Molecular studies on a new genetic locus linked to the common nodulation genes in Bradyrhizobium japonicum.
ORFA, an actively transcribed genetic locus linked to the common nodulation genes in Bradyrhizobium japonicum USDA110, was sequenced and analysed. The expression of ORFA is neither dependent on the regulatory proteins NifA, NtrC, NtrB and NodD1 nor on either copy of sigma 54, RpoN1 and RpoN2. The transcriptional start site of ORFA was determined and found to overlap the oppositely transcribed nodZ gene by 224 nucleotides. An appropriately located -10 sequence identical to the consensus proposed for rhizobia and a homologous -35 region were identified upstream of the transcriptional start site. ORFA showed no significant homologies to known sequences in gene databases, and its mutational inactivation had no effect on the nodulation of five legume species. Nevertheless, ORFA seems to be conserved among bradyrhizobia, since an ORFA probe hybridised to total DNA extracted from other Bradyrhizobium strains.
Luka
S
S
Department of Microbiology, University of Tennessee, Knoxville 37996-0845, USA. s.luka@agora.stm.it
Stacey
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G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D002874:Chromosome Mapping; D005647:Fucosyltransferases / Q000235:genetics*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D012231:Rhizobium / Q000235:genetics*; D013559:Symbiosis; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D005647:Fucosyltransferases; C103941:NodZ protein, bacteria