A feedback loop regulates the switch from one sigma factor to the next in the cascade controlling Bacillus subtilis mother cell gene expression.

ABSTRACT In the mother cell of sporulating Bacillus subtilis, a regulatory network functions to control gene expression. Four transcription factors act sequentially in the order σE, SpoIIID, σK, GerE. σE and σK direct RNA polymerase to transcribe different regulons. SpoIIID and GerE are DNA-binding proteins that activate or repress transcription of many genes. Several negative regulatory loops add complexity to the network. First, transcriptionally active σK RNA polymerase inhibits early sporulation gene expression, resulting in reduced accumulation of σE and SpoIIID late during sporulation. Second, GerE represses sigK transcription, reducing σK accumulation about twofold. Third, SpoIIID represses cotC, which encodes a spore coat protein, delaying its transcription by σK RNA polymerase. Partially circumventing the first feedback loop, by engineering cells to maintain the SpoIIID level late during sporulation, causes spore defects. Here, the effects of circumventing the second feedback loop, by mutating the GerE binding sites in the sigK promoter region, are reported. Accumulation of pro-σK and σK was increased, but no spore defects were detected. Expression of σK-dependent reporter fusions was altered, increasing the expression of gerE-lacZ and cotC-lacZ and decreasing the expression of cotD-lacZ. Because these effects on gene expression were opposite those observed when the SpoIIID level was maintained late during sporulation, cells were engineered to both maintain the SpoIIID level and have elevated sigK expression late during sporulation. This restored the expression of σK-dependent reporters to wild-type levels, and no spore defects were observed. Hence, circumventing the second feedback loop suppressed the effects of perturbing the first feedback loop. By feeding information back into the network, these two loops appear to optimize target gene expression and increase network robustness. Circumventing the third regulatory loop, by engineering cells to express cotC about 2 h earlier than normal, did not cause a detectable spore defect.

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Maintaining the Transcription Factor SpoIIID Level Late during Sporulation Causes Spore Defects in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.00839-07 ◽

2007 ◽

Vol 189 (20) ◽

pp. 7302-7309 ◽

Cited By ~ 4

Author(s):

Lijuan Wang ◽

John Perpich ◽

Adam Driks ◽

Lee Kroos

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Rna Polymerase ◽

Mother Cell ◽

Structural Defects ◽

Spore Coat ◽

Multicopy Plasmid ◽

Altered Expression ◽

Cell Gene Expression ◽

Cell Gene

ABSTRACT During sporulation of Bacillus subtilis, four regulatory proteins act in the order σE, SpoIIID, σK, and GerE to temporally control gene expression in the mother cell. σE and σK work sequentially with core RNA polymerase to transcribe different sets of genes. SpoIIID and GerE are small, sequence-specific DNA-binding proteins that activate or repress transcription of many genes. Previous studies showed that transcriptionally active σK RNA polymerase inhibits early mother cell gene expression, reducing accumulation of SpoIIID late in sporulation. Here, the effects of perturbing the mother cell gene regulatory network by maintaining the SpoIIID level late during sporulation are reported. Persistent expression was obtained by fusing spoIIID to the σK-controlled gerE promoter on a multicopy plasmid. Fewer heat- and lysozyme-resistant spores were produced by the strain with persistent spoIIID expression, but the number of spores resistant to organic solvents was unchanged, as was their germination ability. Transmission electron microscopy showed structural defects in the spore coat. Reporter fusions to σK-dependent promoters showed lower expression of gerE and cotC and higher expression of cotD. Altered expression of cot genes, which encode spore coat proteins, may account for the spore structural defects. These results suggest that one role of negative feedback by σK RNA polymerase on early mother cell gene expression is to lower the level of SpoIIID late during sporulation in order to allow normal expression of genes in the σK regulon.

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Expression of spoIIIJ in the Prespore Is Sufficient for Activation of σG and for Sporulation in Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.185.13.3905-3917.2003 ◽

2003 ◽

Vol 185 (13) ◽

pp. 3905-3917 ◽

Cited By ~ 27

Author(s):

Mónica Serrano ◽

Luísa Côrte ◽

Jason Opdyke ◽

Charles P. Moran, ◽

Adriano O. Henriques

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Rna Polymerase ◽

Sigma Factor ◽

Vegetative Growth ◽

Mother Cell ◽

Asymmetric Division ◽

Developmental Program ◽

Inactive Form

ABSTRACT During sporulation in Bacillus subtilis, the prespore-specific developmental program is initiated soon after asymmetric division of the sporangium by the compartment-specific activation of RNA polymerase sigma factor σF. σF directs transcription of spoIIIG, encoding the late forespore-specific regulator σG. Following synthesis, σG is initially kept in an inactive form, presumably because it is bound to the SpoIIAB anti-sigma factor. Activation of σG occurs only after the complete engulfment of the prespore by the mother cell. Mutations in spoIIIJ arrest sporulation soon after conclusion of the engulfment process and prevent activation of σG. Here we show that σG accumulates but is mostly inactive in a spoIIIJ mutant. We also show that expression of the spoIIIGE155K allele, encoding a form of σG that is not efficiently bound by SpoIIAB in vitro, restores σG-directed gene expression to a spoIIIJ mutant. Expression of spoIIIJ occurs during vegetative growth. However, we show that expression of spoIIIJ in the prespore is sufficient for σG activation and for sporulation. Mutations in the mother cell-specific spoIIIA locus are known to arrest sporulation just after completion of the engulfment process. Previous work has also shown that σG accumulates in an inactive form in spoIIIA mutants and that the need for spoIIIA expression for σG activation can be circumvented by the spoIIIGE155K allele. However, in contrast to the case for spoIIIJ, we show that expression of spoIIIA in the prespore does not support efficient sporulation. The results suggest that the activation of σG at the end of the engulfment process involves the action of spoIIIA from the mother cell and of spoIIIJ from the prespore.

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Overproducing the Bacillus subtilis mother cell sigma factor precursor, Pro-sigma K, uncouples sigma K-dependent gene expression from dependence on intercompartmental communication.

Journal of Bacteriology ◽

10.1128/jb.176.13.3936-3943.1994 ◽

1994 ◽

Vol 176 (13) ◽

pp. 3936-3943 ◽

Cited By ~ 14

Author(s):

S Lu ◽

L Kroos

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Sigma Factor ◽

Mother Cell

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The Timing of cotE Expression Affects Bacillus subtilis Spore Coat Morphology but Not Lysozyme Resistance

Journal of Bacteriology ◽

10.1128/jb.01353-06 ◽

2006 ◽

Vol 189 (6) ◽

pp. 2401-2410 ◽

Cited By ~ 21

Author(s):

Teresa Costa ◽

Mónica Serrano ◽

Leif Steil ◽

Uwe Völker ◽

Charles P. Moran ◽

...

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Mother Cell ◽

Spore Coat ◽

Outer Coat ◽

Bacillus Subtilis Spore ◽

Spore Resistance ◽

Early Expression ◽

Cell Gene Expression ◽

Coat Layer

ABSTRACT The synthesis of structural components and morphogenetic factors required for the assembly of the Bacillus subtilis spore coat is governed by a mother cell-specific transcriptional cascade. The first two temporal classes of gene expression, which involve RNA polymerase sigma σE factor and the ancillary regulators GerR and SpoIIID, are deployed prior to engulfment of the prespore by the mother cell. The two last classes rely on σK, whose activation follows engulfment completion, and GerE. The cotE gene codes for a morphogenetic protein essential for the assembly of the outer coat layer and spore resistance to lysozyme. cotE is expressed first from a σE-dependent promoter and, in a second stage, from a promoter that additionally requires SpoIIID and that remains active under σK control. CotE localizes prior to engulfment completion close to the surface of the developing spore, but formation of the outer coat is a late, σK-controlled event. We have transplanted cotE to progressively later classes of mother cell gene expression. This created an early class of mutants in which cotE is expressed prior to engulfment completion and a late class in which expression of cotE follows the complete engulfment of the prespore. Mutants of the early class assemble a nearly normal outer coat structure, whereas mutants of the late class do not. Hence, the early expression of CotE is essential for outer coat assembly. Surprisingly, however, all mutants were fully resistant to lysozyme. The results suggest that CotE has genetically separable functions in spore resistance to lysozyme and spore outer coat assembly.

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ςK Can Negatively RegulatesigE Expression by Two Different Mechanisms during Sporulation of Bacillus subtilis

Journal of Bacteriology ◽

10.1128/jb.181.13.4081-4088.1999 ◽

1999 ◽

Vol 181 (13) ◽

pp. 4081-4088 ◽

Cited By ~ 23

Author(s):

Bin Zhang ◽

Paolo Struffi ◽

Lee Kroos

Keyword(s):

Bacillus Subtilis ◽

Rna Polymerase ◽

Sigma Factor ◽

Mother Cell ◽

Transcriptional Activity ◽

The Other ◽

Mutant Form ◽

Gene Encoding ◽

Negative Effect ◽

Cell Gene Expression

ABSTRACT Temporal and spatial gene regulation during Bacillus subtilis sporulation involves the activation and inactivation of multiple sigma subunits of RNA polymerase in a cascade. In the mother cell compartment of sporulating cells, expression of thesigE gene, encoding the earlier-acting sigma factor, ςE, is negatively regulated by the later-acting sigma factor, ςK. Here, it is shown that the negative feedback loop does not require SinR, an inhibitor of sigEtranscription. Production of ςK about 1 h earlier than normal does affect Spo0A, which when phosphorylated is an activator of sigE transcription. A mutation in thespo0A gene, which bypasses the phosphorelay leading to the phosphorylation of Spo0A, diminished the negative effect of early ςK production on sigE expression early in sporulation. Also, early production of ςK reduced expression of other Spo0A-dependent genes but not expression of the Spo0A-independent ald gene. In contrast, bothsigE and ald were overexpressed late in development of cells that fail to make ςK. Theald promoter, like the sigE promoter, is believed to be recognized by ςA RNA polymerase, suggesting that ςK may inhibit ςA activity late in sporulation. To exert this negative effect, ςKmust be transcriptionally active. A mutant form of ςKthat associates with core RNA polymerase, but does not direct transcription of a ςK-dependent gene, failed to negatively regulate expression of sigE or aldlate in development. On the other hand, the negative effect of early ςK production on sigE expression early in sporulation did not require transcriptional activity of ςK RNA polymerase. These results demonstrate that ςK can negatively regulate sigE expression by two different mechanisms, one observed when ςK is produced earlier than normal, which does not require ςKto be transcriptionally active and affects Spo0A, and the other observed when ςK is produced at the normal time, which requires ςK RNA polymerase transcriptional activity. The latter mechanism facilitates the switch from ςE to ςK in the cascade controlling mother cell gene expression.

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Role of the Anti-Sigma Factor SpoIIAB in Regulation of σG during Bacillus subtilis Sporulation

Journal of Bacteriology ◽

10.1128/jb.186.12.4000-4013.2004 ◽

2004 ◽

Vol 186 (12) ◽

pp. 4000-4013 ◽

Cited By ~ 27

Author(s):

Mónica Serrano ◽

Alexandre Neves ◽

Cláudio M. Soares ◽

Charles P. Moran ◽

Adriano O. Henriques

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Sigma Factor ◽

Mother Cell ◽

In Vivo Studies ◽

Specific Gene ◽

Rapid Induction ◽

Inactive Form ◽

Entire Cell

ABSTRACT RNA polymerase sigma factor σF initiates the prespore-specific program of gene expression during Bacillus subtilis sporulation. σF governs transcription of spoIIIG, encoding the late prespore-specific regulator σG. However, transcription of spoIIIG is delayed relative to other genes under the control of σF, and after synthesis, σG is initially kept in an inactive form. Activation of σG requires the complete engulfment of the prespore by the mother cell and expression of the spoIIIA and spoIIIJ loci. We screened for random mutations in spoIIIG that bypassed the requirement for spoIIIA for the activation of σG. We found a mutation (spoIIIGE156K) that resulted in an amino acid substitution at position 156, which is adjacent to the position of a mutation (E155K) previously shown to prevent interaction of SpoIIAB with σG. Comparative modelling techniques and in vivo studies suggested that the spoIIIGE156K mutation interferes with the interaction of SpoIIAB with σG. The σGE156K isoform restored σG-directed gene expression to spoIIIA mutant cells. However, expression of sspE-lacZ in the spoIIIA spoIIIGE156K double mutant was delayed relative to completion of the engulfment process and was not confined to the prespore. Rather, β-galactosidase accumulated throughout the entire cell at late times in development. This suggests that the activity of σGE156K is still regulated in the prespore of a spoIIIA mutant, but not by SpoIIAB. In agreement with this suggestion, we also found that expression of spoIIIGE156K from the promoter for the early prespore-specific gene spoIIQ still resulted in sspE-lacZ induction at the normal time during sporulation, coincidently with completion of the engulfment process. In contrast, transcription of spoIIIGE156K, but not of the wild-type spoIIIG gene, from the mother cell-specific spoIID promoter permitted the rapid induction of sspE-lacZ expression. Together, the results suggest that SpoIIAB is either redundant or has no role in the regulation of σG in the prespore.

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A forespore checkpoint for mother cell gene expression during development in B. subtilis

Cell ◽

10.1016/0092-8674(90)90362-i ◽

1990 ◽

Vol 62 (2) ◽

pp. 239-250 ◽

Cited By ~ 118

Author(s):

Simon Cutting ◽

Valerie Oke ◽

Adam Driks ◽

Richard Losick ◽

Sijie Lu ◽

...

Keyword(s):

Gene Expression ◽

Mother Cell ◽

Cell Gene Expression ◽

Cell Gene

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Establishment of Prespore-Specific Gene Expression inBacillus subtilis: Localization of SpoIIE Phosphatase and Initiation of Compartment-Specific Proteolysis

Journal of Bacteriology ◽

10.1128/jb.180.13.3276-3284.1998 ◽

1998 ◽

Vol 180 (13) ◽

pp. 3276-3284 ◽

Cited By ~ 13

Author(s):

Peter J. Lewis ◽

Ling Juan Wu ◽

Jeffery Errington

Keyword(s):

Gene Expression ◽

Bacillus Subtilis ◽

Sigma Factor ◽

Mother Cell ◽

Immunofluorescence Microscopy ◽

The Other ◽

Specific Gene ◽

Specific Gene Expression

ABSTRACT Immunofluorescence microscopy was used to study the establishment of compartment-specific transcription during sporulation inBacillus subtilis. Analysis of the distribution of the anti-anti-sigma factor, SpoIIAA, in a variety of mutant backgrounds supports a model in which the SpoIIE phosphatase, which activates SpoIIAA by dephosphorylation, is sequestered onto the prespore face of the asymmetric septum. Thus, prespore-specific gene expression apparently arises as a result of the compartmentalization of SpoIIE protein. The results also suggest the existence of at least two compartment-specific programs of proteolysis, one dependent on the mother cell-specific sigma factor ςE and the other dependent on the prespore-specific sigma factor ςF.

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