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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Nürnberger, T., Brunner, F., Kemmerling, B. & Piater, L. Innate immunity in plants and animals: striking similarities and obvious differences. Immunol. Rev. 198, 249–266 (2004)
Gómez-Gómez, L. & Boller, T. FLS2: an LRR receptor-like kinase involved in the perception of the bacterial elicitor flagellin in Arabidopsis. Mol. Cell 5, 1003–1011 (2000)
Zipfel, C. et al. Perception of the bacterial PAMP EF-Tu by the receptor EFR restricts agrobacterium-mediated transformation. Cell 125, 749–760 (2006)
Felix, G., Duran, J. D., Volko, S. & Boller, T. Plants have a sensitive perception system for the most conserved domain of bacterial flagellin. Plant J. 18, 265–276 (1999)
Kunze, G. et al. The N terminus of bacterial elongation factor Tu elicits innate immunity in Arabidopsis plants. Plant Cell 16, 3496–3507 (2004)
Li, J. et al. BAK1, an Arabidopsis LRR receptor-like protein kinase, interacts with BRI1 and modulates brassinosteroid signalling. Cell 110, 213–222 (2002)
Nam, K. H. & Li, J. BRI1/BAK1, a receptor kinase pair mediating brassinosteroid signalling. Cell 110, 203–212 (2002)
Janeway, C. A. & Medzhitov, R. Innate immune recognition. Annu. Rev. Immunol. 20, 197–216 (2002)
Zeidler, D. et al. Innate immunity in Arabidopsis thaliana: lipopolysaccharides activate nitric oxide synthase (NOS) and induce defense genes. Proc. Natl Acad. Sci. USA 101, 15811–15816 (2004)
Chinchilla, D., Bauer, Z., Regenass, M., Boller, T. & Felix, G. The Arabidopsis receptor kinase FLS2 binds flg22 and determines the specificity of flagellin perception. Plant Cell 18, 465–476 (2006)
Zipfel, C. et al. Bacterial disease resistance in Arabidopsis through flagellin perception. Nature 428, 764–767 (2004)
Vert, G., Nemhauser, J. L., Geldner, N., Hong, F. & Chory, J. Molecular mechanisms of steroid hormone signalling in plants. Annu. Rev. Cell Dev. Biol. 21, 177–201 (2005)
Kauschmann, A. et al. Genetic evidence for an essential role of brassinosteroids in plant development. Plant J. 9, 701–713 (1996)
Kinoshita, T. et al. Binding of brassinosteroids to the extracellular domain of plant receptor kinase BRI1. Nature 433, 167–171 (2005)
Russinova, E. et al. Heterodimerization and endocytosis of Arabidopsis brassinosteroid receptors BRI1 and AtSERK3 (BAK1). Plant Cell 16, 3216–3229 (2004)
Robatzek, S., Chinchilla, D. & Boller, T. Ligand-induced endocytosis of the pattern recognition receptor FLS2 in Arabidopsis. Genes Dev. 20, 537–542 (2006)
Felix, G., Grosskopf, D. G., Regenass, M. & Boller, T. Rapid changes of protein phosphorylation are involved in transduction of the elicitor signal in plant cells. Proc. Natl Acad. Sci. USA 88, 8831–8834 (1991)
Gómez-Gómez, L., Bauer, Z. & Boller, T. Both the extracellular leucine-rich repeat domain and the kinase activity of FSL2 are required for flagellin binding and signalling in Arabidopsis. Plant Cell 13, 1155–1163 (2001)
Massague, J. TGF-beta signal transduction. Annu. Rev. Biochem. 67, 753–791 (1998)
Schlessinger, J. Ligand-induced, receptor-mediated dimerization and activation of EGF receptor. Cell 110, 669–672 (2002)
Dardick, C. & Ronald, P. Plant and animal pathogen recognition receptors signal through non-RD kinases. PLoS Pathogens 2, e2 (2006)
Li, J. & Jin, H. Regulation of brassinosteroid signalling. Trends Plant Sci. 12, 37–41 (2007)
Wang, X. et al. Identification and functional analysis of in vivo phosphorylation sites of the Arabidopsis BRASSINOSTEROID-INSENSITIVE1 receptor kinase. Plant Cell 17, 1685–1703 (2005)
Kemmerling, B. et al. The BRI1-associated kinase 1, BAK1, has a brassinolide-independent role in plant cell-death control. Curr. Biol. doi: 10.1016/j.cub.2007.05.046 (published online 21 June 2007)
Hecht, V. et al. The Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR KINASE 1 gene is expressed in developing ovules and embryos and enhances embryogenic competence in culture. Plant Physiol. 127, 803–816 (2001)
Colcombet, J., Boisson-Dernier, A., Ros-Palau, R., Vera, C. E. & Schroeder, J. I. Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR KINASES1 and 2 are essential for tapetum development and microspore maturation. Plant Cell 17, 3350–3361 (2005)
Albrecht, C., Russinova, E., Hecht, V., Baaijens, E. & de Vries, S. The Arabidopsis thaliana SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASES1 and 2 control male sporogenesis. Plant Cell 17, 3337–3349 (2005)
Karlova, R. et al. The Arabidopsis SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1 protein complex includes BRASSINO STEROID-INSENSITIVE1. Plant Cell 18, 626–638 (2006)
Lemaitre, B., Nicolas, E., Michaut, L., Reichhart, J. M. & Hoffmann, J. A. The dorsoventral regulatory gene cassette spatzle/Toll/cactus controls the potent antifungal response in Drosophila adults. Cell 86, 973–983 (1996)
Alonso, J. M. et al. Genome-wide insertional mutagenesis of Arabidopsis thaliana. Science 301, 653–657 (2003)
Hellens, R. P., Edwards, E. A., Leyland, N. R., Bean, S. & Mullineaux, P. M. pGreen: a versatile and flexible binary Ti vector for Agrobacterium-mediated plant transformation. Plant Mol. Biol. 42, 819–832 (2000)
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.
Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.
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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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