Identification and Expression Profile of Chemosensory Genes in the Small Hive Beetle Aethina tumida

SIMPLE SUMMARY: The small hive beetle is a destructive pest of honeybees, causing severe economic damage to the apiculture industry. Chemosensory genes play key roles in insect behavior, such as foraging and mating partners. However, the chemosensory genes are lacking in the small hive beetle. In order to better understand its chemosensory process at the molecular level, a total of 130 chemosensory genes, including 38 odorant receptors, 24 ionotropic receptors, 14 gustatory receptors, 3 sensory neuron membrane proteins, 29 odorant binding proteins, and 22 chemosensory proteins were identified from the transcriptomic data of antennae and forelegs. Reverse-transcription PCR showed that 3 OBPs (AtumOBP3, 26 and 28) and 3 CSPs (AtumCSP7, 8 and 21) were highly expressed in antennae. Overall, this study could provide a basis for elucidating functions of these chemosensory genes at the molecular level. ABSTRACT: Aethina tumida is a parasite and predator of honeybee causing severe loss to the bee industry. No effective and environmentally friendly methods are available to control this pest at present. Chemosensory genes play key roles in insect behavior which can potentially be used as targets for developing environmentally friendly pest control agents. In this study, the putative chemosensory genes in antennae and forelegs of A. tumida involved in olfaction or contact chemical communication of adults were investigated using RNA transcriptome sequencing and PCR methods. Based on transcriptomic data, unigenes encoding 38 odorant receptors (ORs), 24 ionotropic receptors (IRs), 14 gustatory receptors (GRs), 3 sensory neuron membrane proteins (SNMPs), 29 odorant binding proteins (OBPs), and 22 chemosensory proteins (CSPs) were identified. The analyses of tissue expression profiles revealed that genes encoding 38 ORs, 13 antennal IRs, 11 GRs, 1 SNMP, 24 OBPs, and 12 CSPs were predominately expressed in antennae. No significant differences in expression levels of these genes were found between males and females. Genes encoding 5 non-NMDA iGluRs, 3 GRs, 2 SNMPs, 5 OBPs, and 12 CSPs were predominately expressed in forelegs. RT-PCR assays for SNMPs, OBPs and CSPs further revealed that 3 OBPs (AtumOBP3, 26 and 28) and 3 CSPs (AtumCSP7, 8 and 21) were highly expressed in antennae. Our results enrich the gene inventory of A. tumida and facilitate the discovery of potential novel targets for developing new pest control measures.