CELL-TYPE SPECIFICITY DURING DEVELOPMENT IN BACILLUS-SUBTILIS - THE MOLECULAR AND MORPHOLOGICAL REQUIREMENTS FOR SIGMA(E) ACTIVATION

Development in Bacillus subtilis involves the formation of two cell ty pes with activation of the transcription factors sigma(F) in the fores pore and sigma(E) in the mother cell. Activation of sigma(E) is due to the processing of the inactive precursor pro-sigma(E), which requires the putative protease SpoIIGA and the presence of active sigma(F). We have introduced missense mutations altering the promoter recognition properties of sigma(F). These mutations abolish pro-sigma(E) processin g, suggesting that sigma(F) is involved through its transcriptional ac tivity and that the processing machinery responds to a signal generate d by the product(s) of some unidentifed gene(s) transcribed in the for espore. The role of the septum in transducing this signal was investig ated. Induction of sigma(F) during exponential growth in cells produci ng SpoIIGA and pro-sigma(E) led to a high level of processing and sigm a(E) activity. Moreover, pro-sigma(E) was efficiently processed in a m utant strain blocked prior to septation and synthesizing sigma(F) in a ctive form at the onset of sporulation. Therefore, the sporulation sep tum is not required for induction of pro-sigma(E) processing and pro-s igma(E) can be processed in the same cell in which sigma(F) is active. These results suggest that some unknown mechanism must exist to preve nt sigma(E) from becoming active in the forespore.