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Maintaining the Transcription Factor SpoIIID Level Late during Sporulation Causes Spore Defects in Bacillus subtilis

Department of Microbiology and Molecular Genetics,¹ Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824,² Department of Microbiology and Immunology, Loyola University Medical Center, Maywood, Illinois 60153³

Received 30 May 2007/ Accepted 1 August 2007

During sporulation of Bacillus subtilis, four regulatory proteins act in the order ^E, SpoIIID, ^K, and GerE to temporally control gene expression in the mother cell. ^E and ^K work sequentially with core RNA polymerase to transcribe different sets of genes. SpoIIID and GerE are small, sequence-specific DNA-binding proteins that activate or repress transcription of many genes. Previous studies showed that transcriptionally active ^K RNA polymerase inhibits early mother cell gene expression, reducing accumulation of SpoIIID late in sporulation. Here, the effects of perturbing the mother cell gene regulatory network by maintaining the SpoIIID level late during sporulation are reported. Persistent expression was obtained by fusing spoIIID to the ^K-controlled gerE promoter on a multicopy plasmid. Fewer heat- and lysozyme-resistant spores were produced by the strain with persistent spoIIID expression, but the number of spores resistant to organic solvents was unchanged, as was their germination ability. Transmission electron microscopy showed structural defects in the spore coat. Reporter fusions to ^K-dependent promoters showed lower expression of gerE and cotC and higher expression of cotD. Altered expression of cot genes, which encode spore coat proteins, may account for the spore structural defects. These results suggest that one role of negative feedback by ^K RNA polymerase on early mother cell gene expression is to lower the level of SpoIIID late during sporulation in order to allow normal expression of genes in the ^K regulon.

Published ahead of print on 10 August 2007.

This article has been cited by other articles:

• Wang, L., Perpich, J., Driks, A., Kroos, L. (2007). One Perturbation of the Mother Cell Gene Regulatory Network Suppresses the Effects of Another during Sporulation of Bacillus subtilis. J. Bacteriol. 189: 8467-8473 [Abstract] [Full Text]