A cloned gene that is turned on at an intermediate stage of spore formation in Bacillus subtilis

Cells of Bacillus subtilis synthesize a relatively long-lived ribonucleic acid (RNA) of about 300 bases during the course of spore formation. This transcript does not appear until an intermediate stage (III or IV) of development but is the predominant sporulation-specific transcript among RNAs of discrete size in late (stages IV to VI) developing cells. Appearance of the 300-base RNA is under sporulation control as this transcript could not be detected in cells of an early-blocked sporulation mutant (Spo0A). We have located the coding sequence for the 300-base RNA within a cloned chromosomal segment from the purA-cysA region that was previously shown to contain a cluster of genes that are actively transcribed during sporulation. The coding sequence for the 300-base RNA (designated as the 0.3 kb gene) mapped between a gene (veg) that was actively transcribed during growth and development and a gene (0.4 kb) that was turned on at the onset of sporulation. Although clustered within a small segment of the chromosome, the veg, 0.3 kb, and 0.4 kb transcription units exhibited, therefore, distinct patterns of temporally programmed gene expression. Models for the activation of the 0.3 kb gene at an intermediate stage of development are discussed.