Abstract
Establishment of legume-rhizobium symbiosis requires a series of mutual authentications, which is believed to include bacterial evasion of host defense. One of such evasion-related genes is bacA in Sinorhizobium meliloti that had been identified as a gene essential for bacteroid formation after invasion into host cytoplasm. Although bacA homologue in the animal pathogen Brucella abortus was shown to be important for survival in host macrophage, homologues in rhizobia other than S. meliloti have been less studied. We have initiated genetic studies of genome region around bacA homologue, mlr7400, in Mesorhizobium loti that is a microsymbiont of determinative model legume, Lotus japonicus. Both mini-transposon mutagenesis and targeted gene deletion indicated that mlr7400 mutants of M. loti display less severe defects in symbiotic capacity than bacA mutants of S. meliloti. The milder phenotype of the M. loti mutants was also supported by almost no increased sensitivity against ethanol and SDS.
