The MAP kinase substrate MKS1 is a regulator of plant defense responses

Erik Andreasson, Thomas Jenkins, Peter Brodersen, Stephan Thorgrimsen, Nikolaj HT Petersen, Shijiang Zhu, Jin‐Long Qiu, Pernille Micheelsen, Anne Rocher, Morten Petersen, Mari‐Anne Newman, Henrik Bjørn Nielsen, Heribert Hirt, Imre Somssich, Ole Mattsson, John Mundy

Author Affiliations

  1. Erik Andreasson1,,
  2. Thomas Jenkins1,,
  3. Peter Brodersen1,
  4. Stephan Thorgrimsen1,
  5. Nikolaj HT Petersen1,
  6. Shijiang Zhu1,
  7. Jin‐Long Qiu1,
  8. Pernille Micheelsen1,
  9. Anne Rocher1,
  10. Morten Petersen1,
  11. Mari‐Anne Newman2,
  12. Henrik Bjørn Nielsen3,
  13. Heribert Hirt4,
  14. Imre Somssich5,
  15. Ole Mattsson1 and
  16. John Mundy*,1
  1. 1 Molecular Biology Institute, University of Copenhagen, Copenhagen, Denmark
  2. 2 Plant Biology Institute, Royal Veterinary and Agricultural University, Frederiksberg, Denmark
  3. 3 BioCentrum‐DTU, Technical University of Denmark, Lyngby, Denmark
  4. 4 Biocenter, University of Vienna, Vienna, Austria
  5. 5 Max‐Planck‐Institute, Köln, Germany
  1. *Corresponding author. Molecular Biology Institute, University of Copenhagen, Oster Farimagsgade 2A, 1353 Copenhagen K, Denmark. Tel.: +45 3532 2131; Fax: +45 3532 2128; E‐mail: mundy{at} or mundy{at}
  1. These authors contributed equally to this work

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Arabidopsis MAP kinase 4 (MPK4) functions as a regulator of pathogen defense responses, because it is required for both repression of salicylic acid (SA)‐dependent resistance and for activation of jasmonate (JA)‐dependent defense gene expression. To understand MPK4 signaling mechanisms, we used yeast two‐hybrid screening to identify the MPK4 substrate MKS1. Analyses of transgenic plants and genome‐wide transcript profiling indicated that MKS1 is required for full SA‐dependent resistance in mpk4 mutants, and that overexpression of MKS1 in wild‐type plants is sufficient to activate SA‐dependent resistance, but does not interfere with induction of a defense gene by JA. Further yeast two‐hybrid screening revealed that MKS1 interacts with the WRKY transcription factors WRKY25 and WRKY33. WRKY25 and WRKY33 were shown to be in vitro substrates of MPK4, and a wrky33 knockout mutant was found to exhibit increased expression of the SA‐related defense gene PR1. MKS1 may therefore contribute to MPK4‐regulated defense activation by coupling the kinase to specific WRKY transcription factors.

  • Received March 9, 2005.
  • Accepted June 10, 2005.
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