The Arabidopsis MAP kinase kinase MKK1 participates in defence responses to the bacterial elicitor flagellin

Authors

  • Tamás Mészáros,

    1. School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK,
    2. Department of Biochemistry of Food Technology, Budapest University of Technology and Economics, Műegyetem rkp. 3, 1111 Budapest, Hungary,
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    • These authors contributed equally to this study.

  • Anne Helfer,

    1. School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK,
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    • Present addresses:The Scripps Research Institute, Department of Cell Biology and Institute for Childhood and Neglected Diseases, La Jolla, CA 92037, USA;

    • These authors contributed equally to this study.

  • Elizabeth Hatzimasoura,

    1. School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK,
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  • Zoltán Magyar,

    1. School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK,
    2. Institute of Plant Biology, BRC, H-6701 Szeged, Hungary,
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  • Liliya Serazetdinova,

    1. Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, UK,
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  • Gabino Rios,

    1. Max-Planck Institut für Züchtungforschung, Carl-von-Linné-Weg 10, Köln, Germany, and
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  • Viola Bardóczy,

    1. Department of Biochemistry of Food Technology, Budapest University of Technology and Economics, Műegyetem rkp. 3, 1111 Budapest, Hungary,
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  • Markus Teige,

    1. Max F. Perutz Laboratories, Department of Biochemistry, University of Vienna, Vienna Biocentre, Dr Bohrgasse 9, A-1030 Vienna, Austria
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  • Csaba Koncz,

    1. Max-Planck Institut für Züchtungforschung, Carl-von-Linné-Weg 10, Köln, Germany, and
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  • Scott Peck,

    1. Sainsbury Laboratory, John Innes Centre, Norwich NR4 7UH, UK,
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    • §

      University of Missouri-Columbia, 271H Life Sciences Centre, Columbia, MO 65211, USA.

  • László Bögre

    Corresponding author
    1. School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK,
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*(fax +44 1784 434326; e-mail l.bogre@rhul.ac.uk).

Summary

Plants sense pathogens through both pathogen-associated molecular patterns and recognition of race-specific virulence factors, which induce basal defence or an accelerated defence (often manifest in the form of local cell death), respectively. A mitogen-activated protein kinase (MAPK) module in Arabidopsis was previously proposed to signal from perception of the bacterial elicitor flagellin to the activation of basal defence-related genes. Here, we present evidence for a parallel MAPK-signalling pathway involved in the response to flg22, a peptide corresponding to the most conserved domain of flagellin. The endogenous Arabidopsis MAP kinase kinase MKK1 is activated in cells treated with flg22, phosphorylates the MAPK MPK4 in vitro, and activates it in vivo in protoplasts. In mkk1 mutant plants, the activation by flg22 of MPK4 and two other flg22-induced MAPKs (MPK3 and MPK6) is impaired. In the mkk1 mutant, a battery of both flg22-induced and flg22-repressed genes show altered expression, indicating that MKK1 negatively regulates the activity of flagellin-responsive genes. Intriguingly, in contrast to the mpk4 mutant, mkk1 shows no morphological anomalies and is compromised in resistance to both virulent and avirulent Pseudomonas syringae strains. Thus, the MKK1 signalling pathway modulates the expression of genes responding to elicitors and plays an important role in pathogen defence.

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