In the chemosensory system of insects, odorant-binding proteins (OBPs) and odorant-degrading enzymes (ODEs) play a role in the host location process. This study identified and analyzed chemosensory-related genes from the transcriptomes of different tissues of male and female adults of Tomicus yunnanensis. Subsequently, host odorants from Pinus yunnanensis and non-host odorants from Alnus ferdinandi-coburgii were used to treat the adults of T. yunnanensis to clarify the gene expression changes in the insects and, combined with molecular docking, to explore the mechanism of the non-host odor interfering with the host localisation of T. yunnanensis. A total of 137 chemosensory-related genes were obtained, among which TyunOBP6 was specifically highly expressed in the antennae of T. yunnanensis; TyunCYP4G2 and TyunCYP6DF1 were highly expressed in the remnants of T. yunnanensis, selected as key genes for further research. The odor interference experiment results show that both host and non-host odorants caused up-regulation of TyunOBP6 in antennal expression, and significant changes in the expression of TyunCYP4G2 and TyunCYP6DF1 in the remnants were also observed. The molecular docking results indicate that non-host compounds could compete with host compounds for protein binding sites. The non-host odor of A. ferdinandi-coburgii can interfere with TyunOBPs and TyunCYPs in T. yunnanensis and affect their host localization.

This study characterized the transcriptome of Cacia cretifera thibetana and explored odorant binding proteins (OBPs) and their interaction with host-specific compounds. A total of 36 samples from six different organs including antennae, head, thorax, abdomen, wings, and legs (12 groups with 3 replicates per group) from both male and female insects were collected for RNA extraction. Transcriptomic analysis revealed a total of 89,897 transcripts as unigenes, with an average length of 1036 bp. Between male and female groups, 31,095 transcripts were identified as differentially expressed genes (DEGs). The KEGG pathway analysis revealed 26 DEGs associated with cutin, suberine, and wax biosynthesis and 70, 48, and 62 were linked to glycerophospholipid metabolism, choline metabolism in cancer, and chemokine signaling pathways, respectively. A total of 31 OBP genes were identified. Among them, the relative expression of 11 OBP genes (OBP6, 10, 12, 14, 17, 20, 22, 26, 28, 30, and 31) was confirmed by quantitative RT-PCR in different tissues. Seven OBP genes including CcreOBP6 and CcreOBP10 revealed antennae-specific expression. Further, we selected two OBPs (CcreOBP6 and CcreOBP10) for functional analysis to evaluate their binding affinity with 20 host odorant compounds. The CcreOBP6 and CcreOBP10 exhibited strong binding affinities with terpineol and trans-2-hexenal revealing their potential as an attractant or repellent for controlling C. cretifera thibetana.