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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-084 - Structural basis of effector-triggered immunity signalling activation by the flax M receptor

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

    Presenting Author(s)

  • NM

    Natsumi Maruta

    School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre and the Institute for Molecular Bioscience, The University of Queensland
    Brisbane, Queensland, Australia

    • Author(s)

  • MS

    Mitchell Sorbello (he/him/his)

    The University of Queensland
    Brisbane, Queensland, Australia

  • BL

    Bryan Ying Jie Lim

    School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre and the Institute for Molecular Bioscience, The University of Queensland
    Brisbane, Queensland, Australia

  • WG

    Weixi Gu

    The University of Queensland
    Brisbane, Queensland, Australia

  • DN

    Dalton Heng Yong Ngu

    School of Chemistry and Molecular Biosciences, Australian Infectious Diseases Research Centre and the Institute for Molecular Bioscience, The University of Queensland
    Brisbane, Queensland, Australia

  • JC

    Jian Chen

    CSIRO
    Canberra, Australian Capital Territory, Australia

  • HX

    Hongyi Xu

    Research School of Chemistry, The Australian National University
    Canberra, Australian Capital Territory, Australia

  • HB

    Hayden Burdett

    Wellcome Centre for Cell Biology, University of Edinburgh
    Edinburgh, Scotland, United Kingdom

  • SW

    Simon J. Williams, PhD (he/him/his)

    The Australian National University
    Canberra, Australian Capital Territory, Australia

  • PD

    Peter Dodds, PhD

    CSIRO Agriculture and Food
    Canberra, ACT, AUSTRALIA

  • BK

    Bostjan Kobe

    The University of Queensland
    Brisbane, Queensland, Australia

NLRs (nucleotide-binding leucine-rich repeat receptors) are essential for plants to recognise secreted pathogen effector proteins and activate effector-triggered immunity. NLRs typically consist of an N-terminal signalling domain, a central NB-ARC (nucleotide-binding) domain and a C-terminal LRR (leucine-rich repeat) domain. TIR (Toll/interleukin-1 receptor) domains hydrolyze NAD+ (nicotinamide adenine dinucleotide) to generate metabolites required for immune signalling. Previous studies demonstrated tetrameric resistosome structures of TNLs (TIR-NLRs) with the C-JID (C-terminal jellyroll/Ig-like domain) bound to effectors. To further characterize TNL activation and signalling mechanisms, we determined the cryo-EM structure of the flax M tetrameric resistosome, which is a non-C-JID type TNL. Each M protomer directly interacts with a monomer of its AvrM-A effector, through multiple LRR motifs and a NB-ARC subdomain. Structure-guided mutagenesis validates AvrM-A homodimer dissociation into monomers upon M recognition. We also demonstrate how MTIR domains bind to a non-hydrolyzable NAD+ analogue. M exhibits NADase activity but generates different signalling compounds from the related flax TNL L6. Cryo-EM analysis of inactive monomeric M shows a closed conformation. Our findings provide insights into the activation mechanism of TNL signalling and provide a basis for rational engineering of disease resistant crops.