Antennal transcriptome analysis of the chemosensory gene families in the Formosan subterranean termite, Coptotermes formosanus

Subterranean termites are eusocial insects that live in colonies with a well-defined system of castes that includes workers, soldiers, and reproductives. Workers perform different tasks such as foraging, brood care, and nest maintenance; while soldiers protect the colony from predators and competitive termite colonies. The reproductives (queen and king) are exclusively dedicated to produce offspring. Chemical communication is the most important way of communication in subterranean termites due to their lifestyle underground, and lack of functional eyes in workers and soldiers. Chemoreception in termites occurs primarily in the antennae, where several chemosensory gene families are expressed, including chemosensory proteins (CSPs), odorant binding proteins (OBPs), odorant receptors (ORs), and ionotropic receptors (IRs). Studies in ants, social bees and wasps have shown that the chemosensory genes are differentially expressed among castes and/or sexes, however, the molecular basis of chemosensation in termites is poorly understood.  In this study, we analyzed the antennal transcriptomes of workers, soldiers, female and male alates in the Formosan subterranean termite, Coptotermes formosanus. We identified more than 100 putative chemosensory genes belonging to the CSP, OBP, OR, or IR gene families in each caste/sex. In addition, our differential gene expression analysis revealed major differences between the reproductive (female and male alates) and non-reproductive (workers and soldiers) castes. Our results allowed the identification of caste-specific genes involved in chemosensation in the Formosan subterranean termite; however, further functional analysis will be required to unveil the specific function and biological relevance of each of these genes.