Antennal and abdominal transcriptomes reveal chemosensory gene families in the coconut hispine beetle, Brontispa longissima

Antennal and abdominal transcriptomes of males and females of the coconut hispine beetle Brontispa longissima were sequenced to identify and compare the expression patterns of genes involved in odorant reception and detection. Representative proteins from the chemosensory gene families likely essential for insect olfaction were identified. These include 48 odorant receptors (ORs), 19 ionotropic receptors (IRs), 4 sensory neuron membrane proteins (SNMPs), 34 odorant binding proteins (OBPs) and 16 chemosensory proteins (CSPs). Phylogenetic analysis revealed the evolutionary relationship of these proteins with homologs from Coleopterans or other insects, and led to the identification of putative aggregation pheromone receptors in B. longissima. Comparative expression analysis performed by calculating FPKM values were also validated using quantitative real time-PCR (qPCR). The results revealed that all ORs and antennal IRs, two IR co-receptors (BlonIR8a and BlonIR25a) and one SNMP (BlonSNMP1a) were predominantly expressed in antennae when compared to abdomens, and approximately half of the OBPs (19) and CSPs (7) were enriched in antennae. These findings for the first time reveal the identification of key molecular components in B. longissima olfaction and provide a valuable resource for future functional analyses of olfaction, and identification of potential targets to control this quarantine pest.