Chemosensory System Decoding: Transcriptome‐Wide Identification and Expression Profiling of Olfactory Genes in <i>Lytta sifanica</i>

The insect olfactory system relies on a sophisticated repertoire of olfactory-related proteins to enable precise odor detection and subsequent signal transduction. Their expression and regulation are crucial for mediating communication between themselves and environments. <i>Lytta sifanica</i> (Coleoptera: Meloidae), a species of significant economic importance, represents a notable subject for olfactory studies, particularly as it is renowned for producing the medically relevant toxin cantharidin. However, the molecular basis of olfactory sensation in the Blister Beetle <i>Lytta sifanica</i> has not yet been characterized. In this study, the transcriptomes of adult <i>L. sifanica</i> antennae were sequenced and analyzed. A total of 70 chemosensory genes, including 17 odorant binding proteins (OBPs), 5 chemosensory proteins (CSPs), 13 gustatory receptors (GRs), 17 odorant receptors (ORs), 13 ionotropic receptors (IRs) and 5 sensory neuron membrane proteins (SNMPs) were identified based on sequence homology analysis and phylogenetic reconstruction. The expression profiles of all candidate genes were confirmed by RT-PCR across multiple tissues, including antennae, head, mouthparts, pronotum, foreleg tarsus, abdomen skin, and wings. The results revealed that olfactory-related protein families were broadly expressed in the tested tissues, though with distinct tissue-specific patterns among different gene families. Among the identified chemosensory genes, eleven members are predominantly expressed in the antennae (<i>Lsif_OBP1/2/19d, Lsif_OR2/20/49b, Lsif_IR2a, Lsif_GR7/127, Lsif_CSP1</i>, and <i>Lsif_SNMP2/4</i>). In contrast, twenty-two members were exclusively expressed in the mouthparts (<i>Lsif_OBP70/56d2, Lsif_GR12a/21/28a/68a</i>), foreleg tarsus (<i>Lsif_OR6/67c, Lsif_GR12,</i> and <i>Lsif_OBP2</i>) and were abundant in the non-olfactory tissues head (<i>Lsif_OBP99a, Lsif_OR9a/49b, Lsif_IR25a/56e,</i> and <i>Lsif_CSP6</i>), pronotum (<i>Lsif_OBP5/C20, Lsif_ORco, Lsif_OR13</i>, and <i>Lsif_IR7</i>), abdomen skin (<i>Lsif_SNMP5</i>), suggesting their various functions in the olfactory system of <i>L. sifanica</i>. This research offers an extensive resource for investigating the chemoreception mechanism in beetle <i>L. sifanica</i>.