title: nif gene expression in a Nif+, Fix- Bradyrhizobium japonicum variant.
abstract: Bradyrhizobium japonicum USDA 110 has been shown to contain several genetically similar, naturally occurring colony morphology variants. One of these variants, L2-110, although devoid of symbiotic nitrogen fixation, retains significant levels of ex planta nitrogen fixation ability relative to other symbiotically competent USDA 110 variants (MN-110 and I-110). Interestingly, Northern blot analyses revealed that L2-110 nodules, despite their lack of symbiotic nitrogen fixation, contained 65% the level of mRNA for dinitrogenase (nif DK) and 64% the level of dinitrogenase reductase (nif H) mRNA relative to MN-110 nodules. Western blot analyses of tissue from the same nodules detected 32% the level of dinitrogenase and 31% the level of dinitrogenase reductase in L2-110 relative to MN-110. L2-110 appears to be a new class of mutant based on the complete absence of symbiotic nitrogen fixation (Fix-) and the presence of significant ex planta nitrogen fixation (Nif+).
authors.affiliation: School of Biology, Georgia Institute of Technology, Atlanta.
authors.forename: J A
authors.initials: JA
authors.lastname: Bradburne
authors.forename: J N
authors.initials: JN
authors.lastname: Mathis
authors.forename: D W
authors.initials: DW
authors.lastname: Israel
mesh_terms: D017037:Dinitrogenase Reductase / Q000096:biosynthesis*; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics; D009591:Nitrogenase / Q000096:biosynthesis*; D012230:Rhizobiaceae / Q000235:genetics*
chemical_list: D017037:Dinitrogenase Reductase; D009591:Nitrogenase