Analysis and identification of chemosensory genes in the transcriptome of adult Rhoptroceros cyatheae

Rhoptroceros cyatheae (Hymenoptera) belongs to Rhopographus of Selandriidae. It mainly causes large-scale infestations during the sprouting period of Alsophila spinulosa ,and is one of the key herbivorous insects damaging this endangered fern. R. cyatheae possesses chemosensory genes in its body that detect, bind, and transduce chemical signals associated with host location, feeding, mating, and oviposition. However, to date, no reports have been published on the chemosensory genes of R. cyatheae . Thus, based on the transcriptome database of male and female adults of R. cyatheae , a total of 30,296 unigenes wereidentified, with an N50 length of 3,286 bp. By comparing with six major public databases, namely NR, Swiss-Prot, Pfam, eggNOG, GO, and KEGG, a total of 11,109 unigenes were annotated, accounting for 36.67% of the total unigenes. Among these annotated unigenes, the NR database was the largest, reaching 10,774, whereas the number of unigenes annotated in the KEGG database was the smallest, at 6,300. Based on the annotation information, we identified 90 candidate chemosensory genes of R. cyatheae , including 11 OBPs, 10 CSPs, 6 NPC2s, 24 ORs (comprising 23 typical OR genes and 1 Orco gene), 20 IRs, 15 GRs and 4 SNMPs. A phylogenetic tree of chemosensory genes was subsequently constructed to investigate the sequence identitybetween the chemosensory genes of R. cyatheae and those of other insect species. Furthermore, 13 chemosensory genes were differentially expressed between males and females, and their tissue expression profiles were verified via RT‒qPCR. These findings lay a solid molecular foundation for future investigations on the gene functions and olfactory perception mechanisms of R. cyatheae .