The Aspergillus nidulans septin AspB plays important roles in septum, branch, and conidiophore development
Westfall, Patrick John
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The septin family of proteins acts as an organizational scaffold in areas of cell division and new growth. Originally discovered in Saccharomyces cerevisiae, septins have also been characterized in numerous other organisms such as fruit flies, mice, and humans. In S. cerevisiae, septins were first described as a series of 10nm filamentous rings found at the neck of a budding cell. Septins play a role in such processes as cytokinesis, bud site selection, polarity establishment, and spore formation. Five septin homologues have been found in the filamentous fungus, Aspergillus nidulans. This dissertation focuses on the characterization of one of these, AspB. Null alleles of aspB are lethal. Localization studies using polyclonal antibodies show that AspB localizes to the site of cytokinesis in a distinctive, polar pattern as the septum develops. AspB also marks the site of branch emergence and localizes to specific interfaces as the asexual reproductive structure forms. In order to further understand the role of AspB in A. nidulans development, conditional mutants were generated and, based on phenotypic studies, support a role for AspB in septum formation, branch initiation, and asexual development.