title: Characterization of the NifA-RpoN regulon in Rhizobium etli in free life and in symbiosis with Phaseolus vulgaris.
abstract: The NifA-RpoN complex is a master regulator of the nitrogen fixation genes in alphaproteobacteria. Based on the complete Rhizobium etli genome sequence, we constructed an R. etli CFN42 oligonucleotide (70-mer) microarray and utilized this tool, reverse transcription (RT)-PCR analysis (transcriptomics), proteomics, and bioinformatics to decipher the NifA-RpoN regulon under microaerobic conditions (free life) and in symbiosis with bean plants. The R. etli NifA-RpoN regulon was determined to contain 78 genes, including the genes involved in nitrogen fixation, and the analyses revealed 42 new NifA-RpoN-dependent genes. More importantly, this study demonstrated that the NifA-RpoN regulon is composed of genes and proteins that have very diverse functions, that play fundamental and previously less appreciated roles in regulating the normal physiology of the cell, and that have important functions in providing adequate conditions for efficient nitrogen fixation in symbiosis. The R. etli NifA-RpoN regulon defined here has some components in common with other NifA-RpoN regulons described previously, but the vast majority of the components have been found only in the R. etli regulon, suggesting that they have a specific role in this bacterium and particular requirements during nitrogen fixation compared with other symbiotic bacterial models.
authors.affiliation: Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Salazar
authors.forename: J Javier
authors.initials: JJ
authors.lastname: Díaz-Mejía
authors.forename: Gabriel
authors.initials: G
authors.lastname: Moreno-Hagelsieb
authors.forename: Gabriel
authors.initials: G
authors.lastname: Martínez-Batallar
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Mora
authors.forename: Jaime
authors.initials: J
authors.lastname: Mora
authors.forename: Sergio
authors.initials: S
authors.lastname: Encarnación
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019295:Computational Biology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D027805:Phaseolus / Q000382:microbiology*; D040901:Proteomics; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000378:metabolism; D018085:Regulon; D042163:Rhizobium etli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D013559:Symbiosis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C061338:NifA protein, Bacteria; D014157:Transcription Factors; D051877:RNA Polymerase Sigma 54
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