Abstract: Odorant binding proteins (OBPs) are widely involved in olfactory perception and play a key role in transporting hydrophobic odorants across the sensillum lymph to the olfactory receptors (ORs). Understanding the roles of insect OBPs in chemical communication would help us elucidate the mechanism of insect olfaction perception and lay the theoretical basis for controlling the target pests by interfering with insect chemoreception. In this study, a novel OBP gene AlucOBP7 (GenBank accession no.: JQ675724) was identified from the green plant bug, Apolygus lucorum (Meyer-Dür), and then the recombinant AlucOBP7 was prokaryotically expressed in Escherichia coli and purified. Fluorescence competitive binding assays were conducted to explore the binding properties of AlucOBP7 with 10 cotton volatiles and 6 sex pheromone analogs using a fluorescence probe, N-phenyl-1-naphthylamine (1-NPN). The results revealed that for the 10 cotton volatiles, AlucOBP7 showed certain binding abilities with 2-hexanone and methylis salicylas, with the dissociation constants of 55.13 μmol/L and 28.26 μmol/L, respectively. For the 6 sex pheromone analogs, the AlucOBP7 had a strong binding affinity with 4-oxo-(E)-2-hexenal, with the dissociation constant of 23.14 μmol/L. Ethyl butyrate, butyl butanoate and hexyl hexanoate showed moderate binding abilities with AlucOBP7, and their dissociation constants were 30.58, 39.26 and 35.81 μmol/L, respectively. We so inferred that AlucOBP7 may be a pheromone binding protein of the green plant bug and play dual roles in the perception of sex pheromone and plant volatiles.

Key words: Apolygus lucorum, odorant binding proteins, sex pheromone, prokaryotic expression, fluorescence competitive binding, dissociation constant