The ssgB gene, encoding a member of the regulon of stress-response sigma factor ?H, is essential for aerial mycelium septation in Streptomyces coelicolor A3(2)

ABSTRACT Sporulation mutants of Streptomyces coelicolor appear white because they are defective in the synthesis of the gray polyketide spore pigment, and such white (whi) mutants have been used to define 13 sporulation loci. whiN, one of five new whi loci identified in a recent screen of NTG (N-methyl-N′-nitro-N-nitrosoguanidine)-inducedwhi strains (N. J. Ryding et al., J. Bacteriol. 181:5419–5425, 1999), was defined by two mutants, R112 and R650. R650 produced frequent spores that were longer than those of the wild type. In contrast, R112 produced long, straight, undifferentiated hyphae, although rare spore chains were observed, sometimes showing highly irregular septum placement. Subcloning and sequencing showed thatwhiN encodes a member of the extracytoplasmic function subfamily of RNA polymerase sigma factors and that the sigma factor has an unusual N-terminal extension of approximately 86 residues that is not present in other sigma factors. A constructed whiN null mutant failed to form aerial mycelium (the “bald” phenotype) and, as a consequence, whiN was renamed bldN. This observation was not totally unexpected because, on some media, the R112 point mutant produced substantially less aerial mycelium than its parent, M145. The bldN null mutant did not fit simply into the extracellular signaling cascade proposed for S. coelicolor bld mutants. Expression of bldN was analyzed during colony development in wild-type and aerial mycelium-deficientbld strains. bldN was transcribed from a single promoter, bldNp. bldN transcription was developmentally regulated, commencing approximately at the time of aerial mycelium formation, and depended on bldG and bldH, but not on bldA, bldB, bldC,bldF, bldK, or bldJ or onbldN itself. Transcription from the p1 promoter of the response-regulator gene bldM depended onbldN in vivo, and the bldMp1 promoter was shown to be a direct biochemical target for ςBldN holoenzyme in vitro.

Download Full-text

Cascade of sigma factors in streptomycetes: identification of a new extracytoplasmic function sigma factor σJ that is under the control of the stress-response sigma factor σH in Streptomyces coelicolor A3(2)

Archives of Microbiology ◽

10.1007/s00203-006-0158-9 ◽

2006 ◽

Vol 186 (6) ◽

pp. 435-446 ◽

Cited By ~ 8

Author(s):

Vladislava Mazurakova ◽

Beatrica Sevcikova ◽

Bronislava Rezuchova ◽

Jan Kormanec

Keyword(s):

Stress Response ◽

Sigma Factor ◽

Streptomyces Coelicolor ◽

Sigma Factors ◽

Extracytoplasmic Function Sigma Factor

Download Full-text

The RpoH-Mediated Stress Response in Neisseria gonorrhoeae Is Regulated at the Level of Activity

Journal of Bacteriology ◽

10.1128/jb.186.24.8443-8452.2004 ◽

2004 ◽

Vol 186 (24) ◽

pp. 8443-8452 ◽

Cited By ~ 19

Author(s):

Lina Laskos ◽

Catherine S. Ryan ◽

Janet A. M. Fyfe ◽

John K. Davies

Keyword(s):

Stress Response ◽

Neisseria Gonorrhoeae ◽

Molecular Chaperones ◽

Sigma Factor ◽

Mutational Analysis ◽

Normal Growth ◽

Gene Encoding ◽

General Stress Response ◽

Level Of Activity ◽

Genes Encoding

ABSTRACT The general stress response in Neisseria gonorrhoeae was investigated. Transcriptional analyses of the genes encoding the molecular chaperones DnaK, DnaJ, and GrpE suggested that they are transcribed from σ32 (RpoH)-dependent promoters upon exposure to stress. This was confirmed by mutational analysis of the σ32 promoter of dnaK. The gene encoding the gonococcal RpoH sigma factor appears to be essential, as we could not isolate viable mutants. Deletion of an unusually long rpoH leader sequence resulted in elevated levels of transcription, suggesting that this region is involved in negative regulation of RpoH expression during normal growth. Transcriptional analyses and protein studies determined that regulation of the RpoH-mediated stress response is different from that observed in most other species, in which regulation occurs predominantly at the transcriptional and translational levels. We suggest that an increase in the activity of preformed RpoH is primarily responsible for induction of the stress response in N. gonorrhoeae.

Download Full-text

Secreted-Protein Response to σU Activity in Streptomyces coelicolor

Journal of Bacteriology ◽

10.1128/jb.01759-07 ◽

2007 ◽

Vol 190 (3) ◽

pp. 894-904 ◽

Cited By ~ 19

Author(s):

Nadria D. Gordon ◽

Geri L. Ottaviano ◽

Sarah E. Connell ◽

Gregory V. Tobkin ◽

Crystal H. Son ◽

...

Keyword(s):

Sigma Factor ◽

Fluorescent Protein ◽

Cell Envelope ◽

Streptomyces Coelicolor ◽

Morphological Differentiation ◽

Aerial Mycelium ◽

Secreted Proteins ◽

Wild Type ◽

Extracellular Proteome ◽

Peptide Mass

ABSTRACT The filamentous bacterium Streptomyces coelicolor forms an aerial mycelium as a prerequisite to sporulation, which occurs in the aerial hyphae. Uncontrolled activity of the extracytoplasmic function sigma factor σU blocks the process of aerial mycelium formation in this organism. Using a green fluorescent protein transcriptional reporter, we have demonstrated that sigU transcription is autoregulated. We have defined a σU-dependent promoter sequence and used this to identify 22 likely σU regulon members in the S. coelicolor genome. Since many of these genes encode probable secreted proteins, we characterized the extracellular proteome of a mutant with high σU activity caused by disruption of rsuA, the presumed cognate anti-sigma factor of σU. This mutant secreted a much greater quantity and diversity of proteins than the wild-type strain. Peptide mass fingerprinting was used to identify 79 proteins from the rsuA mutant culture supernatant. The most abundant species, SCO2217, SCO0930, and SCO2207, corresponded to secreted proteins or lipoproteins of unknown functions whose genes are in the proposed σU regulon. Several unique proteases were also detected in the extracellular proteome of the mutant, and the levels of the protease inhibitor SCO0762 were much reduced compared to those of the wild type. Consequently, extracellular protease activity was elevated about fourfold in the rsuA mutant. The functions of the proteins secreted as a result of σU activity may be important for combating cell envelope stress and modulating morphological differentiation in S. coelicolor.

Download Full-text

The Anti-Anti-Sigma Factor BldG Is Involved in Activation of the Stress Response Sigma Factor σH in Streptomyces coelicolor A3(2)

Journal of Bacteriology ◽

10.1128/jb.00828-10 ◽

2010 ◽

Vol 192 (21) ◽

pp. 5674-5681 ◽

Cited By ~ 19

Author(s):

Beatrica Sevcikova ◽

Bronislava Rezuchova ◽

Dagmar Homerova ◽

Jan Kormanec

Keyword(s):

Stress Response ◽

Osmotic Stress ◽

Sigma Factor ◽

Streptomyces Coelicolor ◽

Direct Interaction ◽

Morphological Differentiation ◽

Osmotic Stress Response ◽

Its Gene ◽

Two Hybrid

ABSTRACT The alternative stress response sigma factor σH has a role in regulation of the osmotic stress response and in morphological differentiation in Streptomyces coelicolor A3(2). Its gene, sigH, is located in an operon with the gene that encodes its anti-sigma factor UshX (PrsH). However, no gene with similarity to an anti-anti-sigma factor which may have a role in σH activation by a “partner-switching” mechanism is located in the operon. By using a combination of several approaches, including pull-down and bacterial two-hybrid assays and visualization of the complex by native polyacrylamide electrophoresis, we demonstrated a direct interaction between UshX and the pleiotropic sporulation-specific anti-anti-sigma factor BldG. Osmotic induction of transcription of the sigHp2 promoter that is specifically recognized by RNA polymerase containing σH was absent in an S. coelicolor bldG mutant, indicating a role of BldG in σH activation by a partner-switching-like mechanism.

Download Full-text

Ensifer aridi LMR001T Symbiosis and Tolerance to Stress Do Not Require the Alternative Sigma Factor RpoE2

Agronomy ◽

10.3390/agronomy11091787 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1787

Author(s):

Meryem Belfquih ◽

Ilham Sakrouhi ◽

Hassan Ait-Benhassou ◽

Emeric Dubois ◽

Dany Severac ◽

...

Keyword(s):

Stress Response ◽

Sigma Factor ◽

A Priori ◽

Climatic Conditions ◽

Targeted Mutagenesis ◽

Alternative Sigma Factor ◽

Gene Encoding ◽

General Stress Response ◽

Stress Genes ◽

General Stress

The recently proposed species Ensifer aridi represents an interesting model to study adaptive mechanisms explaining its maintenance under stressful pedo-climatic conditions. To get insights into functions associated with hyperosmotic stress adaptation in E. aridi, we first performed RNAseq profiling of cells grown under sub-lethal stresses applied by permeating (NaCl) and non-permeating (PEG8000) solutes that were compared to a transcriptome from unstressed bacteria. Then an a priori approach, consisting of targeted mutagenesis of the gene encoding alternative sigma factor (rpoE2), involved in the General Stress Response combined with phenotyping and promoter gfp fusion-based reporter assays of selected genes was carried out to examine the involvement of rpoE2 in symbiosis and stress response. The majority of motility and chemotaxis genes were repressed by both stresses. Results also suggest accumulation of compatible solute trehalose under stress and other metabolisms such as inositol catabolism or the methionine cycling-generating S-adenosyl methionine appears strongly induced notably under salt stress. Interestingly, many functions regulated by salt were shown to favor competitiveness for nodulation in other rhizobia, supporting a role of stress genes for proper symbiosis’ development and functioning. However, despite activation of the general stress response and identification of several genes possibly under its control, our data suggest that rpoE2 was not essential for stress tolerance and symbiosis’ development, indicating that E. aridi possesses alternative regulatory mechanisms to adapt and respond to stressful environments.

Download Full-text

RNA Polymerase Sigma Factor That Blocks Morphological Differentiation by Streptomyces coelicolor

Journal of Bacteriology ◽

10.1128/jb.183.20.5991-5996.2001 ◽

2001 ◽

Vol 183 (20) ◽

pp. 5991-5996 ◽

Cited By ~ 35

Author(s):

Amy M. Gehring ◽

Narie J. Yoo ◽

Richard Losick

Keyword(s):

Rna Polymerase ◽

Sigma Factor ◽

Insertional Mutagenesis ◽

Early Stage ◽

Streptomyces Coelicolor ◽

Morphological Differentiation ◽

Aerial Mycelium ◽

Growth Defect ◽

Insertion Mutant

ABSTRACT The filamentous bacterium Streptomyces coelicolorundergoes a complicated process of morphological differentiation that begins with the formation of an aerial mycelium and culminates in sporulation. Genes required for the initiation of aerial mycelium formation have been termed bld (bald), describing the smooth, undifferentiated colonies of mutant strains. By using an insertional mutagenesis protocol that relies on in vitro transposition, we have isolated a bld mutant harboring an insertion in a previously uncharacterized gene, SCE59.12c, renamed here rsuA. The insertion mutant exhibited no measurable growth defect but failed to produce an aerial mycelium and showed a significant delay in the production of the polyketide antibiotic actinorhodin. The rsuA gene encodes an apparent anti-sigma factor and is located immediately downstream ofSCE59.13c, renamed here sigU, whose product is inferred to be a member of the extracytoplasmic function subfamily of RNA polymerase sigma factors. The absence ofrsuA in a strain that contained sigUcaused a block in development, and the overexpression ofsigU in an otherwise wild-type strain caused a delay in aerial mycelium formation. However, a strain in which bothrsuA and sigU had been deleted was able to undergo morphological differentiation normally. We conclude that thersuA-encoded anti-sigma factor is responsible for antagonizing the function of the sigma factor encoded bysigU. We also conclude that thesigU-encoded sigma factor is not normally required for development but that its uncontrolled activity obstructs morphological differentiation at an early stage.

Download Full-text