Characterization of the Rhizobium leguminosarum genes nodLMN involved in efficient host-specific nodulation.
Three nodulation genes, nodL, nodM and nodN, were isolated from Rhizobium leguminosarum and their DNA sequences were determined. The three genes are in the same orientation as the previously described nodFE genes and the predicted molecular weights of their products are 20,105 (nodL), 65,795 (nodM) and 18,031 (nodN). Analysis of gene regulation using operon fusions showed that nodL, nodM and nodN are induced in response to flavanone molecules and that this induction is nodD-dependent. In addition, it was shown that the nodM and nodN genes are in one operon which is preceded by a conserved 'nod-box' sequence, whereas the nodL gene is in the same operon as the nodFE genes. DNA hybridizations using specific gene probes showed that strongly homologous genes are present in Rhizobium trifolii but not Rhizobium meliloti or Bradyrhizobium japonicum. A mutation within nodL strongly reduced nodulation of peas, Lens and Lathyrus but had little effect on nodulation of Vicia species. A slight reduction in nodulation of Vicia hirsuta was observed with strains carrying mutations in nodM or nodN.
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics*; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000235:genetics*; D010957:Plasmids; D012231:Rhizobium / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D010940:Plant Proteins