Global GacA-steered control of cyanide and exoprotease production in Pseudomonas fluorescens involves specific ribosome binding sites.
The conserved two-component regulatory system GacS/GacA determines the expression of extracellular products and virulence factors in a variety of Gram-negative bacteria. 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. GacA was found to exert its control on the hydrogen cyanide biosynthetic genes (hcnABC) and on the aprA gene indirectly via a posttranscriptional mechanism. Expression of a translational hcnA'-'lacZ fusion was GacA-dependent whereas a transcriptional hcnA-lacZ fusion was not. A distinct recognition site overlapping with the ribosome binding site appears to be primordial for GacA-steered regulation. GacA-dependence could be conferred to the Escherichia coli lacZ mRNA by a 3-bp substitution in the ribosome binding site. The gene coding for the global translational repressor RsmA of P. fluorescens was cloned. RsmA overexpression mimicked partial loss of GacA function and involved the same recognition site, suggesting that RsmA is a downstream regulatory element of the GacA control cascade. Mutational inactivation of the chromosomal rsmA gene partially suppressed a gacS defect. Thus, a central, GacA-dependent switch from primary to secondary metabolism may operate at the level of translation.
Blumer
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Laboratoire de Biologie Microbienne, Université de Lausanne, CH-1015 Lausanne, Switzerland.
Heeb
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S
Pessi
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Haas
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D
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D003001:Cloning, Molecular; D003486:Cyanides / Q000378:metabolism; D010450:Endopeptidases / Q000096:biosynthesis* / Q000235:genetics; D020689:Exopeptidases / Q000096:biosynthesis; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000096:biosynthesis* / Q000235:genetics; D016296:Mutagenesis; D009876:Operon; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; D014176:Protein Biosynthesis; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014774:Virulence
D001426:Bacterial Proteins; D003486:Cyanides; C091100:GacA protein, Bacteria; D009097:Multienzyme Complexes; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C095468:RsmA protein, Erwinia carotovora; D014157:Transcription Factors; D010088:Oxidoreductases; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; C112800:glycine dehydrogenase (cyanide-forming); C074165:lemA protein, bacterial; D010450:Endopeptidases; D020689:Exopeptidases; C087822:alkaline protease