Meeting Abstract
Cnidarians perceive their environment and respond through the innate immune system by recognizing ligands and molecular patterns that send signals to trigger immune physiological responses. Transcriptional evidence underlying immune priming by recurrent bacterial challenges within the anemone, Exaiptasia pallida, identified an ionotropic glutamate receptor (iGluR) as a highly up-regulated protein among immune challenged anemones. iGluRs are transmembrane ion channels involved in chemo-sensing and in plants implicated in sensing pathogen- and damage-associated molecular patterns (PAMPs, DAMPs) that act together for hosts to differentiate pathogenic-damaging microbes from beneficial or harmless microbes. E. pallida iGluR ligand-binding domain indicates these iGluRs are not specific to classical synaptic-involved NMDA, kainate, or AMPA ligands. Those findings support the hypothesis that E. pallida iGluRs belong to a cnidarian-specific expansion within the phylogeny of iGluRs, and retained molecular characteristics to respond to chemical stimuli. Based on this, we postulate that iGluRs may mediate PAMP-triggered immunity via calcium channels by pattern-recognition particles. We tested this hypothesis by measuring iGluR expression response profiles to sub-lethal bacterial challenges. Challenging E. pallida anemones with the bacterium V. coralliilyticus had a more significant affect on expression patterns than S. marcescens. Some iGluRs displayed cyclic gene expression profiles, which has prompted further exploration into diel rhythmicity of expression of cnidarian chemosensory genes. Previous studies have shown a good number of genes in cnidarians seem to be regulated under circadian rhythm. These findings provide further functional analysis to understand the role of cnidarian iGluRs.
