LORE homomerization is required for 3-OH-C10:0 induced immune signaling

Abstract

ABSTRACTPerception and processing of various internal and external signals is essential for all living organisms. Plants have an expanded and diversified repertoire of cell surface-localized receptor-like kinases (RLKs) that transduce signals across the plasma membrane. RLKs often assemble into higher-order receptor complexes with co-receptors, regulators and scaffolds to convert extracellular stimuli into cellular responses. To date, the only S-domain-RLK from Arabidopsis thaliana with a known ligand and function is AtLORE, a pattern recognition receptor that senses bacterial 3-hydroxy fatty acids of medium chain length, such as 3-hydroxy decanoic acid (3-OH-C10:0), to activate pattern-triggered immunity. Here we show that AtLORE forms receptor homomers, which is essential for 3-OH-C10:0-induced immune signaling. AtLORE homomerization is mediated by the transmembrane and extracellular domain. We show natural variation in the perception of 3-OH-C10:0 within the Brassicaceae family. Arabidopsis lyrata and Arabidopsis halleri do not respond to 3-OH-C10:0, although they possess a putative LORE orthologue. We found that LORE orthologues of these 3-OH-C10:0 nonresponsive species have defective extracellular domains that can bind the 3-OH-C10:0 ligand but lack the ability to homomerize. Our findings shed light on the activation mechanisms of AtLORE and explain natural variation of 3-OH-C10:0 perception within the Brassicaceae family.