DISAPPEARANCE OF THE SIGMA(E) TRANSCRIPTION FACTOR FROM THE FORESPOREAND 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 govern ing the establishment of cell-specific gene transcription during sporu lation in the bacterium Bacillus subtilis. The transcription factors s igma(E) and sigma(F) are synthesized shortly after the start of sporul ation but do not become active in directing gene transcription until a fter polar division, when the activity of sigma(E) is confined to the mother cell and the activity of sigma(F) is restricted to the forespor e. We show that shortly after septation, sigma(E) and its proprotein p recursor 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 transl ocation 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. T hese 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. Her e we show that a null mutation in spoIIIE causes the SpoIIE phosphatas e 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 t hat the establishment of cell-specific gene transcription involves the loss of sigma E/pro-sigma(E) from the forespore and the loss of the S poIIE phosphatase from the mother-cell pole and that both processes ar e dependent upon the SpoIIIE protein.