title: Expression of the Sinorhizobium meliloti small RNA gene mmgR is controlled by the nitrogen source.
abstract: Small non-coding regulatory RNAs (sRNAs) are key players in post-transcriptional regulation of gene expression. Hundreds of sRNAs have been identified in Sinorhizobium meliloti, but their biological function remains unknown for most of them. In this study, we characterized the expression pattern of the gene encoding the 77-nt sRNA MmgR in S. meliloti strain 2011. A chromosomal transcriptional reporter fusion (PmmgR-gfp) showed that the mmgR promoter is active along different stages of the interaction with alfalfa roots. In pure cultures, PmmgR-gfp activity paralleled the sRNA abundance indicating that mmgR expression is primarily controlled at the level of transcriptional initiation. PmmgR-gfp activity was higher during growth in rhizobial defined medium (RDM) than in TY medium. Furthermore, PmmgR-gfp was induced at 60 min after shifting growing cells from TY to RDM medium, i.e. shorter than the cell doubling time. In defined RDM medium containing NO3 (-), both PmmgR-gfp and MmgR level were repressed by the addition of tryptone or single amino acids, suggesting that mmgR expression depends on the cellular nitrogen (N) status. In silico analysis failed to detect conserved motifs upstream the promoter RNA polymerase binding site, but revealed a strongly conserved motif centered at -28 that may be linked to the observed regulatory pattern by the N source.
authors.affiliation: Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina.
authors.forename: Germán
authors.initials: G
authors.lastname: Ceizel Borella
authors.affiliation: Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina.
authors.forename: Antonio
authors.initials: A
authors.lastname: Lagares
authors.affiliation: Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina cvalver@unq.edu.ar.
authors.forename: Claudio
authors.initials: C
authors.lastname: Valverde
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D003470:Culture Media / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D000455:Medicago sativa / Q000382:microbiology; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D010461:Peptones / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics*; D058727:RNA, Small Untranslated / Q000235:genetics*; D012231:Rhizobium / Q000737:chemistry; D016962:Sinorhizobium meliloti / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D014158:Transcription, Genetic
chemical_list: D000596:Amino Acids; D003470:Culture Media; D010461:Peptones; D012329:RNA, Bacterial; D058727:RNA, Small Untranslated; C001830:tryptones; D009584:Nitrogen
keywords: Riboregulation; Sinorhizobium meliloti; mmgR; nitrogen; promoter regulation; sRNA