Contact‐induced apical asymmetry drives the thigmotropic responses of C andida albicans hyphae

Summary Filamentous hyphae of the human pathogen, C andida albicans , invade mucosal layers and medical silicones. In vitro , hyphal tips reorient thigmotropically on contact with small obstacles. It is not known how surface topography is sensed but hyphae lacking the cortical marker, R sr1/ B ud1, are unresponsive. We show that, on surfaces, the morphology of hyphal tips and the position of internal polarity protein complexes are asymmetrically skewed towards the substratum and biased towards the softer of two surfaces. In nano‐fabricated chambers, the S pitzenkörper ( S pk) responded to touch by translocating across the apex towards the point of contact, where its stable maintenance correlated with contour‐following growth. In the rsr1 Δ mutant, the position of the S pk meandered and these responses were attenuated. Perpendicular collision caused lateral S pk oscillation within the tip until after establishment of a new growth axis, suggesting S pk position does not predict the direction of growth in C . albicans . Acute tip reorientation occurred only in cells where forward growth was countered by hyphal friction sufficient to generate a tip force of ∼ 8.7 μN (1.2 MPa), more than that required to penetrate host cell membranes. These findings suggest mechanisms through which the organization of hyphal tip growth in C . albicans facilitates the probing, penetration and invasion of host tissue.