Tissue, developmental, and caste-specific expression of odorant binding proteins in a eusocial insect, the red imported fire ant, Solenopsis invicta

Abstract

Insects interact with the surrounding environment via chemoreception, and in social insects such as ants, chemoreception functions to mediate diverse behaviors including food acquisition, self/non-self recognition, and intraspecific communication. The invasive red imported fire ant, Solenopsis invicta, has spread worldwide, displaying a remarkable environmental adaptability. Odorant binding proteins (OBPs) are chemical compound carriers, involved in diverse physiological processes including odor detection and chemical transport. S. invicta contains a highly divergent 17-member OBP gene family, that includes an ant-specific expansion and the social organization implicated Gp-9 (OBP3) gene. A systematic gene expression analysis of the SiOBP repertoire was performed across social caste (workers, male and female alates), tissues (antennae, head, thorax, and abdomen), and developmental stages (egg, larvae, and pupae), revealing that although SiOBPs were expressed in the antennae, the major regions of expression were in the head and thorax across all castes, and the abdomen in male and female alates. SiOBPs were very highly expressed in female alates and at somewhat lower levels in male alates and workers. SiOBPs were differentially expressed, with unique signatures in various castes and tissues, suggesting functionality of SiOBPs beyond olfaction Expression patterns of SiOBP subgroups also showed relationships with their evolutionary relatedness.

Fire ant social chromosomes: Differences in number, sequence and expression of odorant binding proteins

“…). For previously known OBPs, the topology of our phylogenetic tree agrees with previously published trees (Gotzek et al ; Zhang et al ), with the exception of the position of SiOBP15 (low bootstrap values in all trees) and SiOBP5 .…”

Antennal Proteome of the Solenopsis invicta (Hymenoptera: Formicidae): Caste Differences in Olfactory Receptors and Chemosensory Support Proteins

“…There is evidence supporting the similarity of worker and male OBP expression down to low levels. A study of fire ant antennal OBP mRNA ( Zhang et al 2016 ) shows a similar pattern to our proteomics data in Table 1 for high-level transcripts, but no gap between workers and males appears in the low-level OBP transcripts, which are at about the same levels.…”

Has gene expression neofunctionalization in the fire ant antennae contributed to queen discrimination behavior?

“…Genes may also neofunctionalize in terms of gene expression. Prior studies have shown that many OBPs, including Gp‐9 and SiOBP12 , are expressed in nonantennal tissues (Morandin et al, ; Pracana et al, ; Zhang, Wanchoo, Ortiz‐Urquiza, Xia, & Keyhani, ). We tested whether SiOBP12 (in an assay that cannot distinguish between paralogs) was also differentially expressed in the worker heads (without antennae), thoraces, and abdomens using qRT‐PCR assays.…”