Roles of Cytoskeletal Polarity in Fungal Spore Adhesion and Growth

Abstract

Filamentous fungi are complex microorganisms that reproduce via the production of spores and grow by producing elongated polarized cells called hyphae. Both processes are essential to the life cycle of these organisms. Spore production, dispersal, and adhesion are essential for dissemination of the organism. Spore adhesion is especially important to plant pathology, as fungi employ diverse means to adhere their spores to infection courts to begin the disease cycle. This adherence is required for infection to occur. As the primary means of fungal growth, hyphae are also incredibly important structures to understand. Hyphae require maintenance of polarized growth to properly extend the mycelium. Here, I investigated the role cytoskeletal proteins play in both spore adhesion and polarized hyphal growth using fluorescence microscopy. I found that conidial adhesion in C. graminicola is a polarized phenomenon in which an adhesive strip that localizes only to one face of the conidium is responsible for adhesion. This strip colocalizes with a polarized actin array that is present only in conidia detached from conidiophores. This discovery grants insight into the adhesion strategy of C. graminicola, as we hypothesize that the actin array plays a role in generation of this adhesive and that the polar nature of the strip grants conidia a dispersal benefit. Additionally, my research found that hyphal growth is strongly correlated with the localization of proteins associated with the endocytic collar. This correlation is strongest when determining the distance these proteins are behind the growing apex. Interestingly, the rate of endocytosis does not seem to correlate with the rate of hyphal growth, suggesting that it is the regulation of the location of endocytosis that plays the greatest role in growth rate, not the speed at which endocytosis occurs.