title: Rhizobial factors required for stem nodule maturation and maintenance in Sesbania rostrata-Azorhizobium caulinodans ORS571 symbiosis.
abstract: The molecular and physiological mechanisms behind the maturation and maintenance of N(2)-fixing nodules during development of symbiosis between rhizobia and legumes still remain unclear, although the early events of symbiosis are relatively well understood. Azorhizobium caulinodans ORS571 is a microsymbiont of the tropical legume Sesbania rostrata, forming N(2)-fixing nodules not only on the roots but also on the stems. In this study, 10,080 transposon-inserted mutants of A. caulinodans ORS571 were individually inoculated onto the stems of S. rostrata, and those mutants that induced ineffective stem nodules, as displayed by halted development at various stages, were selected. From repeated observations on stem nodulation, 108 Tn5 mutants were selected and categorized into seven nodulation types based on size and N(2) fixation activity. Tn5 insertions of some mutants were found in the well-known nodulation, nitrogen fixation, and symbiosis-related genes, such as nod, nif, and fix, respectively, lipopolysaccharide synthesis-related genes, C(4) metabolism-related genes, and so on. However, other genes have not been reported to have roles in legume-rhizobium symbiosis. The list of newly identified symbiosis-related genes will present clues to aid in understanding the maturation and maintenance mechanisms of nodules.
authors.affiliation: Biotechnology Research Center, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Shino
authors.initials: S
authors.lastname: Suzuki
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aono
authors.forename: Kyung-Bum
authors.initials: KB
authors.lastname: Lee
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Suzuki
authors.forename: Chi-Te
authors.initials: CT
authors.lastname: Liu
authors.forename: Hiroki
authors.initials: H
authors.lastname: Miwa
authors.forename: Seiji
authors.initials: S
authors.lastname: Wakao
authors.forename: Taichiro
authors.initials: T
authors.lastname: Iki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Oyaizu
mesh_terms: D020583:Azorhizobium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D007887:Fabaceae / Q000254:growth & development / Q000382:microbiology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D009586:Nitrogen Fixation; D018547:Plant Stems / Q000378:metabolism / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements