Phosphorylation-dependent differential regulation of plant growth, cell death, and innate immunity by the regulatory receptor-like kinase BAK1

PLoS Genet. 2011 Apr;7(4):e1002046. doi: 10.1371/journal.pgen.1002046. Epub 2011 Apr 28.

Abstract

Plants rely heavily on receptor-like kinases (RLKs) for perception and integration of external and internal stimuli. The Arabidopsis regulatory leucine-rich repeat RLK (LRR-RLK) BAK1 is involved in steroid hormone responses, innate immunity, and cell death control. Here, we describe the differential regulation of three different BAK1-dependent signaling pathways by a novel allele of BAK1, bak1-5. Innate immune signaling mediated by the BAK1-dependent RKs FLS2 and EFR is severely compromised in bak1-5 mutant plants. However, bak1-5 mutants are not impaired in BR signaling or cell death control. We also show that, in contrast to the RD kinase BRI1, the non-RD kinases FLS2 and EFR have very low kinase activity, and we show that neither was able to trans-phosphorylate BAK1 in vitro. Furthermore, kinase activity for all partners is completely dispensable for the ligand-induced heteromerization of FLS2 or EFR with BAK1 in planta, revealing another pathway specific mechanistic difference. The specific suppression of FLS2- and EFR-dependent signaling in bak1-5 is not due to a differential interaction of BAK1-5 with the respective ligand-binding RK but requires BAK1-5 kinase activity. Overall our results demonstrate a phosphorylation-dependent differential control of plant growth, innate immunity, and cell death by the regulatory RLK BAK1, which may reveal key differences in the molecular mechanisms underlying the regulation of ligand-binding RD and non-RD RKs.

MeSH terms

  • Alleles
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / immunology*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Death*
  • Cloning, Molecular
  • Gene Expression Regulation, Plant
  • Hypocotyl / growth & development
  • Immunity, Innate
  • Phosphorylation
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / growth & development
  • Plants, Genetically Modified / immunology
  • Plants, Genetically Modified / metabolism
  • Point Mutation
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Reactive Oxygen Species / metabolism
  • Receptors, Pattern Recognition / genetics
  • Receptors, Pattern Recognition / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction*
  • Steroids / metabolism

Substances

  • Arabidopsis Proteins
  • EFR protein, Arabidopsis
  • Reactive Oxygen Species
  • Receptors, Pattern Recognition
  • Recombinant Fusion Proteins
  • Steroids
  • Protein Kinases
  • BAK1 protein, Arabidopsis
  • FLS2 protein, Arabidopsis
  • BRI1 protein, Arabidopsis
  • Protein-Serine-Threonine Kinases