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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-090 - The Medicago LYR4 Receptor specifically recognizes long Chitin Chains and serves as a Scaffold for downstream Immune Signaling

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Extracellular & Intracellular non-self recognition & signaling

    Presenting Author(s)

  • HR

    Henriette Ruebsam

    Faculty of Biology, University of Freiburg
    Freiburg, Baden-Wurttemberg, Germany

    • Author(s)

  • BS

    Bine Simonsen

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • KG

    Kira Gysel

    Assistant Professor
    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • SH

    Simon B. Hansen

    Department of Molecular Biology and Genetics, Aarhus University
    Zürich, Zurich, Switzerland

  • MV

    Marie Vogel Kolte

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • MM

    Maria Meisner Larsen

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • CK

    Christina Kroenauer

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • MV

    Maria Vinther

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • JS

    Jens Stougaard

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • SR

    Simona Radutoiu

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

  • KA

    Kasper Andersen

    Department of Molecular Biology and Genetics, Aarhus University
    Aarhus, Midtjylland, Denmark

Plants perceive chitin derived from fungal cell walls through lysin motif (LysM) receptor kinases. In the model legume Medicago truncatula, the active kinase receptor CERK1 and the pseudokinase receptor LYR4 play crucial roles in chitin-triggered immunity signaling. Previous studies indicated size-selectivity in chitin perception, but the molecular basis remained unclear. We identified an additional N-terminal domain in the crystal structure of the LYR4 ectodomain, which enables the specific recognition of long chitin chains. Furthermore, structural and biochemical characterization of the LYR4 intracellular domain revealed phosphorylation activity despite the absence of canonical kinase features. Through binding studies and in planta experiments we demonstrated that LYR4 is the primary chitin binder in Medicago, but that reactive-oxygen species production is independent of its catalytic activity. We conclude that LYR4 rather serves as a scaffold for downstream signaling components and likely forms a complex with CERK1 upon chitin binding. These findings provide a mechanistic understanding of how plants specifically respond to chitin and initiate an immune response.