Molecular characterization of orco and its role in foraging behavior in the Formosan subterranean termite, Coptotermes formosanus

Subterranean termites are eusocial insects that live underground and are rarely exposed to the open environment. To build their nests and forage for food, workers construct extensive networks of tunnels in an organized and cooperative way. The blind workers and soldiers communicate through non-visual signals, which include vibro-acoustic signals, and more importantly, chemical cues. Several pheromones that mediate fundamental behaviors, such as trail-following, alarm, and nestmate recognition, have been identified in different species. However, the molecular basis of chemosensation is poorly understood in subterranean termites. In this study, we identified the full-length mRNA transcript of the odorant receptor co-receptor (orco) and investigated its spatial and temporal expression profiles in the Formosan subterranean termite, Coptotermes formosanus. The orco gene is highly conserved in insects and required for the function of olfaction. It encodes a chaperone protein, which interacts with different odorant receptors to form a cation channel for the translation of chemical cues into nerve impulses. Our results showed that orco was predominantly expressed in the antennae of all castes, including worker, soldier, female and male alate, and it was expressed in all developmental stages, which further include egg, larvae, pre-soldier, and nymph. In addition, we found that the expression level of orco is reduced with the increasing period of starvation in workers, which suggests a link between olfactory sensitivity and food deprivation. Our results provided the molecular characteristics of orco in a subterranean termite, and further studies are warranted to understand the role of orco in feeding and tunneling behavior