Disappearance of the sigma E transcription factor from the forespore and the SpoIIE phosphatase from the mother cell contributes to establishment of cell-specific gene expression during sporulation in Bacillus subtilis.
We used immunofluorescence microscopy to investigate mechanisms governing the establishment of cell-specific gene transcription during sporulation in the bacterium Bacillus subtilis. The transcription factors sigma E and sigma F are synthesized shortly after the start of sporulation but do not become active in directing gene transcription until after polar division, when the activity of sigma E is confined to the mother cell and the activity of sigma F is restricted to the forespore. We show that shortly after septation, sigma E and its proprotein precursor pro-sigma E appear to be absent from the forespore and that a null mutation in spoIIIE, a gene known to be required for the translocation of a chromosome into the forespore, allows sigma E and/or pro-sigma E to persist and sigma E to become active in the forespore. These findings suggest that the loss of sigma E/pro-sigma E from the forespore contributes to the compartmentalization of sigma E-directed gene transcription. We also investigated the distribution of SpoIIE, a regulatory phosphatase required for the activation of sigma F which exhibits a bipolar pattern of localization shortly after the start of sporulation. Normally, SpoIIE rapidly disappears from the sporangium, first from the mother-cell pole and then from the forespore pole. Here we show that a null mutation in spoIIIE causes the SpoIIE phosphatase to persist at both poles. The persistence of the SpoIIE phosphatase at the mother-cell pole could explain the lack of compartmentalization of sigma F activity observed in a spoIIIE null mutant. We conclude that the establishment of cell-specific gene transcription involves the loss of sigma E/pro-sigma E from the forespore and the loss of the SpoIIE phosphatase from the mother-cell pole and that both processes are dependent upon the SpoIIIE protein.
Pogliano
K
K
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Hofmeister
A E
AE
Losick
R
R
D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics*; D002451:Cell Compartmentation / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D016254:Mutagenesis, Insertional; D010749:Phosphoprotein Phosphatases / Q000235:genetics* / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics* / Q000502:physiology; D013171:Spores, Bacterial / Q000201:enzymology / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
D001426:Bacterial Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus; C063202:sporulation-specific sigma factors; D010749:Phosphoprotein Phosphatases