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

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 H 2 O 2 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.