Inactivation of the GacA response regulator in Pseudomonas fluorescens Pf-5 has far-reaching transcriptomic consequences.
The GacS/GacA signal transduction system is a central regulator in Pseudomonas spp., including the biological control strain P. fluorescens Pf-5, in which GacS/GacA controls the production of secondary metabolites and exoenzymes that suppress plant pathogens. A whole genome oligonucleotide microarray was developed for Pf-5 and used to assess the global transcriptomic consequences of a gacA mutation in P. fluorescens Pf-5. In cultures at the transition from exponential to stationary growth phase, GacA significantly influenced transcript levels of 635 genes, representing more than 10% of the 6147 annotated genes in the Pf-5 genome. Transcripts of genes involved in the production of hydrogen cyanide, the antibiotic pyoluteorin and the extracellular protease AprA were at a low level in the gacA mutant, whereas those functioning in siderophore production and other aspects of iron homeostasis were significantly higher in the gacA mutant than in wild-type Pf-5. Notable effects of gacA inactivation were also observed in the transcription of genes encoding components of a type VI secretion system and cytochrome c oxidase subunits. Two novel gene clusters expressed under the control of gacA were identified from transcriptome analysis, and we propose global-regulator-based genome mining as an approach to decipher the secondary metabolome of Pseudomonas spp.
Hassan
Karl A
KA
Department of Chemistry and Biomolecular Sciences, Macquarie University, NSW, Australia.
Johnson
Aaron
A
Shaffer
Brenda T
BT
Ren
Qinghu
Q
Kidarsa
Teresa A
TA
Elbourne
Liam D H
LD
Hartney
Sierra
S
Duboy
Robert
R
Goebel
Neal C
NC
Zabriskie
T Mark
TM
Paulsen
Ian T
IT
Loper
Joyce E
JE
D001426:Bacterial Proteins / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D005810:Multigene Family; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D017384:Sequence Deletion
D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D012329:RNA, Bacterial