Identification of Bacillus subtilis genes expressed early during sporulation.

Labelled cDNA transcribed in vitro from early-sporulation RNA was enriched for sporulation-specific sequences by subtractive hybridization to an excess of vegetative RNA and used to probe libraries of Bacillus subtilis chromosomal DNA. From the initial collection of clones that coded for RNAs transcribed preferentially during sporulation, several were subcloned and studied in more detail. It was found that two clones contained sequences (dciA and dciB) that had an undetectable level of transcription during vegetative growth but had transcripts that started to appear no later than eight minutes after induction of sporulation. A third DNA segment (dciC) was expressed at a low level in vegetative cells and increased within four minutes after induction of sporulation. The effects of spoO mutations, i.e. mutations that prevent cells from reaching stage I of the sporulation process, were tested. Induction of the dciA and dciB transcripts was significantly reduced in strains carrying mutations in the spoOA and spoOH genes but not in a spoOB mutant strain. In addition, a product of the abrB locus, a locus in which mutations are known to partially overcome the pleiotropic effect of spoOA and spoOB mutations, seemed to be required for dciA and dciB expression.