Septin abundance scales with positive curvature in A. gossypii. (A) Septin higher-order structures in A. gossypii, visualized by Cdc11a-GFP using structured illumination microscopy (SIM). Straight bundles (1), thin filaments (2,) and branch assemblies (3) exist in the same cell. (B) SIM images of Cdc11a-GFP signal at the base of four lateral branches emanating from hyphae at distinct angles, producing different curvatures. (C) Mean curvature heat map produced by imaging Blankophor in the A. gossypii cell wall followed by curvature analysis. For this display, curvature was mapped onto the external surface and values were inverted to represent curvature as viewed from the cell interior. (D) Cdc11a-GFP intensity at the base of branches plotted against positive and negative principal curvatures and mean curvature as viewed from the cell interior. Diagrams illustrate the curvature measured in each plot. (E) Filament orientation at the base of branches visualized by Cdc11a-GFP SIM. (F) Filament orientation in hyphae, away from sites containing a positive curvature component. (G) Filament orientation relative to the hyphal axis was measured compared with a random simulation of filament orientations (solid lines, mean; dotted line, SD; n = 263 filaments in 13 hyphae). (H) Colocalization of Cdc11-mCherry (green) and Hsl7-GFP (magenta) at the base of branches and straight bundles in A. gossypii.