A DEVELOPMENTAL CHECKPOINT COUPLES THE INITIATION OF SPORULATION TO DNA-REPLICATION IN BACILLUS-SUBTILIS

Spore formation in Bacillus subtilis requires the generation of two di stinct cell types, each with an active chromosome that becomes committ ed to a definedprogram of gene expression. Here H e show that a develo pmental checkpoint couples the initiation of sporulation, and the subs equent formation of these two cell types, to DNA replication early dur ing development. Inhibiting the initiation of chromosomal replication prevents the onset of sporulation and inhibitsexpression of several ge nes that are normally induced early during development. This defect in gene expression is due to inhibition of the multi-component phosphory lation pathway needed to activate the developmental transcription fact or encoded by spoOA. The target affected by inhibiting the initiation of replication is neither SpoOA nor the major kinase, KinA, needed for production of SpoOA similar to P. Rather, the target appears to be on e of the proteins that transfers phosphate from the kinase to the SpoO A transcription factor. The signal that couples activity of the phosph orelay to the initiation of DNA replication is different from the prev iously described DNA damage signal that inhibits the phosphorelay duri ng SOS induction in a recA-dependent response. Thus, DNA replication a s well as DNA damage signals control production of SpoOA similar to P and initiation of sporulation.