<i>Proteobacteria</i> Contain Diverse flg22 Epitopes That Elicit Varying Immune Responses in <i>Arabidopsis thaliana</i>

Bacterial flagellin protein is a potent microbe-associated molecular pattern. Immune responses are triggered by 22-amino-acid epitope derived from flagellin, known as flg22, upon detection the pattern recognition receptor FLAGELLIN-SENSING2 (FLS2) in multiple plant species. However, increasing evidence suggests that flg22 epitopes of several bacterial species not universally immunogenic to plants. We investigated whether immunogenicity systematically differs between classes phylum Proteobacteria, using dataset 2,470 sequences. To predict which encode highly epitopes, we queried custom motif ( 11 [ST]xx[DN][DN]xAGxxI 21 ) sequences, followed sequence conservation analysis and structural modeling. These data led us hypothesize most γ- β-Proteobacteria immunogenic, whereas α-, δ-, ε-Proteobacteria weakly moderately immunogenic. test this hypothesis, generated synthetic peptides representative each proteobacterial class, monitored their ability elicit an immune response Arabidopsis thaliana. The strong oxidative bursts, ε-, α-Proteobacteria moderate, weak, or no response, respectively. suggest conserved across Proteobacteria. postulate divergence taxonomic class was present prior evolution FLS2, ligand specificity A. thaliana FLS2 driven β-Proteobacteria, monophyletic group containing many common phytopathogens. [Formula: see text] Copyright © 2021 Author(s). This open access article distributed under CC BY 4.0 International license .