How the early sporulation sigma factor σ^F delays the switch to late development in Bacillus subtilis

Abstract

SummarySporulation in Bacillus subtilis is a primitive differentiation process involving two cell types, the forespore and the mother cell. Each cell implements two successive transcription programmes controlled by specific sigma factors. We report that activity of s G , the late forespore sigma factor, is kept in check by Gin, the product of csfB, a gene controlled by s F , the early forespore sigma factor. Gin abolishes s G transcriptional activity when s G is artificially synthesized during growth, but has no effect on s F . Gin interacts strongly with s G but not with s F in a yeast two-hybrid experiment. The absence of Gin allows s G to be active during sporulation independently of the mother-cell development to which it is normally coupled. Premature s G activity leads to the formation of slowgerminating spores, and complete deregulation of s G synthesis is lethal when combined with gin inactivation. Gin allows s F to delay the switch to the late forespore transcription programme by preventing s G to take over before the cell has reached a critical stage of development. A similar strategy, following a completely unrelated route, is used by the mother cell.

Loss of Compartmentalization of σ E Activity Need Not Prevent Formation of Spores by Bacillus subtilis

“…CsfB also acts to curtail the activity of E *, which is active without processing. We think it plausible that, by analogy with its action on G (1,6,26), CsfB directly inhibits E activity. That is to say, CsfB inhibits the activity of two sigma factors.…”

“…The csfB locus is transcribed in the prespore from a F -directed promoter (7). The CsfB protein has been shown to inhibit premature activation of G in the prespore (1,6,26). CsfB can also impair E activity (6).…”

Sporulation and Enterotoxin (CPE) Synthesis Are Controlled by the Sporulation-Specific Sigma Factors SigE and SigK inClostridium perfringens

“…SpoIIAB and another anti-sigma factor, CsfB, can also act as anti-sigma factors to suppress low levels of inappropriate G activity, but the mechanism of G activation to completion of forespore engulfment remains speculative (6,7,34,35).…”

Coupling of σ G Activation to Completion of Engulfment during Sporulation of Bacillus subtilis Survives Large Perturbations to DNA Translocation and Replication

“…Transcription of csfB is initially directed by the prespore-specific factor F (13,42) and subsequently by G , indicating complex regulatory circuits (42). Deletion of csfB results in a low level of G activity in the prespore prior to the completion of engulfment but does not affect the large increase in G activity that follows completion of engulfment (11,26,42). Thus, CsfB is inadequate to explain the postengulfment activation of G .…”

“…They do not signal activation at the correct time. Of the three proteins, CsfB has the most prominent role in that it prevents premature activation of G in the prespore (5,11,26,42). Transcription of csfB is initially directed by the prespore-specific factor F (13,42) and subsequently by G , indicating complex regulatory circuits (42).…”