Molecular Characterization and Functional Analysis of Odorant-Binding Proteins in Ectropis grisescens

Insect odorant-binding proteins (OBPs) are promising molecular targets for developing novel pest management strategies by modulating chemoreception-driven behaviors. The tea gray geometrid <i>Ectropis grisescens</i> (Lepidoptera, Geometridae) is a major pest in tea plantations, causing substantial economic losses in China. In this study, we identified 18 OBPs from <i>E. grisescens</i> antennal transcriptome. All of the encoded proteins possessed N-terminal signal peptides and conserved cysteine residues, behaviors which are characteristic of insect OBPs. Phylogenetic analysis categorized these proteins into plus-C, minus-C, and classic OBP subfamilies. MEME motif analysis identified conserved sequence features potentially involved in odor detection. Tissue- and sex-specific expression profiling showed that <i>EgriGOBP1-2</i>, <i>OBP3</i>, <i>OBP8</i>, and <i>OBP13</i> were highly expressed in the antennae of both sexes, suggesting roles in olfactory communication. Among them, <i>EgriGOBP1-2</i>, <i>OBP3</i>, and <i>OBP13</i> exhibited similar expression levels between males and females, while other <i>EgriOBPs</i> were predominantly expressed in the legs, wings, or other tissues, indicating additional physiological functions beyond chemoreception. To investigate functional specificity, we selected antenna-enriched EgriGOBP2 for ligand-binding analysis. Fluorescence binding assays demonstrated that EgriGOBP2 exhibited broad binding affinity toward 8 of 12 host volatiles and 11 of 12 plant essential oil-derived volatiles. These combined findings lay the foundation for mechanistic studies of chemical recognition in <i>E. grisescens</i> and provide insights into the development of ecologically friendly pest control alternatives.