Abstract
Legumes are able to establish a symbiosis with rhizobium bacteria. Recognition of the rhizobial Nod Factors (NFs) is crucial to initiate symbiotic process in legume plants. Structural backbone of NFs is N-acylated chitin oligomer. Chitin oligomers are known as elicitors which induce defense responses in many plant species. NFs and chitin elicitors have been shown to be recognized by closely-related LysM receptor kinases. We focus on the mechanisms controlling these opposite responses elicited by the similar molecules.
Microarray analyses using a model legume Lotus japonicus indicated that the genes involved in defense responses such as phytoalexin synthesis were drastically up-regulated by NFs as well as chitin treatment. NF-induced, but not chitin-induced, defense gene expression was abolished in nfr1 mutant. In-gel kinase assay revealed that SIPK and WIPK-like activities were induced in NF-treated roots.
