A Xanthomonas uridine 5'-monophosphate transferase inhibits plant immune kinases

Nature. 2012 Apr 15;485(7396):114-8. doi: 10.1038/nature10962.


Plant innate immunity is activated on the detection of pathogen-associated molecular patterns (PAMPs) at the cell surface, or of pathogen effector proteins inside the plant cell. Together, PAMP-triggered immunity and effector-triggered immunity constitute powerful defences against various phytopathogens. Pathogenic bacteria inject a variety of effector proteins into the host cell to assist infection or propagation. A number of effector proteins have been shown to inhibit plant immunity, but the biochemical basis remains unknown for the vast majority of these effectors. Here we show that the Xanthomonas campestris pathovar campestris type III effector AvrAC enhances virulence and inhibits plant immunity by specifically targeting Arabidopsis BIK1 and RIPK, two receptor-like cytoplasmic kinases known to mediate immune signalling. AvrAC is a uridylyl transferase that adds uridine 5'-monophosphate to and conceals conserved phosphorylation sites in the activation loop of BIK1 and RIPK, reducing their kinase activity and consequently inhibiting downstream signalling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology*
  • Arabidopsis / immunology*
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / antagonists & inhibitors*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / immunology
  • Arabidopsis Proteins / metabolism
  • Bacterial Proteins / metabolism*
  • Brassica / immunology
  • Brassica / microbiology
  • Molecular Sequence Data
  • Phosphorylation
  • Plant Diseases / immunology
  • Plant Diseases / microbiology
  • Plant Immunity* / immunology
  • Plants, Genetically Modified
  • Protein Kinases / chemistry
  • Protein Kinases / immunology
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / immunology
  • Protein-Serine-Threonine Kinases / metabolism
  • Signal Transduction
  • Virulence
  • Xanthomonas campestris / enzymology*
  • Xanthomonas campestris / immunology
  • Xanthomonas campestris / pathogenicity


  • Arabidopsis Proteins
  • Bacterial Proteins
  • Protein Kinases
  • RPM1-induced protein kinase, Arabidopsis
  • BIK1 protein, Arabidopsis
  • Protein-Serine-Threonine Kinases