Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSCharacterisation of contact-dependant tip re-orientation in Candida albicans hyphae. Darren Thomson, Silvia Wehmeier, Alex Brand. Aberdeen FungalGroup, Aberdeen University, Aberdeen, United Kingdom.Candida albicans is a pleiomorphic fungus that lives as a commensal yeast in the human body but can become pathogenic in susceptible patient groups.Virulence is strongly linked with the production of penetrative hyphae that can adhere to and invade a wide range of substrates, including blood vessels,organ tissue, keratinised finger-nails and even soft medical plastics. Using live-cell imaging and nanofabricated surfaces, we are characterising the spatiotemporaldynamics of contact-induced hyphal tip behaviour (thigmotropism). To test whether tip re-orientation responses positively correlate with levelsof hyphal adhesion, we generated substrates with increasing adhesive force. Hyphal tip re-orientation was absent in poorly-immobilised hyphae and athreshold adhesive force was required sub-apically to generate the hyphal tip pressure required for re-orientation. Interestingly, sub-threshold adhesionresulted in sub-apical hyphal bending. Localization of fluorescent protein markers for the Spitzenkörper and the Polarisome (Mlc1-YFP and Spa2-YFP,respectively) showed that C. albicans hyphal tips grow in an asymmetric, ‘nose-down’ manner on a surface. Additionally, hyphal tips can detect surfacestiffness and show a distinct preference for nose-down growth on the softer of two substrates. Localisation of fluorescent cell-cycle reporter proteins overtime revealed that hyphal tip contact slowed the cell-cycle, suggesting that tip-contact perturbs cell-cycle mechanics. Finally, we examined the role ofcytoskeleton regulators in thigmotropism and determined the force that can be generated by the hyphal tip. Our results suggest that C. albicans hyphaecan exert sufficient force to penetrate human epithelial tissue without the need for secreted enzyme activity. This is consistent with the observed hyphalpenetration of medical-grade silicone, which has a similar Young’s modulus to human cartilage.102