Transcriptome Analysis and Identification of Chemosensory Genes in Baryscapus dioryctriae (Hymenoptera: Eulophidae)

SIMPLE SUMMARY: The parasitic wasp Baryscapus dioryctriae (Hymenoptera: Eulophidae) was originally discovered in the pupae of Dioryctria insects. It can also parasitize many Pyralidae pests, such as Ostrinia furnacalis, Chilo suppressalis and Galleria mellonella, suggesting that this parasitic wasp has a great potential to serve as a natural enemy against agricultural and forest insect pests. The olfactory system plays an important role in this wasps’ reception of chemical signals emitted from their surrounding environment, and various chemosensory genes are involved in this system. In this study, seven chemosensory gene families, namely, the odorant-binding proteins (OBPs), chemosensory proteins (CSPs), Niemann–Pick type C2 proteins (NPC2s), odorant receptors (ORs), ionotropic receptors (IRs), gustatory receptors (GRs) and sensory neuron membrane proteins (SNMPs) of B. dioryctriae were identified and analyzed using transcriptome sequencing and bioinformatic analyses. Moreover, the quantitative expression of the candidate chemosensory genes, which are female antennae- and ovipositor-biased expression was validated by RT-qPCR. These results lay a molecular foundation for further investigation of the mechanism of chemoreception by the olfactory system during host recognition, location, and oviposition site selection in B. dioryctriae. ABSTRACT: Baryscapus dioryctriae is a pupal endoparasitoid of many Pyralidae pests and has been used as a biocontrol agent against insect pests that heavily damage the cone and seed of the Korean pine. The olfactory system of wasps plays an essential role in sensing the chemical signals during their foraging, mating, host location, etc., and the chemosensory genes are involved in detecting and transducing these signals. Many chemosensory genes have been identified from the antennae of Hymenoptera; however, there are few reports on the chemosensory genes of Eulophidae wasps. In this study, the transcriptome databases based on ten different tissues of B. dioryctriae were first constructed, and 274 putative chemosensory genes, consisting of 27 OBPs, 9 CSPs, 3 NPC2s, 155 ORs, 49 GRs, 23 IRs and 8 SNMPs genes, were identified based on the transcriptomes and manual annotation. Phylogenetic trees of the chemosensory genes were constructed to investigate the orthologs between B. dioryctriae and other insect species. Additionally, twenty-eight chemosensory genes showed female antennae- and ovipositor-biased expression, which was validated by RT-qPCR. These findings not only built a molecular basis for further research on the processes of chemosensory perception in B. dioryctriae, but also enriched the identification of chemosensory genes from various tissues of Eulophidae wasps.