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

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.

Keywords: Baryscapus dioryctriae; Eulophidae; chemosensory genes; transcriptome; wasp.

Figure 1

Phylogenetic tree of 233 odorant-binding proteins (OBPs) from B. dioryctriae and seven other Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in File S1. The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 2

Phylogenetic tree of 90 chemosensory proteins (CSPs) from B. dioryctriae and 11 other Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in File S2. The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 3

Phylogenetic tree of 29 Niemann–Pick type C2 proteins (NPC2s) from B. dioryctriae and other 10 Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in File S3. The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 4

Phylogenetic tree of 705 odorant receptors (ORs) from B. dioryctriae and three other Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in the Supplementary Materials (File S4). The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 5

Phylogenetic tree of 211 ionotropic receptors (IRs) from B. dioryctriae and 13 other Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in the Supplementary Materials (File S5). The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 6

Phylogenetic tree of 120 gustatory receptors (GRs) from B. dioryctriae and nine other insect species. The protein sequences used in this phylogenetic analysis are listed in the Supplementary Materials (File S6). The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 7

Phylogenetic tree of 29 sensory neuron membrane proteins (SNMPs) from B. dioryctriae and 12 other Hymenoptera species. The protein sequences used in this phylogenetic analysis are listed in the Supplementary Materials (File S7). The size and color of the dots reflect their bootstrap values. The color scale is shown on the left, with larger dots indicating larger bootstrap values.

Figure 8

GO enrichment of 393 up-regulated unigenes in FA. (a) Unigenes enriched into the molecular function category. (b) Unigenes enriched into the biological process category; GO enrichment of 365 up-regulated unigenes in MA. (c) Unigenes enriched into the molecular function category. (d) Unigenes enriched into the biological process category. (The size and color of the red and blue dots represent the count and p-value of the category, respectively, and their rulers are shown on the right side of each subgraph).

Figure 9

Expression profiles of antennae-biased chemosensory genes in B. dioryctriae. The chemosensory genes with female antennae-biased expression are marked in red, with a standard of q value < 0.005 &|log2 (fold change) > 2 when FA vs. MA. FA and MA: female and male antennae; FH and MH: female and male heads without antennae; Fab: female abdomens without ovipositors and digestive tracts; Fov: female ovipositors; Mge: male genitalia; Mab: male abdomens without genitalia and digestive tracts; T: male and female thoraxes; L: male and female legs.

Figure 10

Expression profiles of ovipositor-biased chemosensory genes in B. dioryctriae with Scheme 0. &|log2 (fold change) > 2 when Fov vs. other nine tissues. FA and MA: female and male antennae; FH and MH: female and male heads without antennae; Fab: female abdomens without ovipositors and digestive tracts; Fov: female ovipositors; Mge: male genitalia; Mab: male abdomens without genitalia and digestive tracts; T: male and female thoraxes; L: male and female legs.

Figure 11

Expression levels of 32 candidate chemosensory genes in different tissues. (FA and MA: female and male antennae; FH and MH: female and male heads without antennae; Fab: female abdomens without ovipositors and digestive tracts, Fov: female ovipositors; Mge: male genitalia; Mab: male abdomens without genitalia and digestive tracts; T: male and female thoraxes; L: male and female legs). Columns labeled with different letters are significantly different (p < 0.05).