabilities with trans-2-hexenal, benzaldehyde, 4′-ethylacetophenone, β-ionone and ocimene, with the dissociation constant KD values of 6.20, 4.03, 5.24, 1.72 and 4.83 μmol/L, respectively. AplaOBP3 and AplaOBP2 had similar expression and ligand binding properties. 【Conclusion】 AplaOBP3 and AplaOBP2 have similar expression and ligand binding properties, and both may be involved in olfactory perception together and play a role in host localization in A. planipennis.

Key words: Agrilus planipennis, odorant binding protein, antennal sensilla; immunocytochemistry, ligand binding characteristics, olfactory perception