Abstract
Lipopolysaccharide (LPS) of Gram negative bacteria is recognized by plants as one of the PAMPs (Pathogen Associated Molecular Patterns) and is also involved in establishing normal symbiosis between rhizobia and their host legumes. However, the recognition mechanism is still not clear in plants. LPS binding protein (LBP) forms a complex with LPS and activates innate immune system in animals. On the genome of Lotus japonicus, four genes, LjLBP1, 2, 3 and 4, were identified as candidates for plant LBP and their expression were analyzed with or without microsymbiont Mesorhizobium loti. Among the LBPs, LjLBP3/4 was up-ragulated transiently at 4h after inoculation of M. loti. However, the expression ofLjLBP3/4 was strongly repressed in nodulated plants compared with that of plant supplied with 0.5 mM NH4Cl. These results indicate that the expression of each LBP is regulated in different manner depending on the stage of the symbiosis. Considering with the symbiotic phenotype of LBP mutant lines of L. japonicus, LBPs will be involved in legume-Rhizobium symbiosis.
