Identification and characterization of a Rhizobium leguminosarum bv. phaseoli gene that is important for nodulation competitiveness and shows structural homology to a Rhizobium fredii host-inducible gene

Mol Plant Microbe Interact. May-Jun 1995;8(3):468-72. doi: 10.1094/mpmi-8-0468.


DNA sequence analysis of a 1.4-kb SalI-HindIII segment located approximately 2 kb upstream of the Rhizobium leguminosarum bv. phaseoli syrM gene revealed the presence of an open reading frame (ORF3) encoding a putative 295-amino acid polypeptide with a molecular mass of 33,401 Da. ORF3 is homologous to a R. fredii host-inducible gene. The proteins encoded by R. l. bv. phaseoli ORF3 and by the R. fredii host-inducible gene share 37% sequence identity. In contrast to the R. fredii host-inducible gene, expression of ORF3 is not induced in the presence of Phaseolus vulgaris root exudates or by specific flavonoids, able to induce nodulation genes in R. l. bv. phaseoli. A R. l. bv. phaseoli ORF3 mutant was constructed by site-directed deletion/replacement mutagenesis. This mutant strain is not affected in symbiotic nitrogen fixation but exhibits a delay in nodulation on Phaseolus vulgaris. Moreover, this mutant was shown to be defective in competition for nodulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / physiology
  • Base Sequence
  • DNA, Bacterial
  • Genes, Bacterial*
  • Molecular Sequence Data
  • Nitrogen Fixation / genetics*
  • Rhizobium / genetics*
  • Rhizobium leguminosarum / genetics*
  • Sequence Homology, Amino Acid


  • 33.4-kDa protein, Rhizobium
  • Bacterial Proteins
  • DNA, Bacterial