Comparative Transcriptome Analysis Revealed Differences in Odorant-Binding and Chemosensory Proteins Between Zoophytophagous and Phytozoophagous Mirid Bugs

Odorant-binding proteins (OBPs) and chemosensory proteins (CSPs) are essential for host-seeking behaviors in herbivorous and predatory insects. However, limited studies have examined differences in the OBP and CSP profiles between herbivores and predators. Mirid bugs, which ancestrally were predatory, provide an ideal model to investigate these differences because some of mirid species have evolved to develop herbivorous capacities. In this study, we compared compared OBP and CSP profiles among transcriptome analysis of one zoophytophagous and four phytozoophagous mirid bugs, identifying a total of 146 OBPs and 69 CSPs. The number of OBPs was similar between phytozoophagous (26 in Adelphocoris fasciaticollis, 29 in Adelphocoris lineolatus, 28 in Apolygus lucorum, and 32 in Adelphocoris suturalis) and zoophytophagous (31 in Nesidiocoris tenuis) species. However, the zoophytophagous specie had more CSPs than the phytozoophagous species. Phylogenetic analysis revealed two types of OBPs in mirid bugs, with classic OBPs being more abundant than plus-C OBPs. Transcriptome revealed that the number of OBPs with high expressions was higher in the phytozoophagous species (18) than in the zoophytophagous species (14). By contrast, more CSPs (10) exhibited high expressions in the zoophytophagous mirid bug compared with those in the phytozoophagous species (≤ 7). These results suggest that differences in the number and expression levels of OBPs and CSPs between zoophytophagous and phytozoophagous mirid bugs affect host-selection processes. In conclusion, the findings provide a basis for developing novel pest management strategies, including the use of natural enemies or behavioral regulation of mirid bugs through OBP and CSP gene manipulation.