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Abstract
The filamentous fungus Aspergillus nidulans is an excellent model system for exploring basic eukaryotic cell biology. In this dissertation A. nidulans is used to better understand nuclei and the septin cytoskeleton. This work includes a study of the movement of histone proteins between nuclei within heterokaryon colonies. This study provided evidence that histone H1 can move freely between genetically distinct nuclei within and across cellular compartments. It also showed how proteins derived from a single nucleus within phialide cells of a conidiophore may partition themselves during sporulation, a process which was unclear. The septin cytoskeleton has been best studied in the yeast S. cerevisiae. In this work all published single point mutations and associated phenotypes of the seven S. cerevisiae septin genes were analyzed. The mutations were systematically mapped onto aligned amino acid residues, interface regions between septin monomers, as well as beta sheets and alpha helices of the mammalian crystal structure, orthologous to Cdc3AspB. This analysis showed that most temperature sensitive mutations in the literature are in the G interface region. The many roles of septins in scaffolding proteins and providing the framework for growth are still not fully elucidated in filamentous fungi. The final study in this dissertation investigates possible roles that septins may share in maintaining cell wall integrity
through the cell wall integrity MAPK signaling pathway, and the involvement of sphingolipid and ergosterol metabolism which may contribute to this process. This study also provides a working model for how this mechanism might occur in A. nidulans.
through the cell wall integrity MAPK signaling pathway, and the involvement of sphingolipid and ergosterol metabolism which may contribute to this process. This study also provides a working model for how this mechanism might occur in A. nidulans.