earticle

영어

The soil bacterium Bradyrhizobium japonicum induces nodulation on the soybean root, resulting in formation of root nodules where bacteria fix atmosphereic nitrogen into ammonia. Rhizobial lipopolysaccharides (LPS) have been known to be an important factor for initiating and maintaining a symbiotic relationship with their host. In previous studies, a LPS gene region was isolated from B .japonicum strain 61A101C. In this study, we have selected one of the genes whose sequence is highly homologous to lpcC gene, encoding mannosyl transferase. We constructed lpcC knock out mutant to characterize the functions of the lpcC gene in B. japonicum. The lpcC null mutant showed distinct phenotypes from the wild type. The mutant failed to elicit nodules through in vivo plant nodulation test. To examine if LPS deficient mutant becomes sensitive to plant derived defense substance, especially to reactive oxygen species (ROS), wild type and the mutant strains were challenged with hydrogen peroxide at concentrations of 10-15μM. The mutant exhibited a significantly increased sensitivity to hydrogen peroxide. Further studies on the relationship between plant defense mechanism and nodulation are required.