Shu, L.-J.; Schoenberger, L.; Ziffermayer, L.; Yu, F.-Y.; Deslandes-Herold, G.; Schmid, C.; Gigl, M.; Schaeffer, M.; Dawid, C.; Ranf, S.

Pattern recognition receptors are often conserved across plant lineages, yet how ligand sensing diversifies during evolution remains poorly understood. The receptor kinase LORE mediates Arabidopsis thaliana immune responses to bacterial medium-chain 3-hydroxy fatty acids (mc-3-OH-FAs), but its distribution and functional variation across Brassicaceae remain largely unexplored. We combined phylogenetic analysis, species-wide immune profiling, ligand-binding assays, heterologous functional testing, and A. thaliana lore-1 complementation to define LORE diversification across Brassicaceae. LORE orthologs with conserved 3-OH-C10:0 binding are present in all major Brassicaceae lineages, including the basal lineage. Functional complementation confirmed mc-3-OH-FA-sensing capacity in orthologs spanning all four lineages. By contrast, chain-length preference profiles among mc-3-OH-FAs varied between species and orthologs, ranging from narrow 3-OH-C10:0-dominated profiles to broader profiles with comparable sensitivity to 3-OH-C10:0 and 3-OH-C12:0. 3-OH-FA profiling of a diverse collection of plant-associated bacteria revealed that high levels of mc-3-OH-FAs are prevalent in Proteobacteria, and that the range of mc-3-OH-FA chain lengths produced corresponds to the chain-length preferences of Brassicaceae LORE receptors. Our results establish LORE as a Brassicaceae-restricted pattern recognition receptor with conserved mc-3-OH-FA sensing but diversified chain-length preferences, and provide an evolutionary framework for studying how ligand preference can diversify within a biologically relevant ligand spectrum while core receptor function is maintained.