A short grooved-peg specific odorant binding protein AlinOBP13 of Adelphocoris lineolatus displayed preferential binding behavior to terpenoids

Odorant binding proteins (OBPs) have been considered as one of important elements in insect olfactory perception and might be potential targets for the control of insect pests. In this study, an antenna-enriched odorant binding protein, AlinOBP13, was focused to investigate its contribution to the peripheral olfactory perception in the alfalfa plant bug, Adelphocoris lineolatus. The change of AlinOBP13 transcription in different developmental stages and effects by the starvation were addressed by qRT-PCR. The results showed that transcript was extremely high in adult stage and there was a clear correlation between AlinOBP13 transcription and feeding status. Base on the transmission electron microscopy and immunocytochemical labeling technique, the ultrastructures of different antennal sensilla in both female and male adults were illustrated. By labeling of AlinOBP13 antiserum, it was found that AlinOBP13 was restricted in the inner lumen and the cavities below the sensillum base of short grooved-pegs. Interestingly, multiporous sensilla trichodea, medium long sensilla basiconica and aporous sensilla chaetica were never labeled. This is the first report that insect OBP showed specific expression in short grooved-pegs of Hemipteran species. Fluorescence binding assays indicated that recombinant AlinOBP13 had a specific binding preference to terpenoids. Among all chemicals tested, terpenoids such as nerolidol, β-pinene, β-caryophyllene and trans-β-farnesene showed high binding affinities to AlinOBP13. In addition, the results of dose-dependent EAG recordings revealed that both female and male adult bugs indeed perceived most terpenoids, suggesting an apparent physiological relevance of AlinOBP13 in A. lineolatus chemoreception. This study showed that AlinOBP13 might act as a specific carrier of terpenoids and provided important information for further researches of olfaction mechanisms of A. lineolatus in response to environmental volatiles.

Keywords: Adelphocoris lineolatus, odorant binding proteins, expression profile, ligand-binding assays, immunocytochemical localization, terpenoid perception

Corresponding authors:

Yong-Jun Zhang, PhD. State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.  Email: yjzhang@ippcaas.cn;

Ze-Wen Liu, PhD. Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.  E-mail: jemunson@njau.edu.cn