title: Identification and characterization of a gene on Rhizobium meliloti pSyma, syrB, that negatively affects syrM expression.
abstract: The Rhizobium meliloti SyrM protein activates transcription of nodD3 and syrA. Regulation of syrM is complex and may involve as yet undiscovered genes. Here we report the isolation of insertion mutants showing increased expression of a syrM-gusA gene fusion. Characterization of one mutant strain, designated SYR-B, revealed a mutation consisting of a transposon insertion linked to a large deletion. The corresponding wild-type DNA was cloned as a 5.3-kb BamHI fragment. Genetic and physical analysis of this DNA demonstrated that an open reading frame (ORF) near one end of the fragment, encoding the 16.5-kDa SyrB protein, is responsible for the repression of syrM activity. Results of complementation experiments with the 5.3-kb BamHI DNA led us to hypothesize that other genes within this DNA fragment interfere with the expression or activity of SyrB. Our analysis showed that the region upstream of syrB contains three ORFs. One ORF is similar to the Ros repressor of Agrobacterium tumefaciens and the MucR repressor of R. meliloti.
authors.affiliation: Department of Biological Sciences, Stanford University, CA 94305, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Barnett
authors.forename: S R
authors.initials: SR
authors.lastname: Long
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins; D007887:Fabaceae / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D010453:Peptide Synthases; D010641:Phenotype; D010946:Plants, Medicinal; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D016962:Sinorhizobium meliloti / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C064814:SyrM protein, Rhizobium meliloti; D015534:Trans-Activators; D010453:Peptide Synthases; C094581:SYRB1 protein, Pseudomonas syringae