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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-028 - Dissecting the functional principles of plant Receptor-Like Protein (RLP) ligand binding and immune signalling

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Extracellular & Intracellular non-self recognition & signaling
Plant immune recognition of pests and pathogens relies on a diverse repertoire of innate immune receptors. Receptor-like proteins (RLPs) are surface-localised receptors that bind pathogen-associated molecules and initiate a specific immune response. All known immunity-related RLPs require co-receptor SOBIR1 to induce defences. However, the recognition and signalling mechanisms of RLPs remain poorly understood. The recently proposed ‘loop model’ of RLP activation, based on cryo-EM and crystal structures of N. benthamiana LRR-RLP RXEG1, identifies two key loop-out subdomains (loop1 and loop2) of LRRs that mediate ligand binding and co-receptor recruitment. Furthermore, AlphaFold2-multimer (AF2) modelling predicts the presence of these loops in most known defense-related RLPs. Here, we aim to dissect the specificity determinants of ligand binding and downstream signalling of canonical tomato RLP Cf-4. We show that loop1 and loop2 are necessary for recognition and binding of cognate effector Avr4 using hypersensitive response (HR) cell-death assays and co-immunoprecipitation (co-IP) assays. Additionally, we use AF modelling and HR assays to pinpoint specific residues in the tail domain of Cf-4 that are required for initiating HR cell-death. These findings contribute to a detailed understanding of RLP mode of action that is necessary for the rational design and bioengineering of novel immune receptors with enhanced recognition specificity and robust disease resistance.