Disappearance of the sE 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 sE and sF 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 sE is confined to the mother cell and the activity of sF is restricted to the forespore. We show that shortly after septation, sE and its proprotein precursor pro-sE 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 sE and/or pro-sE to persist and sE to become active in the forespore. These findings suggest that the loss of sE/pro-sE from the forespore contributes to the compartmentalization of sE-directed gene transcription. We also investigated the distribution of SpoIIE, a regulatory phosphatase required for the activation of sF 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 sF activity observed in a spoIIIE null mutant. We conclude that the establishment of cell-specific gene transcription involves the loss of sE/pro-sE from the forespore an