ATK depletion reduces branching MT migration. (A) Branching MT migration observed in the quadruple KCBP KO line. Red and white arrowheads indicate MT branching points and migrating MT, respectively. Bar, 2 µm. (B) Poleward movement of citrine-ATK-a signals in the phragmoplast. Image sequences and kymographs are shown. Bars: (top) 5 µm; (bottom left) 1 µm; (kymograph) 10 µm/2 s. (C) Velocity of citrine-ATK-a motility in the phragmoplast (n = 30). (D) Citrine-ATK-a signal detected at the migrating branch points (arrowheads). Bar, 2 µm. (E) Frequency of citrine-ATK-a localization at the migrating or nonmigrating branching point. (F) Frequency of branching MT migration (per branching nucleation, ± standard error; n = 2 [control ATKbΔ] or 3 [ATK-a/-IbΔ RNAi] experiments). 21–37 branching MTs were identified in three cells for each experiment.