Mechanical impedance of tip extension induces apical hyphal branching.

<p>(A) Representative example of branch induction following interaction with a single neutrophil. (i) Hyphal growth (green) through channels and interactions with neutrophils (blue), as observed in time-lapse microscopy (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006154#ppat.1006154.s003" target="_blank">S1 Movie</a>) (ii-iv) Magnified view of frames extracted from time-lapse microscopy of interactions (dashed red square box in i), which demonstrate formation of actively growing new hypha tips (full white arrowheads) following interaction with a single neutrophil (open white arrowhead), in addition to the primary tip (open green arrowhead). (B) Induction of branching during interaction of the hyphal tip with a crescent-shaped obstacle. (i) Hyphal growth (green) through channels with obstacles, as observed in time-lapse microscopy (<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006154#ppat.1006154.s006" target="_blank">S4 Movie</a>) (ii-iv) Magnified view of frames extracted from time-lapse microscopy (dashed red square box in i), show efficient formation of a new hypha tip (full white arrowhead) in addition to the primary tip (open green arrowhead). (C) Comparison of branch induction by differently shaped obstacles. Square and crescent shaped obstacles provided robust branch induction. (D) Comparison of average hyphal tip velocity during interaction period (-20 to +25 mins relative to contact with obstacle). Crescent-shaped obstacles slowed hyphal tip extension most efficiently during interaction. (E) Graphing of instantaneous hyphal tip velocity during interaction with differently shaped obstacles (i-iv). Crescent shaped obstacles induced a striking decrease in tip velocity during the interaction, just prior to branching (black arrow indicates steep drop in tip velocity). N ≥ 9 measurements per condition from n ≥ 7 representative hyphae per group. Errors bars: mean ± SEM. Statistics: One-way ANOVA with Tukey’s post test. Adjusted p values: *p≤0.05, **p≤0.01, ***p≤0.001, ****p≤0.0001.