The objective of this project is to elucidate the mechanisms that govern cell-specific gene expression during the process of spore formation in the bacterium Bacillus subtilis. Sporulation involves the formation of an asymmetrically positioned septum. The septum divides the developing cell into a forespore and a mother cell, which follow dissimilar pathways of gene expression and differentiation. Asymmetric division involves the remodeling of sister chromosomes into an elongated DNA mass that is anchored to both poles of the developing cell and a switch in the site of formation of a cytokinetic structure called the Z ring, which is composed of the tubulin-like protein FtsZ. Experiments will be carried out to investigate the role of the developmental protein RacA in chromosome remodeling and the role of the FtsZ-associated protein SpollE in the formation of Z rings near the cell poles. The role of RacA in a checkpoint mechanism that links chromosome anchoring to polar division will also be investigated. The transcription factor sigmaF becomes active in the forespore just after the formation of the polar septum. Experiments will be carried out to investigate the coupling of sF activation to the formation of the polar septum via the SpollE protein. Experiments will also be carried out to investigate the hypothesis that the DNA-binding protein Spo0A, which controls entry into sporulation, becomes a mother-cell-specific transcription factor after asymmetric division and sets in motion the mother-cell-line of gene expression. The mechanism by which gene expression in the mother cell is linked to gene expression in the forespore via an intercellular signal transduction pathway involving a membrane-bound proprotein processing complex will be investigated. Other projects are directed at understanding mechanisms of protein subcellular localization, elucidating on a genome-wide basis the programs of gene expression in the forespore and the mother cell, and investigating newly discovered aspects of sporulation involving multicellular interactions. These goals address basic questions of differentiation and gene control that are common to developing systems of many kinds, including complex systems of normal and abnormal development in higher organisms.
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