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Gene Review

gacA  -  response regulator GacA

Pseudomonas protegens Pf-5

 
 
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Disease relevance of gacA

  • The gacA-uvrC cluster is homologous to the orf-2 (= uvrY)-uvrC operon of Escherichia coli [1].
  • The varA locus is a homolog of gacA (originally described for the soil organism Pseudomonas fluorescens), which encodes a conserved global regulator belonging to the family of two-component signal transducing molecules [2].
 

High impact information on gacA

  • In the biocontrol strain CHA0 of Pseudomonas fluorescens, the response regulator GacA is essential for the synthesis of extracellular protease (AprA) and secondary metabolites including hydrogen cyanide [3].
  • We discovered that mutations in a P. fluorescens gene named gacA (for global antibiotic and cyanide control) pleiotropically block the production of the secondary metabolites 2,4-diacetylphloroglucinol (Phl), HCN, and pyoluteorin [1].
  • The gacA mutants of strain CHA0 have a drastically reduced ability to suppress black root rot under gnotobiotic conditions, supporting the previous observations that the antibiotic Phl and HCN individually contribute to the suppression of black root rot [1].
  • Transcription of rsmY was enhanced by the addition of the strain's own supernatant extract containing a quorum-sensing signal and was abolished in gacS or gacA mutants [4].
  • A genetic map was derived from the physical map by southern hybridization and 31 genes were positioned including oriC, rDNA operons (rnnA-E), recA, gacA, and pyvD [5].
 

Chemical compound and disease context of gacA

  • Effect of transferring 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase genes into Pseudomonas fluorescens strain CHA0 and its gacA derivative CHA96 on their growth-promoting and disease-suppressive capacities [6].
  • The gacA gene of the biocontrol strain Pseudomonas fluorescens CHA0 codes for a response regulator which, together with the sensor kinase GacS (=LemA), is required for the production of exoenzymes and secondary metabolites involved in biocontrol, including hydrogen cyanide (HCN) [7].
 

Biological context of gacA

  • Mutations in gacS and gacA compromised the capacity of stationary-phase cells of Pf-5 to survive exposure to oxidative stress [8].
  • Culture supernatants of strain CHA0 inhibited egg hatching and induced mortality of M. incognita juveniles more strongly than did supernatants of aprA and gacA mutants, suggesting that AprA protease contributes to biocontrol [9].
  • Variant F showed alterations in traits that have been shown to be important for rhizosphere colonization, such as siderophore, cyanide, and exoprotease production, and these phenotypes were complemented by a cloned gacA [10].
  • Northern analysis indicated that the locus encodes an RNA (PrrB RNA) which is able to phenotypically complement gacS and gacA mutants and is itself regulated by the GacS-GacA two-component signal transduction system [11].
  • In Pseudomonasfluorescens strain CHAO, the response regulator gene gacA controls expression of extracellular enzymes and antifungal secondary metabolites, which are important for this strain's biocontrol activity in the plant rhizosphere [12].
 

Associations of gacA with chemical compounds

 

Other interactions of gacA

  • At the entrance to stationary phase, sigmaS content in gacS and gacA mutants of Pf-5 was less than 20% of the wild-type level [8].
  • Overexpression of rsmZ effectively suppressed the negative effect of gacS and gacA mutations on target genes, i.e., hcnA (for hydrogen cyanide synthase) and aprA (for the major exoprotease) [13].
  • Multicopy suppression of a gacA mutation by the infC operon in Pseudomonas fluorescens CHA0: competition with the global translational regulator RsmA [7].
  • Extracellular protease and phospholipase C are controlled by the global regulatory gene gacA in the biocontrol strain Pseudomonas fluorescens CHA0 [14].
  • In contrast, the production of another exoenzyme, lipase, is not regulated by the gacA gene [14].
 

Analytical, diagnostic and therapeutic context of gacA

References

  1. Global control in Pseudomonas fluorescens mediating antibiotic synthesis and suppression of black root rot of tobacco. Laville, J., Voisard, C., Keel, C., Maurhofer, M., Défago, G., Haas, D. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  2. Modulation of expression of the ToxR regulon in Vibrio cholerae by a member of the two-component family of response regulators. Wong, S.M., Carroll, P.A., Rahme, L.G., Ausubel, F.M., Calderwood, S.B. Infect. Immun. (1998) [Pubmed]
  3. Global GacA-steered control of cyanide and exoprotease production in Pseudomonas fluorescens involves specific ribosome binding sites. Blumer, C., Heeb, S., Pessi, G., Haas, D. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  4. RsmY, a small regulatory RNA, is required in concert with RsmZ for GacA-dependent expression of biocontrol traits in Pseudomonas fluorescens CHA0. Valverde, C., Heeb, S., Keel, C., Haas, D. Mol. Microbiol. (2003) [Pubmed]
  5. Physical and genetic map of the Pseudomonas fluorescens SBW25 chromosome. Rainey, P.B., Bailey, M.J. Mol. Microbiol. (1996) [Pubmed]
  6. Effect of transferring 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase genes into Pseudomonas fluorescens strain CHA0 and its gacA derivative CHA96 on their growth-promoting and disease-suppressive capacities. Wang, C., Knill, E., Glick, B.R., Défago, G. Can. J. Microbiol. (2000) [Pubmed]
  7. Multicopy suppression of a gacA mutation by the infC operon in Pseudomonas fluorescens CHA0: competition with the global translational regulator RsmA. Blumer, C., Haas, D. FEMS Microbiol. Lett. (2000) [Pubmed]
  8. The two-component regulators GacS and GacA influence accumulation of the stationary-phase sigma factor sigmaS and the stress response in Pseudomonas fluorescens Pf-5. Whistler, C.A., Corbell, N.A., Sarniguet, A., Ream, W., Loper, J.E. J. Bacteriol. (1998) [Pubmed]
  9. Extracellular protease of Pseudomonas fluorescens CHA0, a biocontrol factor with activity against the root-knot nematode Meloidogyne incognita. Siddiqui, I.A., Haas, D., Heeb, S. Appl. Environ. Microbiol. (2005) [Pubmed]
  10. Phenotypic selection and phase variation occur during alfalfa root colonization by Pseudomonas fluorescens F113. Sánchez-Contreras, M., Martín, M., Villacieros, M., O'Gara, F., Bonilla, I., Rivilla, R. J. Bacteriol. (2002) [Pubmed]
  11. A regulatory RNA (PrrB RNA) modulates expression of secondary metabolite genes in Pseudomonas fluorescens F113. Aarons, S., Abbas, A., Adams, C., Fenton, A., O'Gara, F. J. Bacteriol. (2000) [Pubmed]
  12. Characterization of spontaneous gacS and gacA regulatory mutants of Pseudomonas fluorescens biocontrol strain CHAO. Bull, C.T., Duffy, B., Voisard, C., Défago, G., Keel, C., Haas, D. Antonie Van Leeuwenhoek (2001) [Pubmed]
  13. Regulatory RNA as mediator in GacA/RsmA-dependent global control of exoproduct formation in Pseudomonas fluorescens CHA0. Heeb, S., Blumer, C., Haas, D. J. Bacteriol. (2002) [Pubmed]
  14. Extracellular protease and phospholipase C are controlled by the global regulatory gene gacA in the biocontrol strain Pseudomonas fluorescens CHA0. Sacherer, P., Défago, G., Haas, D. FEMS Microbiol. Lett. (1994) [Pubmed]
 
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