Aspergillus nidulans swoQ Plays an Important Role in Polarized Hyphal Growth
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Filamentous fungi form polarized hyphae by concentrating the addition of new material at the apex of the cell. The mechanics of polarized hyphal growth are coordinated by the cytoskeleton which utilizes microtubules (MTs) and filamentous actin in order to facilitate vesicle trafficking. The cytoskeletal machinery implicated in the regulation of endocytosis and exocytosis during polarized growth is complex and has been studied extensively in recent years. Despite these efforts there are many gaps in the current growth model, and the exact role of the cytoskeleton on secretion and internalization mechanisms during polarized growth remains to be elucidated. In order to address this knowledge gap, this study investigates the contribution of cytoskeletal elements on polarized growth. In this study, I identified the Aspergillus nidulans temperature-sensitive (TS) mutant, swoQ. A mutant allele in the swoQ gene results in abnormal polarity maintenance and cell morphogenesis in the swoQ strain, as evidenced by the presence of abnormally swollen cells. A forward genetic screen revealed the swoQ polarity defect was suppressed following transformation with the pRG3-47-1 library plasmid which encodes myoA, a class I myosin motor protein. A sub-clone of myoA was introduced into the swoQ mutant and wild-type which resulted in restoration of polarized growth in the polarity mutant and hyper-branching in both strains. To further assess the influence of swoQ, the localization of various polarity markers including: FimA::GFP, Exo84::GFP, DnfA::GFP, and DnfB::GFP, were examined in the mutant strain. The localization of FimA::GFP and Exo84::GFP was abnormal in the swoQ mutant. FimA is an actin nucleating protein which works alongside MyoA, an essential myosin in A. nidulans. Together these proteins facilitate the formation of actin patches which drive endocytosis. Here I show that overexpression of MyoA has a polarization effect on growing cells and is able to suppress the growth defect of the swoQ mutant.
Bomer, Brigitte (2016). Aspergillus nidulans swoQ Plays an Important Role in Polarized Hyphal Growth. Master's thesis, Texas A & M University. Available electronically from