Functional characterization and immunolocalization of odorant binding protein 1 in the lucerne plant bug, Adelphocoris lineolatus (GOEZE)

In the insect phylum, the relationships between individuals and their environment are often modulated by chemical communication. Odorant binding proteins (OBPs) are widely and robustly expressed in insect olfactory organs and play a key role in chemosensing and transporting hydrophobic odorants across the sensillum lymph to the olfactory receptor neuron. In this study, a novel OBP gene (AlinOBP1) in the lucerne plant bug, Adelphocoris lineolatus was identified, cloned and expressed. Real-time PCR results indicated that the expression level of AlinOBP1 gene differed in each developmental stage (from first instar to adult) and was predominantly expressed in the antennae of adults. The expression level of AlinOBP1 was 1.91 times higher in male antennae than in female antennae. The binding properties of AlinOBP1 with 114 odorants were measured using a fluorescence probe, N-phenyl-1-naphthylamine (1-NPN), with fluorescence competitive binding. The results revealed that AlinOBP1 exhibits high binding abilities with two major putative pheromone components, ethyl butyrate and trans-2-hexenyl butyrate. In addition, it was observed that six volatiles released from cotton, octanal, nonanal, decanal, 2-ethyl-1-hexanol, β-caryophyllene and β-ionone also bind to AlinOBP1. Immunocytochemistry analysis showed that AlinOBP1 was expressed in the sensillum lymph of sensilla trichodica and sensilla basiconca. Our results demonstrate that AlinOBP1 may function as a carrier in the chemoperception of the lucerne plant bug.