Characterization of spoIVA, a sporulation gene involved in coat morphogenesis in Bacillus subtilis

Abstract

We report the cloning and characterization of the Bacillus subtilis sporulation locus spoIVA, mutations at which cause an unusual defect in spore formation in which the coat misassembles as swirls within the mother cell. We show that spoIVA is a single gene of 492 codons that is capable of encoding a polypeptide of 55 kDa.Transcription of spoIVA is induced at about the second hour of sporulation by the regulatory protein cE from two closely spaced promoters designated P1 and P2. Experiments in which the upstream promoter P1 was removed show that transcription of spolVA from P2 is sufficient for efficient spore formation. Based on these and other findings, we infer that the spoIVA gene product is a morphogenetic protein; we discuss its role in the deposition of coat polypeptides around the developing forespore.Spores of the gram-positive soil bacterium Bacillus subtilis are encased in a thick protein shell known as the coat (1,22,32,51). The coat is a complex structure composed of a dozen or more polypeptides that are arranged in an electron-dense outer layer and a lamellar inner layer. These layers protect the spore from certain bacteriocidal agents, such as lysozyme, and also play a role in the responsiveness of the spore to germinants. The coat is produced at a relatively late stage in the process of sporulation when the developing spore or forespore is present as a free protoplast within the mother cell chamber of the sporangium (28, 35). Just before the formation of the coat, a layer of cell wall-like material called the cortex is produced between the membranes that separate the forespore protoplast from the mother cell. Coat biogenesis occurs by the synthesis of the coat polypeptides within the mother cell and their deposition around the mother cell membrane that encases the forespore. Here we describe the characterization of a sporulation gene called spoIVA, mutations in which impair cortex formation and cause misassembly of the inner and outer coats as swirls within the mother cell (3,34,35) (Fig. 1)

Combined Action of Two Transcription Factors Regulates Genes Encoding Spore Coat Proteins of Bacillus subtilis

“…cotX mRNA was barely detectable at hour 4, rose to its maximum level at hour 5, and fell to a barely detectable level at hour 6. cotC mRNA was present at a low level at hour 3. The enzyme responsible for this low level of cotC transcription is unknown, but it could be E RNAP because E and K recognize similar sequences in cognate promoters (22,23). The cotC mRNA level increased at hour 5 and continued to rise until hour 7.…”

Characterization of bofA, a gene involved in intercompartmental regulation of pro-sigma K processing during sporulation in Bacillus subtilis

“…This 75-bp region (Fig. 2) contains at a spacing of 14 bp the sequences CATAag-T and GtcTAaa, which conform well (matching in five out of seven positions) and moderately well (matching in three out of seven positions), respectively, to the consensus -10 (CATACA-T) and -35 (kmATATT, where k is a T or a Gand m is a C or an A) sequences for oF-recognized promoters (24). Experiments by Ireton and Grossman (14) (1).…”

The dynamic spore

“…SpoIVA resides between the coat and cortex (22,23). As this location suggests, SpoIVA connects the coat to the spore surface; without it, the coat is built but is not attached to the spore (24)(25)(26). CotE is positioned at the inner coat͞outer coat interface (22).…”