Dataset Information

Listeria monocytogenes regulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence.

ABSTRACT: Previous studies have shown that Listeria monocytogenes flagellar motility genes, including flaA, encoding flagellin, are transcriptionally down-regulated at 37 degrees C. For some L. monocytogenes strains, temperature-dependent motility gene expression is less stringent. By using flaA-lacZ transcriptional fusions, we identified regions upstream of the -35/-10 promoter elements that are necessary for temperature-dependent expression of flaA in L. monocytogenes strain EGDe. Whereas the sequence of the flaA promoter region was identical in L. monocytogenes strain 10403S, transcriptional activity was only partially down-regulated at 37 degrees C in 10403S. This finding suggested that a transacting regulatory protein with differential expression or activity in EGDe might be involved in temperature-dependent transcription of flaA. Indeed, a protein factor capable of specifically binding to the flaA promoter region was identified in cytoplasmic extracts of EGDe by using affinity purification and MS. Deletion of the factor-encoding gene (lmo0674) resulted in loss of temperature-dependent flaA expression and an increase in flaA promoter activity. Expression of other motility genes was also deregulated in the lmo0674 deletion. We have designated lmo0674 as mogR, indicating its role as a motility gene repressor. In tissue culture models, MogR repression of flaA during intracellular infection was independent of temperature and a deletion of mogR reduced the capacity for cell-to-cell spread. During in vivo infection, a deletion of mogR resulted in a 250-fold decrease in virulence. These studies indicate that regulation of flagellar motility gene expression and/or other genes controlled by MogR is required for full virulence of L. monocytogenes.

SUBMITTER: Grundling A

PROVIDER: S-EPMC514476 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Listeria monocytogenes regulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence.

Gründling Angelika A Burrack Laura S LS Bouwer H G Archie HG Higgins Darren E DE

Proceedings of the National Academy of Sciences of the United States of America 20040809 33

Previous studies have shown that Listeria monocytogenes flagellar motility genes, including flaA, encoding flagellin, are transcriptionally down-regulated at 37 degrees C. For some L. monocytogenes strains, temperature-dependent motility gene expression is less stringent. By using flaA-lacZ transcriptional fusions, we identified regions upstream of the -35/-10 promoter elements that are necessary for temperature-dependent expression of flaA in L. monocytogenes strain EGDe. Whereas the sequence o ...[more]

PMID: 15302931

Similar Datasets

Project description:Flagellar motility is considered an important virulence factor in different pathogenic bacteria. In Listeria monocytogenes the transcriptional repressor MogR regulates motility in a temperature-dependent manner, directly repressing flagellar- and chemotaxis genes. The only other bacteria known to carry a mogR homolog are members of the Bacillus cereus group, which includes motile species such as B. cereus and Bacillus thuringiensis as well as the non-motile species Bacillus anthracis, Bacillus mycoides and Bacillus pseudomycoides. Furthermore, the main motility locus in B. cereus group bacteria, carrying the genes for flagellar synthesis, appears to be more closely related to L. monocytogenes than to Bacillus subtilis, which belongs to a separate phylogenetic group of Bacilli and does not carry a mogR ortholog. Here, we show that in B. thuringiensis, MogR overexpression results in non-motile cells devoid of flagella. Global gene expression profiling showed that 110 genes were differentially regulated by MogR overexpression, including flagellar motility genes, but also genes associated with virulence, stress response and biofilm lifestyle. Accordingly, phenotypic assays showed that MogR also affects cytotoxicity and biofilm formation in B. thuringiensis. Overexpression of a MogR variant mutated in two amino acids within the putative DNA binding domain restored phenotypes to those of an empty vector control. In accordance, introduction of these mutations resulted in complete loss in MogR binding to its candidate flagellar locus target site in vitro. In contrast to L. monocytogenes, MogR appears to be regulated in a growth-phase dependent and temperature-independent manner in B. thuringiensis 407. Interestingly, mogR was found to be conserved also in non-motile B. cereus group species such as B. mycoides and B. pseudomycoides, which both carry major gene deletions in the flagellar motility locus and where in B. pseudomycoides mogR is the only gene retained. Furthermore, mogR is expressed in non-motile B. anthracis. Altogether this provides indications of an expanded set of functions for MogR in B. cereus group species, beyond motility regulation. In conclusion, MogR constitutes a novel B. thuringiensis pleiotropic transcriptional regulator, acting as a repressor of motility genes, and affecting the expression of a variety of additional genes involved in biofilm formation and virulence.

Project description:Facultative bacterial pathogens must adapt to multiple stimuli to persist in the environment or establish infection within a host. Temperature is often utilized as a signal to control expression of virulence genes necessary for infection or genes required for persistence in the environment. However, very little is known about the molecular mechanisms that allow bacteria to adapt and respond to temperature fluctuations. Listeria monocytogenes (Lm) is a food-borne, facultative intracellular pathogen that uses flagellar motility to survive in the extracellular environment and to enhance initial invasion of host cells during infection. Upon entering the host, Lm represses transcription of flagellar motility genes in response to mammalian physiological temperature (37°C) with a concomitant temperature-dependent up-regulation of virulence genes. We previously determined that down-regulation of flagellar motility is required for virulence and is governed by the reciprocal activities of the MogR transcriptional repressor and the bifunctional flagellar anti-repressor/glycosyltransferase, GmaR. In this study, we determined that GmaR is also a protein thermometer that controls temperature-dependent transcription of flagellar motility genes. Two-hybrid and gel mobility shift analyses indicated that the interaction between MogR and GmaR is temperature sensitive. Using circular dichroism and limited proteolysis, we determined that GmaR undergoes a temperature-dependent conformational change as temperature is elevated. Quantitative analysis of GmaR in Lm revealed that GmaR is degraded in the absence of MogR and at 37°C (when the MogR:GmaR complex is less stable). Since MogR represses transcription of all flagellar motility genes, including transcription of gmaR, changes in the stability of the MogR:GmaR anti-repression complex, due to conformational changes in GmaR, mediates repression or de-repression of flagellar motility genes in Lm. Thus, GmaR functions as a thermo-sensing anti-repressor that incorporates temperature signals into transcriptional control of flagellar motility. To our knowledge, this is the first example of a protein thermometer that functions as an anti-repressor to control a developmental process in bacteria.

Project description:While the stress-responsive alternative sigma factor sigma(B) has been identified in different species of Bacillus, Listeria, and Staphylococcus, the sigma(B) regulon has been extensively characterized only in B. subtilis. We combined biocomputing and microarray-based strategies to identify sigma(B)-dependent genes in the facultative intracellular pathogen Listeria monocytogenes. Hidden Markov model (HMM)-based searches identified 170 candidate sigma(B)-dependent promoter sequences in the strain EGD-e genome sequence. These data were used to develop a specialized, 208-gene microarray, which included 166 genes downstream of HMM-predicted sigma(B)-dependent promoters as well as selected virulence and stress response genes. RNA for the microarray experiments was isolated from both wild-type and Delta sigB null mutant L. monocytogenes cells grown to stationary phase or exposed to osmotic stress (0.5 M KCl). Microarray analyses identified a total of 55 genes with statistically significant sigma(B)-dependent expression under the conditions used in these experiments, with at least 1.5-fold-higher expression in the wild type over the sigB mutant under either stress condition (51 genes showed at least 2.0-fold-higher expression in the wild type). Of the 55 genes exhibiting sigma(B)-dependent expression, 54 were preceded by a sequence resembling the sigma(B) promoter consensus sequence. Rapid amplification of cDNA ends-PCR was used to confirm the sigma(B)-dependent nature of a subset of eight selected promoter regions. Notably, the sigma(B)-dependent L. monocytogenes genes identified through this HMM/microarray strategy included both stress response genes (e.g., gadB, ctc, and the glutathione reductase gene lmo1433) and virulence genes (e.g., inlA, inlB, and bsh). Our data demonstrate that, in addition to regulating expression of genes important for survival under environmental stress conditions, sigma(B) also contributes to regulation of virulence gene expression in L. monocytogenes. These findings strongly suggest that sigma(B) contributes to L. monocytogenes gene expression during infection.

Project description:UnlabelledIn this study, we sought to characterize the targets of the abundant Listeria monocytogenes noncoding RNA Rli31, which is required for L. monocytogenes lysozyme resistance and pathogenesis. Whole-genome sequencing of lysozyme-resistant suppressor strains identified loss-of-expression mutations in the promoter of spoVG, and deletion of spoVG rescued lysozyme sensitivity and attenuation in vivo of the rli31 mutant. SpoVG was demonstrated to be an RNA-binding protein that interacted with Rli31 in vitro. The relationship between Rli31 and SpoVG is multifaceted, as both the spoVG-encoded protein and the spoVG 5′-untranslated region interacted with Rli31. In addition, we observed that spoVG-deficient bacteria were nonmotile in soft agar and suppressor mutations that restored swarming motility were identified in the gene encoding a major RNase in Gram-positive bacteria, RNase J1. Collectively, these findings suggest that SpoVG is similar to global posttranscriptional regulators, a class of RNA-binding proteins that interact with noncoding RNA, regulate genes in concert with RNases, and control pleiotropic aspects of bacterial physiology.ImportancespoVG is widely conserved among bacteria; however, the function of this gene has remained unclear since its initial characterization in 1977. Mutation of spoVG impacts various phenotypes in Gram-positive bacteria, including methicillin resistance, capsule formation, and enzyme secretion in Staphylococcus aureus and also asymmetric cell division, hemolysin production, and sporulation in Bacillus subtilis. Here, we demonstrate that spoVG mutant strains of Listeria monocytogenes are hyper-lysozyme resistant, hypervirulent, nonmotile, and misregulate genes controlling carbon metabolism. Furthermore, we demonstrate that SpoVG is an RNA-binding protein. These findings suggest that SpoVG has a role in L. monocytogenes, and perhaps in other bacteria, as a global gene regulator. Posttranscriptional gene regulators help bacteria adapt to various environments and coordinate differing aspects of bacterial physiology. SpoVG may help the organism coordinate environmental growth and virulence to survive as a facultative pathogen.

Dataset Information

Listeria monocytogenes regulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence.

Publications

Listeria monocytogenes regulates flagellar motility gene expression through MogR, a transcriptional repressor required for virulence.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets