Insights into chemosensory genes of Pagiophloeus tsushimanus adults using transcriptome and qRT-PCR analysis

Pagiophloeus tsushimanus is a new, destructive, and monophagous weevil pest that thrives on Cinnamomum camphora, found in Shanghai. The functions of chemosensory genes involved in the host location and intraspecific communication of P. tsushimanus remain unknown. The male-female transcriptomes of P. tsushimanus adults were assembled using Illumina sequencing, and we focused on all chemosensory genes in transcriptomes. In general, 58,088 unigenes with a mean length of 1018.19 bp were obtained. In total, 39 odorant binding proteins (OBPs), 10 chemosensory proteins (CSPs), 22 olfactory receptors (ORs), 16 gustatory receptors (GRs), eight ionotropic receptors (IRs), and five sensory neuron membrane proteins (SNMPs) were identified. PtsuOBPs comprised four subfamilies (20 Minus-C, one Plus-C, two Dimer, and 15 Classic). Both PtsuOBPs and PtsuCSPs contained a highly conserved sequence motif of cysteine residues. PtsuORs including one olfactory receptor co-receptors (Ptsu/Orco) comprised seven predicted transmembrane domains. Phylogenetic analysis revealed that PtsuOBPs, PtsuCSPs, and PtsuORs in P. tsushimanus exhibited low homology compared to other insect species. The results of tissue- and sex-specific expression patterns indicated that PtsuOBPs and PtsuORs were highly abundant in the antennae; whereas, PtsuCSPs were not only highly abundant in antennae, but also abdominal apexes, wings, and legs. In conclusion, these results enrich the gene database of P. tsushimanus, which may serve as a basis for identifying novel targets to disrupt olfactory key genes and may provide a reverse validation method to identify attractants for formulating potential eco-friendly control strategies for this pest.