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A flagellin-induced complex of the receptor FLS2 and BAK1 initiates plant defence

Nature volume 448, pages 497–500 (2007)Cite this article

Abstract

Plants sense potential microbial invaders by using pattern-recognition receptors to recognize pathogen-associated molecular patterns (PAMPs)1. In Arabidopsis thaliana, the leucine-rich repeat receptor kinases flagellin-sensitive 2 (FLS2) (ref. 2) and elongation factor Tu receptor (EFR) (ref. 3) act as pattern-recognition receptors for the bacterial PAMPs flagellin4 and elongation factor Tu (EF-Tu) (ref. 5) and contribute to resistance against bacterial pathogens. Little is known about the molecular mechanisms that link receptor activation to intracellular signal transduction. Here we show that BAK1 (BRI1-associated receptor kinase 1), a leucine-rich repeat receptor-like kinase that has been reported to regulate the brassinosteroid receptor BRI1 (refs 6,7), is involved in signalling by FLS2 and EFR. Plants carrying bak1 mutations show normal flagellin binding but abnormal early and late flagellin-triggered responses, indicating that BAK1 acts as a positive regulator in signalling. The bak1-mutant plants also show a reduction in early, but not late, EF-Tu-triggered responses. The decrease in responses to PAMPs is not due to reduced sensitivity to brassinosteroids. We provide evidence that FLS2 and BAK1 form a complex in vivo, in a specific ligand-dependent manner, within the first minutes of stimulation with flagellin. Thus, BAK1 is not only associated with developmental regulation through the plant hormone receptor BRI1 (refs 6,7), but also has a functional role in PRR-dependent signalling, which initiates innate immunity.

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Figure 1: bak1 mutants show reduced sensitivity to flagellin in growth assays.
Figure 2: bak1 mutants are impaired in responsiveness to flagellin and EF-Tu.
Figure 3: Flg22 binding sites are unaffected in bak1 mutants.
Figure 4: FLS2 rapidly interacts with BAK1 in a ligand-dependent manner.

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Acknowledgements

We thank A. Bent and V. Lipka for critically reading the manuscript; S. Salomon and A. Caniard for technical help; and the Salk Institute Genomic Analysis Laboratory (SIGnAL) and the NASC stock center for the T-DNA insertion lines and cbb1 seeds. This work was supported by the Swiss National Foundation and the European Molecular Biology Organization.

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Authors and Affiliations

  1. Zurich-Basel Plant Science Center, Botanical Institute, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland,

    Delphine Chinchilla, Cyril Zipfel, Silke Robatzek, Georg Felix & Thomas Boller

  2. The Sainsbury Laboratory, Colney Lane, Norwich, Norfolk NR4 7UH, UK,

    Cyril Zipfel & Jonathan D. G. Jones

  3. Max-Planck-Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany,

    Silke Robatzek

  4. Institute of Plant Biochemistry, ZMBP, University of Tuebingen, 72076 Tuebingen, Germany,

    Birgit Kemmerling, Thorsten Nürnberger & Georg Felix

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  1. Delphine Chinchilla
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Correspondence to Delphine Chinchilla or Thomas Boller.

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Chinchilla, D., Zipfel, C., Robatzek, S. et al. A flagellin-induced complex of the receptor FLS2 and BAK1 initiates plant defence. Nature 448, 497–500 (2007). https://doi.org/10.1038/nature05999

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