Antennal transcriptome analysis of olfactory genes and tissue expression profiling of odorant binding proteins in Semanotus bifasciatus (cerambycidae: coleoptera)

Abstract

Background: Insect olfactory proteins can transmit chemical signals in the environment that serve as the basis for foraging, mate searching, predator avoidance and oviposition selection. Semanotus bifasciatus is an important destructive borer pest, but its olfactory mechanism is not clear. We identified the chemosensory genes of S. bifasciatus in China, then we conducted a phylogenetic analysis of the olfactory genes of S. bifasciatus and other species. And the expression profiles of odorant binding proteins (OBPs) genes in different tissues and different genders of S. bifasciatus were determined by quantitative real-time PCR for the first time.

Results: A total of 32 OBPs, 8 chemosensory proteins (CSPs), 71 odorant receptors (ORs), 34 gustatory receptors (GRs), 18 ionotropic receptors (IRs), and 3 sensory neuron membrane proteins (SNMPs) were identified. In the tissue expression analysis of OBP genes, 7 OBPs were higher expressed in antennae, among them, SbifOBP2, SbifOBP3, SbifOBP6, SbifOBP7 and SbifOBP20 were female-biased expression, while SbifOBP1 was male-biased expression and SbifOBP22 was no-biased expression in antennae. In addition, the expressed levels of SbifOBP4, SbifOBP12, SbifOBP15, SbifOBP27 and SbifOBP29 were very poor in the antennae, and SbifOBP4 and SbifOBP29 was abundant in the head or legs, and both of them were male-biased expression. While SbifOBP15 was highly expressed only at the end of the abdomen with its expression level in females three times than males. Other OBPs were expressed not only in antennae but also in various tissues.

Conclusion: We identified 166 olfactory genes from S. bifasciatus, and classified these genes into groups and predicted their functions by phylogenetic analysis. The majority of OBPs were antenna-biased expressed, which are involved in odor recognition, sex pheromone detection, and/or host plant volatile detection. However, also some OBPs were detected biased expression in the head, legs or end of the abdomen, indicating that they may function in the different physiological processes in S. bifasciatus.

Keywords: Antennal transcriptome; Odorant binding protein; Semanotus bifasciatus; Tissue expression profiles.

Fig. 1

Functional annotation of all Unigenes based on gene ontology (GO) categorization. GO analysis was performed for cellular components, molecular functions, and biological processes

Fig. 2

Heat-plot of FPKM values for SbifOBPs in female antennae (FAn) and male antennae (MAn). Relative expression levels are indicated by a 8-grade color scale. The genes were divided into group1-5 according to the expression level

Fig. 3

A maximum likelihood phylogenetic tree including candidate odor-binding proteins (OBPs) from Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifOBPs are shown in red. Minus-C OBP, GOBP/PBP and plus-C OBP lineages are found in the beige, gray and orange regions, respectively

Fig. 4

A maximum likelihood phylogenetic tree including CSP candidates for Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifCSPs are shown in red

Fig. 5

A maximum likelihood phylogenetic tree including candidate odorant receptors (OR) from Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifORs are shown in red. Specific OR and ORco lineages are found in the beige and gray regions, respectively

Fig. 6

A maximum likelihood phylogenetic tree including candidate gustatory receptors (GRs) for Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifGRs are shown in red. Sweet and bitter receptor lineages are found in the gray and beige regions, respectively

Fig. 7

A maximum likelihood phylogenetic tree including candidate ionotropic receptor (IRs) for Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifIRs are shown in red. The IR8A/25A, IR NMDA, and IR21A lineages are found in the gray, beige, and orange regions, respectively

Fig. 8

A maximum likelihood phylogenetic tree including candidate sensory neuron membrane proteins (SNMPs) of the orders Hymenoptera (blue), Diptera (green), Lepidoptera (purple), and Coleoptera (black). Target SbifSNMPs are shown in red. The SNMP1 and SNMP2 lineages are found in the gray and beige regions, respectively

Fig. 9

Expression patterns of candidate OBPs in S. bifasciatus. An: antennae; H: head; L: legs; AB: tail of the abdomen. The letters over the error bars (a-e) denote a significant difference (P < 0.05), and "N/a" indicates that the corresponding expression level was below the limit of detection. The genes were divided into group1-5 according to the expression level