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Abstract
Upon germination, filamentous fungi grow mainly by tip extension after brief isotropic expansion. This dissertation uses Aspergillus nidulans as a model organism to study genes that are involved in polar growth by a forward genetics approach. Two temperature sensitive mutants, swoC1 and swoH1, defective in polarity establishment and maintenance were characterized. Both genes were genetically mapped and cloned. The swoC gene encodes an rRNA pseudouridine synthase (AnCBF5) and the swoH gene encodes a nucleoside diphosphate kinase (NDK). Null mutants of swoC and swoH genes were lethal in A. nidulans. Although both genes have been considered hous ekeeping genes, recent evidence from this and other studies suggests that they have more complex roles. Possible biological functions of SwoCp in nuclear positioning and polarity establishment, and SwoHp in stress attenuation in Aspergillus nidulans are discussed.