LysM domains are conserved protein domains found in proteins of multiple organisms. This includes bacterial peptidoglycan-binding proteins, chitinases from yeast and algae and membrane-bound receptor-like kinases in plants. Several LysM encoding genes have also been identified in humans, where their function is unknown. Symbiotic interaction between legumes and rhizobia results in the development of a new organ, the root nodule. The specificity of the rhizobial/legume interaction is determined by LysM receptor-like kinases (NFR1/NFR5) and rhizobia secreted Nod factors containing strain specific decorations. The extracellular LysM domains of the NFR1 and NFR5 receptor kinases are believed to be responsible for perceiving the Mesorhizobium loti produced Nod factor in the epidermal root hair cells of Lotus japonicus. Several other genes encoding LysM containing proteins have been identified in the Lotus japonicus genome. A putative function for a number of these during development of symbiotic interactions has been hypothesised and is undergoing further investigation. This project is focusing on the establishment of a platform for in vitro expression and purification of the Nod factor receptors followed by a thorough investigation of the structural conformation of the proteins and the interaction with Nod factor. Various approaches will be taken to determine the kinetics of the interaction, i.e. the rates of complex formation (ka) and dissociation (kd). The proteins are expressed either in stable transformed Arabidopsis thaliana or in Nicotiana benthamiana leaves by Agrobacterium mediated transient gene expression. The goal of this project is to give us an understanding of the structural features of the LysM-RLKs that determine the specificity of the interaction between Mesorhizobium loti and Lotus japonicus.