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Overlapping SigH and SigE sigma factor regulons in Corynebacterium glutamicum
Tobias Busche1,2, Hana Dostálová3, Lenka Rucká3
1Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
Frontiers in Microbiology
|March 17, 2023
Summary
This study reveals significant overlap between the sigma H (σΗ) and sigma E (σE) regulons in Corynebacterium glutamicum, uncovering genes involved in cell surface stress response and protein quality control. Promoter analysis identified distinct regulatory mechanisms for these sigma factors.
Area of Science:
- Microbiology and Molecular Biology
- Bacterial Stress Response Mechanisms
- Gene Regulation in *Corynebacterium glutamicum*
Background:
- Sigma factors σΗ and σE in *Corynebacterium glutamicum* are Group 4 extracytoplasmic function (ECF) sigma factors.
- The σΗ regulon's role in heat and oxidative stress is known, but the σE regulon's involvement in cell surface stress response remains unexplored.
- Understanding these regulons is crucial for elucidating bacterial adaptation and survival strategies.
Purpose of the Study:
- To explore and define the genes regulated by the σE regulon in *Corynebacterium glutamicum*.
- To investigate the overlap and differences between the σΗ and σE regulons.
- To identify the promoter sequences and specific interactions governing σΗ and σE-dependent gene expression.
Main Methods:
- Differential gene expression analysis using RNA sequencing in wild-type and ΔcseE mutant strains of *C. glutamicum*.
- Validation of promoter activity using an *in vivo* two-plasmid system with a *gfp*uv reporter gene.
- *In vitro* transcription assays with purified RNA polymerase (RNAP) and σΗ or σE, coupled with homology modeling for protein-DNA interactions.
Main Results:
- RNA sequencing identified 296 upregulated and 398 downregulated genes in the ΔcseE mutant, indicating extensive σE-mediated regulation.
- Significant overlap was observed between σΗ and σE regulons, with identified σE-controlled genes involved in protein quality control and membrane integrity.
- Promoter analysis revealed two types: exclusively σΗ-specific and σΗ/σE-dependent promoters, with defined consensus sequences and specific amino acid interactions (Met170 in σΗ, Arg185 in σE) at key promoter regions.
Conclusions:
- The σE regulon plays a significant role in *C. glutamicum*'s cell surface stress response, overlapping substantially with the σΗ regulon.
- Gene expression is controlled by distinct promoter elements recognized differently by σΗ and σE, highlighting a nuanced regulatory network.
- This study provides a comprehensive definition of the σE regulon and its interplay with σΗ, advancing our understanding of bacterial stress adaptation.
Keywords:
CorynebacteriumRNA-seqconsensus sequencepromoterregulonsigma factorstresstranscriptional start siteMore Related Videos
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