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Scientia Silvae Sinicae ›› 2021, Vol. 57 ›› Issue (9): 130-139.doi: 10.11707/j.1001-7488.20210913

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Localization, Ligand Binding Characteristics and Ligand Activity of an Odorant Binding Protein, AplaOBP2, from Agrilus planipennis

Xuan Song1,2,3,Zehua Wang1,Guoyue Yu1,Fan Wang1,4,Shuang Shan2,Yongjun Zhang2,Shanning Wang1,*   

  1. 1. Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Sciences Beijing 100097
    2. State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing 100193
    3. College of Plant Protection, China Agricultural University Beijing 100193
    4. Agricultural Science Research Institute, the Third Division of Xinjiang Production and Construction Corps Tumshuq 843900
  • Received:2019-11-26 Online:2021-09-25 Published:2021-11-29
  • Contact: Shanning Wang

Abstract:

Objective: Agrilus planipennis is a borer of ash tree (Emerald ash borer). In this paper we studied the expression of the odorant binding protein AplaOBP2 in the antenna of Agrilus planipennis, and investigate the ligand binding characteristics and ligand activity of the AplaOBP2. The purpose of this study is to use AplaOBP2 as target to discover new semiochemicals for A. planipennis. Method: The recombinant AplaOBP2 of A. planipennis was expressed in the prokaryotic expression system. The localization of expression of AplaOBP2 in the antenna of A. planipennis was studied using immunocytochemistry assay. The binding characteristics of the recombinant AplaOBP2 protein with 58 candidate ligands were analyzed by fluorescence competitive binding assay.The electrophysiological and behavioral responses of A. planipennis to AplaOBP2 ligands were studied by electroantennography(EAG) and a Y-tube olfactometer. Result: The recombinant AplaOBP2 protein was successfully expressed in the prokaryotic expression system.The result of immunofluorescence localization showed that AplaOBP2 protein was expressed in the lymph of olfactory sensilla S. basiconica I.The results of fluorescence competitive binding assay showed that in vitro, the recombinant AplaOBP2 exhibited high binding affinities with 6 kinds of ligands, including trans-2-hexenal, trans-2-heptenal, benzaldehyde, 4'-ethylacetophenone, 3', 4'-dimethoxyacetophenone, β-ionone, and their dissociation constants KD were 4.44, 4.17, 5.20, 2.91, 3.45 and 0.63 μmol·L-1, respectively. All AplaOBP2 ligands could trigger antennal responses of both males and females at the dosage of 10 mg·mL-1. The behavioral test showed that 10 mg·mL-1 trans-2-hexenal had significant attraction to female adults, and 10 mg·mL-1 β-ionone had a significant evading effect on the female adults. Conclusion: AplaOBP2 is expressed in olfactory sensilla and can selectively bind affinities with aldehydes and ketones, suggesting that AplaOBP2 might play a role in olfactory perception. This study supports the role of OBPs as targets to discover new semiochemicals that could act as either attractants or repellents for A. planipennis.

Key words: Agrilus planipennis, odorant binding proteins, sensilla basiconica, fluorescence binding assay, EAG response, behavioral response

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