GENE EXPRESSION DURING SPORULATION

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Formation of spores by Bacillus subtilis is a primitive system of cell differentiation. A crucial early stage of sporulation is an asymmetrically located division. This gives rise to two distinct cell types, the mother cell and the prespore which have radically different developmental fates. The mother cell is required for the development but ultimately lyses. Spore formation requires a complex pattern of gene expression. The main problem being addressed here is how that complex pattern is orchestrated during the developmental transition from the single-cell state tot he engulfment of the prespore by the mother cell. This includes questions of compartmentalization of gene expression and coordination of gene expression with morphological changes. The spoIIA and spoIIG loci occupy a pivotal position in spore formation. They include the structural genes for the RNA polymerase sigma factors F and E, respectively. The loci are transcribed before the septum is formed. The sigma factors may be activated by septum formation. Their activities are initially not compartmentalized, but become compartmentalized, with F being active in the prespore and E in the mother cell. SigmaF and sigmaE are thought to be required, directly or indirectly, for the transcription of all later expressed sporulation genes. It is proposed to identify genes involved in the activation of sigmaF and sigmaE, and to characterize those genes as well as a gene, spoIIR, that we have recently identified as being required for processing of pro-sigmaE to sigmaE. It is proposed to investigate the compartmentalization of gene expression, and to identify and study genes required for compartmentalization. it is proposed to investigate genes transcribed by EsigmaF. It is also proposed to investigate the controls of IIA transcription, taking account of the possibilities of redundancies and feed back loops in the controls.