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Gene Review

rpoN  -  RNA polymerase factor sigma-54

Pseudomonas aeruginosa PAO1

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Disease relevance of rpoN

  • rpoN Gene of Pseudomonas aeruginosa Alters Its Susceptibility to Quinolones and Carbapenems [1].
  • The product of the rpoN gene is an alternative sigma factor of RNA polymerase which is required for transcription of a number of genes in members of the family Enterobacteriaceae, including those that specify enzymes of nitrogen assimilation, amino acid uptake, and degradation of a variety of organic molecules [2].

High impact information on rpoN

  • In addition, expression of the flagellum is coordinately regulated with other P. aeruginosa virulence factors by the alternative sigma factor sigma54, encoded by rpoN [3].
  • The role of PilA in the GSP was examined, using P. aeruginosa mutants in the pilA gene, or in rpoN, a gene regulating pilA expression [4].
  • Mutagenesis studies have indicated that P. aeruginosa adhesion is under the control of the rpoN gene, which also regulates pilin synthesis, flagellum formation, and other functions [5].
  • Mutagenesis of certain flagellar genes that are not controlled by RpoN, e.g., flif, also indicates a close relationship between adhesion and flagellar genes and not necessarily an independent effect of rpoN on adhesion [5].
  • Quantitative real-time PCR revealed that stationary-phase cells of the rpoN mutant grown without an antimicrobial agent had approximately 4- to 140- and 2- to 14-fold-higher levels of transcripts of the pvdS and vqsR genes, respectively, than the wild-type strain [1].

Biological context of rpoN

  • By contrast, in an rpoN mutant, the expression of the gacA global regulatory gene was significantly increased during the entire growth cycle, whereas another global regulatory gene, vfr, was downregulated at high cell densities [6].
  • In contrast, specific antibody was capable of causing similar enhancement of bacterial uptake regardless of the rpoN phenotype [7].
  • These findings suggest that rpoN is involved in tolerance to antimicrobial agents in P. aeruginosa and that its tolerant effect is partly dependent on increased pyoverdine production and vqsR gene expression [1].
  • Partial complementation of motility in nonmotile P. aeruginosa isolates was achieved by introduction of extra copies of the rpoN locus carried on plasmid pPT212, indicating that the alternate sigma factor, RpoN, may be involved in the coordinate regulation of virulence factors during CF infection [8].

Anatomical context of rpoN

  • The rpoN mutation had a minimal effect on the interaction of bacteria with erythrocytes, indicating that the transcription of a gene(s) specifying the agglutination phenomenon does not utilize rpoN [9].

Associations of rpoN with chemical compounds

  • In order to characterize these mucin-binding adhesins, outer membrane proteins (OMP) from two adhesive strains, 1244-NP and PAK-NP, and their poorly adhesive rpoN mutants, 1244-N3 and PAK-N1, were prepared by a mild extraction with Zwittergent 3-14 [10].
  • PA14 rpoN::Gen(r) synthesized reduced levels of pyocyanin and displayed a variety of phenotypes typical of rpoN mutants, including a lack of motility and the failure to grow on nitrate, glutamate, or histidine as the sole nitrogen source [11].
  • However, the rpoN mutants were glutamine auxotrophs and were defective in glutamine synthetase, indicating defects in nitrogen assimilation [2].

Other interactions of rpoN

  • The fhp promoter was inactive in the fhpR or rpoN mutant strain, suggesting that the NO-sensing regulation of the fhp promoter was mediated by FhpR [12].
  • P. aeruginosa mutants pilA and fliF, but not rpoN, colonized normal respiratory xenografts, indicating that colonization and infection in this model depend on an uncharacterized RpoN-controlled gene [13].
  • Transcription from the algC promoter, which has significant homology with the RNA polymerase sigma-54 (RpoN) recognition sequence, decreased in an rpoN mutant of P. aeruginosa [14].
  • AlgT-dependent control of flagellum synthesis occurred through inhibition of fliC but not rpoN transcription [15].
  • Insertional inactivation of rpoN (ntrA) in PAO568 did not affect algR and algD transcription [16].

Analytical, diagnostic and therapeutic context of rpoN

  • Flow cytometry assays using a green fluorescent protein reporter demonstrated increased expression of the vqsR gene in the rpoN mutant throughout growth [1].


  1. rpoN Gene of Pseudomonas aeruginosa Alters Its Susceptibility to Quinolones and Carbapenems. Viducic, D., Ono, T., Murakami, K., Katakami, M., Susilowati, H., Miyake, Y. Antimicrob. Agents Chemother. (2007) [Pubmed]
  2. The rpoN gene product of Pseudomonas aeruginosa is required for expression of diverse genes, including the flagellin gene. Totten, P.A., Lara, J.C., Lory, S. J. Bacteriol. (1990) [Pubmed]
  3. A four-tiered transcriptional regulatory circuit controls flagellar biogenesis in Pseudomonas aeruginosa. Dasgupta, N., Wolfgang, M.C., Goodman, A.L., Arora, S.K., Jyot, J., Lory, S., Ramphal, R. Mol. Microbiol. (2003) [Pubmed]
  4. Interactions of the components of the general secretion pathway: role of Pseudomonas aeruginosa type IV pilin subunits in complex formation and extracellular protein secretion. Lu, H.M., Motley, S.T., Lory, S. Mol. Microbiol. (1997) [Pubmed]
  5. Recognition of mucin by the adhesin-flagellar system of Pseudomonas aeruginosa. Ramphal, R., Arora, S.K., Ritchings, B.W. Am. J. Respir. Crit. Care Med. (1996) [Pubmed]
  6. Negative control of quorum sensing by RpoN (sigma54) in Pseudomonas aeruginosa PAO1. Heurlier, K., Dénervaud, V., Pessi, G., Reimmann, C., Haas, D. J. Bacteriol. (2003) [Pubmed]
  7. Mechanisms of nonopsonic phagocytosis of Pseudomonas aeruginosa. Mork, T., Hancock, R.E. Infect. Immun. (1993) [Pubmed]
  8. Nonmotility and phagocytic resistance of Pseudomonas aeruginosa isolates from chronically colonized patients with cystic fibrosis. Mahenthiralingam, E., Campbell, M.E., Speert, D.P. Infect. Immun. (1994) [Pubmed]
  9. Adhesion of Pseudomonas aeruginosa pilin-deficient mutants to mucin. Ramphal, R., Koo, L., Ishimoto, K.S., Totten, P.A., Lara, J.C., Lory, S. Infect. Immun. (1991) [Pubmed]
  10. Pseudomonas aeruginosa outer membrane adhesins for human respiratory mucus glycoproteins. Carnoy, C., Scharfman, A., Van Brussel, E., Lamblin, G., Ramphal, R., Roussel, P. Infect. Immun. (1994) [Pubmed]
  11. Differential roles of the Pseudomonas aeruginosa PA14 rpoN gene in pathogenicity in plants, nematodes, insects, and mice. Hendrickson, E.L., Plotnikova, J., Mahajan-Miklos, S., Rahme, L.G., Ausubel, F.M. J. Bacteriol. (2001) [Pubmed]
  12. Transcriptional regulation of the flavohemoglobin gene for aerobic nitric oxide detoxification by the second nitric oxide-responsive regulator of Pseudomonas aeruginosa. Arai, H., Hayashi, M., Kuroi, A., Ishii, M., Igarashi, Y. J. Bacteriol. (2005) [Pubmed]
  13. Pseudomonas aeruginosa infection of respiratory epithelium in a cystic fibrosis xenograft model. Cohn, L.A., Weber, A., Phillips, T., Lory, S., Kaplan, M., Smith, A. J. Infect. Dis. (2001) [Pubmed]
  14. Alginate synthesis in Pseudomonas aeruginosa: environmental regulation of the algC promoter. Zielinski, N.A., Maharaj, R., Roychoudhury, S., Danganan, C.E., Hendrickson, W., Chakrabarty, A.M. J. Bacteriol. (1992) [Pubmed]
  15. Negative control of flagellum synthesis in Pseudomonas aeruginosa is modulated by the alternative sigma factor AlgT (AlgU). Garrett, E.S., Perlegas, D., Wozniak, D.J. J. Bacteriol. (1999) [Pubmed]
  16. Role of the far-upstream sites of the algD promoter and the algR and rpoN genes in environmental modulation of mucoidy in Pseudomonas aeruginosa. Mohr, C.D., Martin, D.W., Konyecsni, W.M., Govan, J.R., Lory, S., Deretic, V. J. Bacteriol. (1990) [Pubmed]
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