rosR, a determinant of nodulation competitiveness in Rhizobium etli

Mol Plant Microbe Interact. 1997 Mar;10(2):180-6. doi: 10.1094/MPMI.1997.10.2.180.


We previously described a Tn5 mutant of Rhizobium etli strain CE3, designated CE3003, that is decreased in nodulation competitiveness, reduced in competitive growth in the rhizosphere, and has a hydrophobic cell surface (R. S. Araujo, E. A. Robleto, and J. Handelsman, Appl. Environ. Microbiol., 60:1430-1436, 1994). To determine the molecular basis for the mutant phenotypes, we identified a 1.2-kb fragment of DNA derived from the parent that restored the wild-type phenotypes to the mutant. DNA sequence analysis indicated that this 1.2-kb fragment contained a single open reading frame that we designated rosR. The Tn5 insertion in CE3003 was within rosR. We constructed a derivative of CE3 that contained a deletion in rosR, and this mutant was phenotypically indistinguishable from CE3003 in cell surface and competitive characteristics. Based on the nucleotide sequence, the deduced RosR amino acid sequence is 80% identical to that of the Ros protein from Agrobacterium tumefaciens and the MucR protein from Rhizobium meliloti. Both Ros and MucR are transcriptional repressors that contain a putative zinc-finger DNA-binding domain. This study defines a gene, rosR, that is homologous to a family of transcriptional regulators and contributes to nodulation competitiveness of R. etli. Moreover, we established that a single gene affects nodulation competitiveness, competitive growth in the rhizosphere, and cell surface hydrophobicity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins*
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers / genetics
  • DNA-Binding Proteins / genetics*
  • Fabaceae / microbiology*
  • Genes, Bacterial*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutation
  • Phenotype
  • Plants, Medicinal*
  • Repressor Proteins / genetics*
  • Rhizobium / genetics*
  • Sequence Homology, Amino Acid


  • Bacterial Proteins
  • DNA Primers
  • DNA-Binding Proteins
  • Repressor Proteins

Associated data

  • GENBANK/U61146