Abstract: Abstract: Insects depend critically on their sophisticated and sensitive chemoreception system to recognize and distinguish a variety of semiochemical signals from the environment. Olfaction is a sensory modality responsible for the olfactory signal transduction, which can evoke insect survival and reproduction behaviors, such as foraging, oviposition, capulation, and avoiding predators. As essential proteins in the normally functioning olfactory system, odorant binding proteins (OBPs) initially interact with external lipophilic chemicals in the process of olfactory sensing, and transfer them to chemical receptor neurons to activate olfactory receptors (ORs) distributed on the surface of dendritic membrane. In recent years, with the rapid development of high-throughput sequencing and molecular biology technologies, more and more OBPs have been identified in different species and their biological functions have been explored. Insect OBPs are a class of soluble small molecular proteins, and generally contain a stable and compact hydrophobic binding pocket consisting of 6 αhelices, where the conformational change varies with insect species and ligand structures. The expression of OBPs is not limited to olfactory organs, but also in non-olfactory tissues such as mouthparts, legs, midgut and glands. Insect OBPs can perform different physiological roles in olfaction recognition, gustatory perception, nutrient transport, pheromone synthesis and release, and histological development and differentiation. It is reasonable to suspect that the common property linking their very different functions is the ability of OBPs to bind and solubilize small hydrophobic compounds including pheromone components, common odor molecules, and nonvolatile substances. The stability and versatility of OBPs suggest their extensive application potentials in many fields including pest control, biosensors, analytical chemistry and ecology. In this article we reviewed the relevant studies of insect OBPs over the last 20 years to provide theoretical references for the in-depth study on the functions of OBPs.

Key words:  Insect, olfaction, odorant binding protein, olfactory system, olfactory receptor, ligand structure