Credible evidence shows that odorant binding proteins(OBPs)are required for insect olfaction perception and play a key role in transporting hydrophobic odorants across the sensillum lymph to the olfactory receptors(ORs).In the present study,a novel OBP(AlinOBP3)gene from the lucerne plant bug,Adelphocoris lineolatus,was cloned and expressed.The expression pattern of AlinOBP3 was evaluated by qPCR,which indicated that AlinOBP3 was dominantly expressed in antennae.The binding properties of AlinOBP3 with 9 cotton volatiles and 5 sex pheromone analogs were measured by fluorescence competitive binding assays with the fluorescence probe 1-NPN.The results revealed that of 9 cotton volatiles,Myrcene,β-Ocimene and α-Phellandrene can bind with AlinOBP3.α-Phellandrene especially bound to AlinOBP3 with a high binding affinity,with a dissociation constant of 56.68 μmol/L.Of the 5 sex pheromone analogs,Hexyl butyrate had the strongest binding affinity with AlinOBP3,with a dissociation constant as 59.53 μmol/L.Butyl butyrate,trans-2-Hexenyl butyrate and Ethyl butyrate had medium binding affinities with AlinOBP3,with dissociation constants of 227.39,108.77 and 143.47 μmol/L,respectively.The results suggest that AlinOBP3 might be a pheromone binding protein(PBP)with a dual-function for the perception of sex pheromones and plant volatiles. Credible evidence shows that odorant binding proteins (OBPs) are required for insect olfaction perception and play a key role in transporting hydrophobic odorants across the sensillum lymph to olfactory receptors (ORs) .In the present study, a novel OBP (AlinOBP3) gene from the lucerne plant bug, Adelphocoris lineolatus, was cloned and expressed. The expression pattern of AlinOBP3 was evaluated by qPCR, which indicated that AlinOBP3 was dominantly expressed in antennae. The binding properties of AlinOBP3 with 9 cotton volatiles and 5 sex pheromone analogs were measured by fluorescence binding binding assays with the fluorescence probe 1-NPN. The results revealed that of 9 cotton volatiles, Myrcene, β-Ocimene and α-Phellandrene can bind with AlinOBP3.α-Phellandrene especially bound to AlinOBP3 with a high binding affinity, with a dissociation constant of 56.68 μmol / L.Of the 5 sex pheromone analogs, Hexyl butyrate had the strongest binding affinity with AlinOBP3, with a dissociation constant a s 59.53 μmol / L. Butyl butyrate, trans-2-Hexenyl butyrate and Ethyl butyrate had medium binding affinities with AlinOBP3, with dissociation constants of 227.39, 108.77 and 143.47 μmol / L, respectively.The results suggest that AlinOBP3 might be a pheromone binding protein (PBP) with a dual-function for the perception of sex pheromones and plant volatiles.