title: The Arabidopsis flagellin receptor FLS2 mediates the perception of Xanthomonas Ax21 secreted peptides.
abstract: Detection of microbes by plants relies in part on an array of pattern-recognition receptors that recognize conserved microbial signatures, so-called "microbe-associated molecular patterns." The Arabidopsis thaliana receptor-like kinase FLS2 is the pattern-recognition receptor for bacterial flagellin. Similarly to FLS2, the rice transmembrane protein XA21 is the receptor for the sulfated form of the Xanthomonas oryzae pv. oryzae secreted protein Ax21. Here we show that Ax21-derived peptides activate Arabidopsis immunity, triggering responses similar to those elicited by flagellin, including an oxidative burst, induction of defense-response genes, and enhanced resistance to bacterial pathogens. To identify Arabidopsis Xa21 functional homologs, we used a reverse genetics approach to screen T-DNA insertion mutants corresponding to all 47 of the Arabidopsis genes encoding non-RD kinases belonging to the interleukin-1 receptor-associated kinase (IRAK) family. Surprisingly, among all of these mutant lines, only fls2 mutants exhibited a significant loss of response to Ax21-derived peptides. Ax21 peptides also failed to activate defense-related responses in an fls2-24 mutant that does not bind Flg22. Moreover, a Flg22Δ2 variant of Flg22 that binds to FLS2 but does not activate FLS2-mediated signaling suppressed Ax21-derived peptide signaling, indicating mutually exclusive perception of Flg22 or Ax21 peptides by FLS2. The data indicate that FLS2 functions beyond flagellin perception to detect other microbe-associated molecular patterns.
authors.affiliation: Department of Genetics, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Cristian H
authors.initials: CH
authors.lastname: Danna
authors.forename: Yves A
authors.initials: YA
authors.lastname: Millet
authors.forename: Teresa
authors.initials: T
authors.lastname: Koller
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Han
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Bent
authors.forename: Pamela C
authors.initials: PC
authors.lastname: Ronald
authors.forename: Frederick M
authors.initials: FM
authors.lastname: Ausubel
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005408:Flagellin / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000737:chemistry; D007107:Immune System; D007113:Immunity, Innate; D010455:Peptides / Q000737:chemistry; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D013997:Time Factors; D014974:Xanthomonas / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D010455:Peptides; D010940:Plant Proteins; D005408:Flagellin; D006861:Hydrogen Peroxide; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis