Genome-Wide Analysis of Odorant-Binding Proteins and Chemosensory Proteins in the Bean bug Riptortus pedestris

Abstract

Insects have sensitive olfactory systems to interact with environment and respond to the change in host plant conditions. Key genes in the system can be potential targets for developing new and efficient pest behaviour control methods. Riptortus pedestris is an important soybean pest in East Asia and has caused serious damage to the soybean plants in Huang-Huai-Hai region of China. However, the current treatment of pests is dominated by chemical insecticides and lacks efficient sustainable prevention and control technologies. In this study, we identified 49 putative odorant-binding proteins (OBPs) (43 were new genes) and 25 chemosensory proteins (CSPs) (17 were new genes) in R. pedestris genome. These OBP and CSP genes are clustered in highly conserved groups from other hemipteran species in phylogenetic trees. Most RpedOBPs displayed antennal-biased expression. Among the 49 RpedOBPs, 33 were significantly highly expressed in the antennae, including three male-biased and nine female-biased. While many RpedCSPs were detected both in the antennae and in non-antennal tissues, only 11 RpedCSPs displayed antennal-biased expression, in which four RpedCSPs were male-biased and five RpedCSPs were female-biased. Some OBP and CSP genes showed sex-biased expression profiles. Our results not only provide a foundation for future exploration of the functions of RpedOBPs and RpedCSPs but also aid in developing environmentally friendly insecticides in the future.

Keywords: Riptortus pedestris; chemosensory proteins; genome analysis; odorant-binding proteins; olfactory.

FIGURE 1

The number of OBP and CSP genes in different insect species, obtained from genome (*) or antennal transcriptome (#). The digits by the histogram bars represent number of OBP and CSP genes in different hemipteran species (Aphis gossypii, Nilaparvata lugens, Sogatella furcifera, Adelphocoris lineolatus, Adelphocoris suturalis, Nysius ericae, R. pedestris) and phylogenetic tree was built by these hemipteran species COI genes.

FIGURE 2

Localization of OBPs and CSPs in the R. pedestris genome. Based on the annotation file of R. pedestris, we acquired the localization of OBP and CSP genes in genome. (A) The RpedOBPs in the R. pedestris genome, they clustered together in 4 chromosomes and one scaffold. (B) The RpedCSPs in the R. pedestris genome, they clustered together in 4 chromosomes.

FIGURE 3

Genomic structure of R. pedestris OBPs and CSPs. Based on the annotation file of R. pedestris, we acquired genomic structures of OBP and CSP genes. (A) Numbers of exon/intron and exon/intron structures of RpedOBPs. (B) Numbers of exon/intron and exon/intron structures of RpedCSPs.

FIGURE 4

Phylogenetic tree of OBPs. Phylogenetic neighbor-joining tree was constructed using MEGA7 based on alignment results of MEGA7. A phylogenetic neighbor-joining tree was constructed using the OBPs protein that removed signal peptide. Bootstrap values higher than 70 were displayed.

FIGURE 5

Phylogenetic tree of CSPs. Phylogenetic neighbor-joining tree was constructed using MEGA7 based on alignment results of MEGA7. A phylogenetic neighbor-joining tree was constructed using the CSPs protein that removed signal peptide. Bootstrap values higher than 50 were displayed.

FIGURE 6

Tissue expression profiles of R. pedestris OBPs by qRT-PCR. The relative expression level is presented as mean ± SE (n = 3). The heatmap use Log2 and row scale based the relative expression level data. Different capital letters mean a significant difference between tissues (p < 0.05, ANOVA, LSD). He, heads; Th, thoraxes; Ab, abdomens; Le, legs; Wi, wings; FA, female antennae; MA, male antennae.

FIGURE 7

Tissue expression profiles of R. pedestris CSPs by qRT-PCR. The relative expression level is presented as mean ± SE (n = 3). The heatmap use Log2 and row scale based the relative expression level data. Different capital letters mean a significant difference between tissues (p < 0.05, ANOVA, LSD). He, heads; Th, thoraxes; Ab, abdomens; Le, legs; Wi, wings; FA, female antennae; MA, male antennae.