Chromosomal organization governs the timing of cell type-specific gene expression required for spore formation in Bacillus subtilis

Mol Microbiol. 2001 Mar;39(6):1471-81. doi: 10.1046/j.1365-2958.2001.02331.x.

Abstract

During the early stages of spore formation in Bacillus subtilis, asymmetric division precedes chromosome segregation, such that the forespore transiently contains only about one-third of the genetic material surrounding the origin of replication. Shortly after septum formation, the transcription factor sigmaF initiates forespore-specific gene expression that is essential for the proteolytic activation of pro-sigmaE in the neighbouring mother cell. Moving the sigmaF-dependent spoIIR gene from its original origin-proximal position to an ectopic origin-distal site caused a delay in spoIIR transcription, as well as delays and reductions in the proteolytic activation of pro-sigmaE and sigmaE-directed gene expression. These defects correlated with the accumulation of disporic sporangia, thus reducing sporulation efficiency in a manner that depended upon the distance that spoIIR had been moved from the origin-proximal third of the chromosome. A significant proportion of disporic sporangia exhibited sigmaE activity in their central compartment, indicating that delays and reductions in sigmaE activation can lead to the formation of a second septum at the opposite pole. These observations support a model in which chromosomal spoIIR position temporally regulates sigmaE activation, thereby allowing for the rapid establishment of mother cell-specific gene expression that is essential for efficient spore formation. The implications of these findings for cell type-specific gene expression during the early stages of spore formation in B. subtilis are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus subtilis / physiology*
  • Bacterial Proteins / genetics*
  • Chromosomes, Bacterial*
  • Gene Expression Regulation, Bacterial*
  • Sigma Factor / genetics
  • Spores, Bacterial / genetics
  • Transcription Factors / genetics
  • Transcription, Genetic

Substances

  • Bacterial Proteins
  • FliA protein, Bacteria
  • Sigma Factor
  • Transcription Factors
  • spoIIR protein, Bacillus subtilis
  • spore-specific proteins, Bacillus
  • sporulation-specific sigma factors