MOB proteins as novel regulators of pathogen-associated molecular pattern-triggered immunity in Arabidopsis thaliana

• Applicant: Professor Dr. Martin Stegmann
• Subject Area: Plant Biochemistry and Biophysics ; Plant Genetics and Genomics
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 271734448

• Final Report Year: 2018

Final Report Abstract

Identification and characterization of the mob6 mutant resulted in the discovery of a new signalling pathway of how plants control the formation of signalling competent receptor complexes during innate immunity by the interplay of the FER receptor kinase with some of its endogenous RALF peptide ligands. The two best studied immune receptors for the detection of invading microbes are FLS2 and EFR, which both form ligand-induced complexes with their co-receptor BAK1. We could show that formation of a signalling competent FLS2- BAK1 and EFR-BAK1 complex requires the malectin-receptor kinase FER. To regulate steady-state FER function, the receptor is most likely in a state where it binds to immunestimulatory RALF peptides, such as RALF17. In response to PAMP perception by either FLS2 or EFR, a negative feedback loop is initiated, which results in the activation of the S1P protease, which subsequently releases immunosuppressive RALF peptides, such as RALF23, from its precursor propeptide. RALF23 in turn inhibits the scaffolding function of FER, resulting in the inhibition of FLS2-BAK1 and EFR-BAK1 complex formation. FER is involved in a plethora of physiological responses, many of which require ligand-induced receptor complexes for signal initiation. We thus hypthosesize that FER-mediated regulation of other signalling pathways underlies a similar mechanistic concept.

Publications

• The apoplast as battleground for plant-microbe interactions. New Phytol. 209, 34–38 (2016)
  Y. Du, M. Stegmann, J. C. Misas Villamil
  
• Complex regulation of plant sex by peptides. Science (80). 358, 1544–1545 (2017)
  M. Stegmann, C. Zipfel
  
• The receptor kinase FER is a RALF-regulated scaffold controlling plant immune signaling. Science (80)4, 287–289 (2017)
  M. Stegmann, J. Monaghan, E. Smakowska-Luzan, H. Rovenich, A. Lehner, N. Holton, Y. Belkhadir, C. Zipfel
  
• An extracellular network of Arabidopsis leucine-rich repeat receptor kinases. Nature. 553, 342 (2018)
  E. Smakowska-Luzan, A. G. Mott, K. Parys, M. Stegmann, T. Howton, M. Layeghifard, J. Neuhold, A. Lehner, J. Kong, K. Gruenwald, N. Weinberger, S. B. Satbhai, D. Mayer, W. Busch, M. Madalinski, P. Stolt-Bergner, N. J. Provart, S. M. Nukhtar, C. Zipfel, D. Desveaux, D. S. Guttman, Y. Belkhadir