The grapevine flagellin receptor Vv FLS 2 differentially recognizes flagellin‐derived epitopes from the endophytic growth‐promoting bacterium Burkholderia phytofirmans and plant pathogenic bacteria

Abstract

Summary: The role of flagellin perception in the context of plant beneficial bacteria still remains unclear. Here, we characterized the flagellin sensing system flg22–FLAGELLIN SENSING 2 (FLS 2) in grapevine, and analyzed the flagellin perception in the interaction with the endophytic plant growth‐promoting rhizobacterium (PGPR) B urkholderia phytofirmans. The functionality of the grapevine FLS 2 receptor, Vv FLS 2, was demonstrated by complementation assays in the A rabidopsis thaliana fls2 mutant, which restored flg22‐induced H2O2 production and growth inhibition. Using synthetic flg22 peptides from different bacterial origins, we compared recognition specificities between V v FLS 2 and At FLS 2. In grapevine, flg22‐triggered immune responses are conserved and led to partial resistance against B otrytis cinerea. Unlike flg22 peptides derived from P seudomonas aeruginosa or X anthomonas campestris, flg22 peptide derived from B. phytofirmans triggered only a small oxidative burst, weak and transient defense gene induction and no growth inhibition in grapevine. Although, in A rabidopsis, all the flg22 epitopes exhibited similar biological activities, the expression of V v FLS 2 into the fls2 background conferred differential flg22 responses characteristic for grapevine. These results demonstrate that V v FLS 2 differentially recognizes flg22 from different bacteria, and suggest that flagellin from the beneficial PGPR B. phytofirmans has evolved to evade this grapevine immune recognition system.