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Novel strategies for crop improvement and protection aim at enhancing host recognition capacities for potential pathogens, at interfering with virulence strategies employed by microbial pathogens or at taking advantages of natural symbioses. Implementation of such technologies requires substantial advances in our understanding of the molecular mechanisms governing plant-microbe interactions. Plant lysin motif (LysM) domain receptors have evolved to recognize microbe-derived Nacetylglucosamine (NAG)-containing ligands. For example, LysM-type immune receptors mediate sensing of microbe-derived patterns chitin or peptidoglycan thereby mediating plant immunity to fungal or bacterial infection, respectively. Likewise, recognition by plant LysM-type receptors of microbe-derived NAG-containing lipo-chitooligosaccharides establishes root symbioses between host plants and soil borne rhizobacteria or mycorrhizal fungi. Plant pathogenic microbes have further been shown to employ LysM-type effector proteins to subvert plant immunity. It is thus most reasonable to assume that a sophisticated mechanistic understanding of the architecture, the mode of assembly and of structural features determining ligand specificity of LysM proteins holds great promise for modulating plant-microbe interactions and for enhancing crop quality in the future. The proposed research consortium brings together five European Partners with longstanding and complementary experience in exploring the functionality of LysM domain proteins implicated in plant symbiosis and immunity. The experimental systems to be used comprise Arabidopsis thaliana immune receptors AtCERK1 (chitin sensor), AtLYM1/AtLYM3 (peptidoglycan sensors) and AtLysM2, Lotus japonicus nodulation factor sensors LjNFR1 and LjNFR5, and Cladosporium fulvum CfECP6 and Mycosphaerella graminicola LysM effectors (chitin or chitin/peptidoglycan sensors). The proposed work plan serves ERA-CAPS themes 'Biotic Stress' and 'Food Security' and comprises four objectives: (I) Elucidation of the structural determinants within LysM proteins that govern ligand specificities and affinities by means of protein X-ray analysis and comprehensive analysis of LysM protein ligand affinity measurements, (II) LysM receptor-ligand complex architecture and stoichiometry analysis by advanced biochemical and protein microscopical techniques, (III) Molecular analyses of LysM receptor-mediated transmembrane signaling, intra- and intercellular signal generation by means of state-of-the-art biochemical and genetic approaches, and (IV) Exploitation of 3D-structural information of LysM receptors for computational drug design strategies that aim at isolating agonists of plant immunity. |