Objective Odorant Binding Proteins (OBP) are the first key proteins involved in the insect olfactory sensory pathway, responsible for binding and transporting odorant molecules to olfactory receptors. Dendrolimus houi Lajonquiere is an important foliage-feeding pest in southern China, and investigated of its OBP gene family is essential for understanding larval foraging behavior as well as adult recognition and oviposition site selection, thereby providing a molecular basis for pest control strategies.

Methods In this study, using the OBPs of the model species, Bombyx mori, were identified from D.houi and its closely related species D. punctatus. Phylogenetic relationships were reconstructed, and the characteristics of OBPs of D.houi, including motifs, physicochemical properties, transmembrane spiral region, secondary and tertiary structures were analyzed. In addition, the expression levels of OBPs of D.houi at different developmental stages were explored.

Results A total of 41 OBPs were identified in D.houi and were evolutionarily grouped into six subfamilies: PBP/GOBP, ABPⅠ, ABPⅡ, Plus-C, Minus-C, and CRLBP. Sequence structures of members of different subfamilies of OBPs were distinctly differentiated, and members of the same subfamily had similar biochemical and structural properties. The nature and structure of a few members were different from members of same subfamilies. The OBP gene family was classified into six categories of genes based on differences in their expression across six developmental stages of D.houi. The class Ⅰ, Ⅱ, and Ⅲ genes were specifically expressed during the larval stage(instars 1～3, 4～5, and 6～7), class Ⅳ genes were specifically expressed during the pupal stage, class Ⅴ genes were highly expressed in the adult stage, and class Ⅵ genes were highly expressed in both the egg and adult stages.

Conclusion The OBPs of D.houi can be divided into six subfamilies, with diverse structural features and expression patterns, suggesting functional diversification. In addition to olfactory-related functions, certain OBPS may also be involved in regulating growth, development and reproduction. The study provides a molecular basis for resolving the mechanism of OBP-associated olfaction in D.houi.