The Chromosomal Location of the Bacillus subtilis Sporulation Gene spoIIR Is Important for Its Function

Formation of the asymmetrically located septum during sporulation of Bacillus subtilis results in enclosure of the origin-proximal 30% of the chromosome in the prespore compartment. The rest of the chromosome is then translocated into the prespore from the mother cell. Transcription of spoIIR is initiated in the prespore by RNA polymerase containing ς(F) soon after the septum is formed. The SpoIIR protein is required for the activation of the transcription program directed by ς(E) in the mother cell. The spoIIR locus is located at 324°, near the origin of replication (0/360°). We show here that movement of spoIIR to 28° had little effect on sporulation. However, movement to regions not in the origin-proximal part of the chromosome substantially reduced sporulation efficiency. At 283° sporulation was reduced to less than 20% of the level obtained when spoIIR was at its natural location, and movement to 190° reduced sporulation to about 6% of that level. These positional effects were also seen in the transcription of a spoIIR-lacZ fusion. In contrast, movement of other spo-lacZ fusions from 28° to 190° had little effect on their expression. These results suggest that spoIIR is the subject of “positional regulation,” in the sense that the chromosomal position of spoIIR is important for its expression and function.