OBP14 (Odorant-Binding Protein) Sensing in Adelphocoris lineolatus Based on Peptide Nucleic Acid and Graphene Oxide

SIMPLE SUMMARY: The alfalfa plant bug, Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae), is a serious agricultural pest in China. Previous studies have shown that olfaction plays a crucial role in the survival and reproduction of herbivorous insects, such as A. lineolatus, and OBPs (odorant-binding proteins) are involved in the initial steps of olfaction. Due to the complex intracellular environment in insects, detection of the expression of OBP genes by conventional methods is limited in vitro. In this study, we developed a PNA-GO- (peptide nucleic acid and graphene oxide) based mRNA biosensor that allows detection of the expression of the AlinOBP14 gene in A. lineolatus. We demonstrate that AlinOBP14 is expressed in the adult head, which is consistent with previous research on the expression profiles of AlinOBP14 in A. lineolatus using quantitative real-time PCR. The results demonstrate that the method we developed is both feasible and reliable. In addition, this method exhibited good stability and specificity in detection of chemically synthesized targets in vitro as well as the expression of the target OBP gene in vivo. ABSTRACT: OBPs play a crucial role in the recognition of ligands and are involved in the initial steps of semiochemical perception. The diverse expression of OBP genes allows them to participate in different physiological functions in insects. In contrast to classic OBPs with typical olfactory roles in A. lineolatus, the physiological functions of Plus-C OBPs remain largely unknown. In addition, detection of the expression of insect OBP genes by conventional methods is difficult in vitro. Here, we focused on AlinOBP14, a Plus-C OBP from A. lineolatus, and we developed a PNA-GO-based mRNA biosensor to detect the expression of AlinOBP14. The results demonstrated that AlinOBP14 plays dual roles in A. lineolatus. The AlinOBP14 is expressed beneath the epidermis of the vertex and gena in heads of A. lineolatus, and it functions as a carrier for three terpenoids, while AlinOBP14 is also expressed in the peripheral antennal lobe and functions as a carrier for endogenous compounds such as precursors for juvenile hormone (JH) and JHⅢ. Our investigation provides a new method to detect the expression of OBP genes in insects, and the technique will facilitate the use of these genes as potential targets for novel insect behavioral regulation strategies against the pest.