Cell-cell signaling pathway activating a developmental transcription factor in Bacillus subtilis.

Transcription in the mother cell at early stages of sporulation in Bacillus subtilis is controlled by sigma E, a sigma factor that is synthesized in the predivisional cell as an inactive larger precursor, pro-sigma E. Activation of sigma E depends on sigma F, the factor that governs transcription in the forespore. Genetic experiments have indicated that transduction of the activation signal from the forespore to the mother cell requires the products of some genes belonging to the sigma F-controlled regulon. We have identified and characterized a sigma F-dependent gene, csfX, encoding a protein necessary and sufficient for triggering processing of pro-sigma E. The CsfX protein contains a typical amino-terminal signal sequence suggesting that, although synthesized in the forespore, it may act across the septum to activate the membrane-bound enzyme that is responsible for pro-sigma E processing in the mother cell.