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Poster

Session: Session 1 Presenting Authors at Posters (Odds)

P-079 - Structural and biochemical basis of activation and autoinhibition of an NLR immune receptor network

Monday, July 14, 2025
13:30 - 15:15  
Location: Confex Hall 3
Extracellular & Intracellular non-self recognition & signaling

Plant immune systems rely on intracellular nucleotide-binding domain and leucine-rich repeat (NLR) receptors to detect and respond to pathogen-secreted effectors. While structural studies of the Arabidopsis NLR ZAR1 have advanced our understanding of NLR activation, most insights come from singleton NLRs that function independently. Many NLRs operate in higher-order pairs or networks, and their structural mechanisms of activation remain poorly characterized. To address this, we developed IP-EM, a Nicotiana benthamiana-based protein purification pipeline, and applied it to the NRC network, a hierarchical solanaceous NLR immune receptor network that connects sensor NLRs and cell-surface receptors to helper NLRs of the NRC clade. Unlike ZAR1, we find that resting state NRC2 helpers exist as homodimers and filaments prior to activation. Pathogen perception by upstream sensor NLRs triggers structural rearrangements that allows them to signal via their central nucleotide-binding (NB) to their downstream NRC helpers. This initiates NRC2 conversion from dimers and filaments into hexameric resistosomes, which accumulate at the plasma membrane, spatially separate from the sensor NLRs that activated them. This mechanism is structurally and biochemically distinct from ZAR1, revealing new principles of NLR activation in plants. Expanding structural studies beyond singleton NLRs is be essential to uncover the full diversity of immune receptor mechanisms and their roles in plant defense.