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The extracytoplasmic function sigma factor ?VreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa.

ABSTRACT: The extracytoplasmic function sigma factor ?VreI of the human pathogen Pseudomonas aeruginosa promotes transcription of potential virulence determinants, including secretion systems and secreted proteins. Its activity is modulated by the VreR anti-? factor that inhibits the binding of ?VreI to the RNA polymerase in the absence of a (still unknown) inducing signal. The vreI-vreR genes are expressed under inorganic phosphate (Pi) starvation, a physiological condition often encountered in the host that increases P. aeruginosa pathogenicity. However, whether or not ?VreI is active in vivo during infection and contributes to the Pi starvation-induced virulence of this pathogen has not been analyzed yet. Using zebrafish embryos and a human alveolar basal epithelial cell line as P. aeruginosa hosts, we demonstrate in this work that ?VreI is active during infection and that lack of ?VreI considerably reduces the Pi starvation-induced virulence of this pathogen. Surprisingly, lack of the ?VreI inhibitor, the VreR anti-? factor, also diminishes the virulence of P. aeruginosa. By transcriptomic analyses we show that VreR modulates gene expression not only in a ?VreI-dependent but also in a ?VreI-independent manner. This includes potential virulence determinants and transcriptional regulators that could be responsible for the reduced virulence of the ?vreR mutant.

SUBMITTER: Otero-Asman JR

PROVIDER: S-EPMC7035377 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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The extracytoplasmic function sigma factor σVreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa.

Otero-Asman Joaquín R JR Quesada José M JM Jim Kin K KK Ocampo-Sosa Alain A Civantos Cristina C Bitter Wilbert W Llamas María A MA

Scientific reports 20200221 1

The extracytoplasmic function sigma factor σVreI of the human pathogen Pseudomonas aeruginosa promotes transcription of potential virulence determinants, including secretion systems and secreted proteins. Its activity is modulated by the VreR anti-σ factor that inhibits the binding of σVreI to the RNA polymerase in the absence of a (still unknown) inducing signal. The vreI-vreR genes are expressed under inorganic phosphate (Pi) starvation, a physiological condition often en ...[more]

PMID: 32081993

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Project description:In Pseudomonas aeruginosa, iron modulates gene expression through a cascade of negative and positive regulatory proteins. The master regulator Fur is involved in iron-dependent repression of several genes. One of these genes, pvdS, was predicted to encode a putative sigma factor responsible for the transcription of a subset of genes of the Fur regulon. PvdS appears to belong to a structurally and functionally distinct subgroup of the extracytoplasmic function family of alternative sigma factors. Members of this subgroup, also including PbrA from Pseudomonas fluorescens, PfrI and PupI from Pseudomonas putida, and FecI from Escherichia coli, are controlled by the Fur repressor, and they activate transcription of genes for the biosynthesis or the uptake of siderophores. Evidence is provided that the PvdS protein of P. aeruginosa is endowed with biochemical properties of eubacterial sigma factors, as it spontaneously forms 1:1 complexes with the core fraction of RNA polymerase (RNAP, alpha(2)betabeta' subunits), thereby promoting in vitro binding of the PvdS-RNAP holoenzyme to the promoter region of the pvdA gene. These functional features of PvdS are consistent with the presence of structural domains predicted to be involved in core RNAP binding, promoter recognition, and open complex formation. The activity of pyoverdin biosynthetic (pvd) promoters was significantly lower in E. coli overexpressing the multicopy pvdS gene than in wild-type P. aeruginosa PAO1 carrying the single gene copy, and pvd::lacZ transcriptional fusions were silent in both pfrI (the pvdS homologue) and pfrA (a positive regulator of pseudobactin biosynthetic genes) mutants of P. putida WCS358, while they are expressed at PAO1 levels in wild-type WCS358. Moreover, the PvdS-RNAP holoenzyme purified from E. coli lacked the ability to generate in vitro transcripts from the pvdA promoter. These observations suggest that at least one additional positive regulator could be required for full activity of the PvdS-dependent transcription complex both in vivo and in vitro. This is consistent with the presence of a putative activator binding site (the iron starvation box) at variable distance from the transcription initiation sites of promoters controlled by the iron starvation sigma factors PvdS, PfrI, and PbrA of fluorescent pseudomonads.

Dataset Information

The extracytoplasmic function sigma factor ?VreI is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa.

Publications

The extracytoplasmic function sigma factor σ<sup>VreI</sup> is active during infection and contributes to phosphate starvation-induced virulence of Pseudomonas aeruginosa.

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