Identification and Expression Profiling of Olfactory-Related Genes in Exolontha castanea (Coleoptera: Melolonthinae) Using Tissue-Specific Transcriptomics

Exolontha castanea is an important subterranean pest of sugarcane in China, currently controlled mainly by chemical insecticides. However, prolonged and improperly timed insecticide application has exacerbated infestations, necessitating the development of eco-friendly management strategies. Given the pivotal role of olfactory-related genes in host-seeking, mating, and oviposition, deciphering the olfactory mechanisms of E. castanea may support environmentally sound pest management. In this study, we sequenced transcriptomes from different tissues of male and female E. castanea and annotated olfactory-related genes. We identified 35 odorant binding proteins (OBPs), 12 chemosensory proteins (CSPs), 51 odorant receptors (ORs), 21 ionotropic receptors (IRs), and 4 sensory neuron membrane proteins (SNMPs). Expression profiling indicated that 13 OBPs, 6 CSPs, 16 ORs, 5 IRs, and 2 SNMPs were moderately or highly expressed in the antennae, and among these, 4 OBPs, 4 CSPs, 1 IR and 1 SNMP were also moderately or highly expressed in non-olfactory tissues. In addition, 8 OBPs, 1 CSP, 5 IRs and 1 SNMP displayed moderate or high expression levels only in non-olfactory tissues, including the head, leg, thorax, and abdomen. Based on these findings, the potential functions of these olfactory-related genes are discussed. This study represents the first comprehensive catalog of olfactory-related genes in E. castanea, laying a solid foundation for future functional characterization and novel sustainable pest management strategy development.