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J. Bacteriol., 11 1995, 6230-6236, Vol 177, No. 21
N Corbell and JE Loper
Mutations in the apdA (for antibiotic production) gene of the plant
root-colonizing bacterium Pseudomonas fluorescens Pf-5 pleiotropically
abolish the production of an array of antibiotics, including pyrrolnitrin,
pyoluteorin, and 2,4-diacetylphloroglucinol, as well as the production of
tryptophan side chain oxidase, hydrogen cyanide, and an extracellular
protease. The lack of production of secondary metabolites by ApdA- mutants
was correlated with the loss of inhibition of the phytopathogenic fungus
Rhizoctonia solani in culture. Sequencing of the apdA region identified an
open reading frame of 2,751 bp. The predicted amino acid sequence of the
apdA gene contains conserved domains of the histidine kinases that serve as
sensor components of prokaryotic two-component regulatory systems. The apdA
nucleotide and predicted amino acid sequences are strikingly similar to the
sequences of lemA and repA, genes encoding putative sensor kinases that are
required for the pathogenicity of Pseudomonas syringae pv. syringae and
Pseudomonas viridiflava, respectively. Introduction of the cloned apdA+
gene restored the wild-type phenotype to both LemA- mutants of P. syringae
and ApdA- mutants of Pf-5. The 101-kDa ApdA protein reacted with an
anti-LemA antiserum, further demonstrating the similarity of ApdA to LemA.
These results show that apdA encodes a putative sensor kinase component of
a classical two-component regulatory system that is required for
secondary-metabolite production by P. fluorescens Pf-5.
Copyright © 1995, American Society for Microbiology
A global regulator of secondary metabolite production in Pseudomonas fluorescens Pf-5
Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331, USA.
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