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Temporal and spatial control of fungal filamentous growth in Candida albicans

Abstract : Candida albicans is a fungal human pathogen that can cause life-threatening infections in immunocompromised patients, in part, due to its ability to switch between an oval budding form and a filamentous hyphal form. The small-Rho GTPase Cdc42 is crucial for filamentous growth and, in its active form, localizes as a tight cluster at the tips of growing hyphae. I have used a light-activated membrane recruitment system comprised of the Arabidopsis thaliana Cry2PHR-CibN domains to control the recruitment of constitutively active Cdc42 to the plasma membrane. I have determined how photorecruitment of constitutively active Cdc42 perturbs filamentous growth and where, when and how new filamentous growth is subsequently initiated. My results demonstrate that, upon photorecruitment of constitutively active Cdc42, filament extension is abrogated and a new growth site can be established in the cell. Location of a new filamentous growth site correlates with the length of the initial filament. I have investigated the molecular mechanisms that underlie the disassembly of an initial growth site and the specific location of the new filamentous growth site. In growing hyphae a cluster of vesicles, referred to as a Spitzenkörper, is localized at the tip of the filament. Upon photorecruitment of constitutively active Cdc42, a new cluster of vesicles, with a composition similar to that of the initial Spitzenkörper, appears in the mother cell. I have followed the dynamics of the Spitzenkörper, active Cdc42, sites of endocytosis, secretory vesicles and actin cables subsequent to disruption of the initial growth site in the filament. Taken together, my results suggest that there is competition for growth between the Spitzenkörper and the cluster of vesicles that forms immediately after the photorecruitment of constitutively active Cdc42 and that a dynamic polarity axis can be established in the absence of directional growth.
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Patricia Maria de Oliveira E Silva. Temporal and spatial control of fungal filamentous growth in Candida albicans. Cellular Biology. Université Côte d'Azur, 2018. English. ⟨NNT : 2018AZUR4030⟩. ⟨tel-02615585⟩

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