MT plus ends follow trajectories that coalign with septin filaments. (A) MDCK cells expressing EB1-dsRed and SEPT2-YFP. The inset shows EB1-dsRed comets that localize on a perinuclear SEPT2-YFP filament in high magnification. (B) Kymograph depicts the movement of EB1-dsRed along SEPT2-YFP. (C) FRAP of α-tubulin (α-tub)–GFP in MTs coated with SEPT2-mCherry. The dashed line demarcates the region of FRAP. Arrows point to MT tips. Arrowheads mark the position of SEPT2-mCherry. (D and E) Time-lapse images show docking and coalignment of an MT tip (arrows) with MTs coated with SEPT2-mCherry. Line graph shows the fluorescence intensity of α-tubulin–GFP at sites of MT–MT docking (yellow arrowheads) and alignment (green arrowheads) and at a point of no MT overlap (blue arrowheads). Note that α-tubulin–GFP intensity increases at points of MT overlap. (F) Spinning-disk confocal microscopy images of EB1-dsRed and SEPT2-YFP. Still frames and time-composite images are depicted in the top and bottom rows, respectively. AU, arbitrary unit.