title: Isolation and characterization of an ndvB locus from Rhizobium fredii.
abstract: A gene (ndvB) in Rhizobium meliloti that is essential for nodule development in Medicago sativa (alfalfa), specifies synthesis of a large membrane protein. This protein appears to be an intermediate in beta-1,2-glucan synthesis by the microsymbiont. Southern hybridization analysis showed strong homology between an ndvB (chvB) probe and genomic DNA of R. fredii but not from Bradyrhizobium japonicum. A cosmid clone containing the putative ndvB locus was isolated from a Rhizobium fredii gene library. The cosmid clone which complemented R. meliloti ndvB mutants for synthesis of beta-1,2-glucans and effective nodulation of alfalfa was mapped and subcloned. Fragment-specific Tn5 mutagenesis followed by homologous recombination into the R. fredii genome indicated that the region was essential for beta-1,2-glucan synthesis and for formation of an effective symbiosis with Glycine max (soybean).
authors.affiliation: Soybean and Alfalfa Research Laboratory, USDA, Agricultural Research Service, Beltsville, Maryland 20705-2350.
authors.forename: A A
authors.initials: AA
authors.lastname: Bhagwat
authors.forename: R E
authors.initials: RE
authors.lastname: Tully
authors.forename: D L
authors.initials: DL
authors.lastname: Keister
mesh_terms: D004269:DNA, Bacterial / Q000302:isolation & purification; D007887:Fabaceae / Q000382:microbiology*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005936:Glucans / Q000235:genetics; D016254:Mutagenesis, Insertional; D009586:Nitrogen Fixation; D010946:Plants, Medicinal; D012230:Rhizobiaceae / Q000235:genetics / Q000502:physiology; D012231:Rhizobium / Q000235:genetics* / Q000502:physiology; D017385:Sequence Homology; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000502:physiology; D013045:Species Specificity
chemical_list: D004269:DNA, Bacterial; D005936:Glucans