A microbially derived tyrosine-sulfated peptide mimics a plant peptide hormone

New Phytol. 2017 Jul;215(2):725-736. doi: 10.1111/nph.14609. Epub 2017 May 30.


The biotrophic pathogen Xanthomonas oryzae pv. oryzae (Xoo) produces a sulfated peptide named RaxX, which shares similarity to peptides in the PSY (plant peptide containing sulfated tyrosine) family. We hypothesize that RaxX mimics the growth-stimulating activity of PSY peptides. Root length was measured in Arabidopsis and rice treated with synthetic RaxX peptides. We also used comparative genomic analyses and reactive oxygen species burst assays to evaluate the activity of RaxX and PSY peptides. Here we found that a synthetic sulfated RaxX derivative comprising 13 residues (RaxX13-sY), highly conserved between RaxX and PSY, induces root growth in Arabidopsis and rice in a manner similar to that triggered by PSY. We identified residues that are required for activation of immunity mediated by the rice XA21 receptor but that are not essential for root growth induced by PSY. Finally, we showed that a Xanthomonas strain lacking raxX is impaired in virulence. These findings suggest that RaxX serves as a molecular mimic of PSY peptides to facilitate Xoo infection and that XA21 has evolved the ability to recognize and respond specifically to the microbial form of the peptide.

Keywords: PSY1; RaxX; XA21; Xanthomonas oryzae pv. oryzae; molecular mimicry; root growth; tyrosine-sulfated peptide.

MeSH terms

  • Arabidopsis / drug effects
  • Arabidopsis / growth & development
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / pharmacology*
  • Host-Pathogen Interactions
  • Molecular Mimicry
  • Oryza / drug effects
  • Oryza / growth & development
  • Oryza / microbiology
  • Peptides / chemistry
  • Peptides / pharmacology*
  • Plant Diseases / microbiology
  • Plant Growth Regulators / chemistry
  • Plant Growth Regulators / pharmacology
  • Plant Proteins / chemistry*
  • Plant Proteins / pharmacology
  • Plant Roots / drug effects
  • Plant Roots / growth & development
  • Plants, Genetically Modified
  • Signal Transduction
  • Tyrosine / chemistry
  • Xanthomonas / genetics
  • Xanthomonas / pathogenicity*


  • Arabidopsis Proteins
  • Bacterial Proteins
  • Peptides
  • Plant Growth Regulators
  • Plant Proteins
  • Tyrosine