Fig. 2. The subapical MT band is required for the formation of a mechanical frame to maintain the shape of the zygote tip.
(a–l) Dynamics of untreated zygote (a–d) and zygotes treated with an MT polymerization inhibitor (1 μM oryzalin) (e–h) or a depolymerization inhibitor (10 μM taxol) (i–l). a, e, i Time-lapse images. b, f, j Contour dynamics up to just after cell division (11:20; b and 15:00; j) or nuclear condensation (14:20) (f). c, g, k Time course of cell growth rate (dL/dt; red) and tip radius (re; blue). d, h, l Kymographs showing MT and nuclear signal intensities. No MT band was detected in oryzalin-treated zygotes due to diffused signals (Supplementary Movie 2). Dashed black lines in (d, l) indicate the upper and lower ends of the MT band; its precise area could not be extracted by Gaussian fitting in (l) due to the distorted shape of the signal peak (Supplementary Movie 3). Yellow arrows mark the timing of cell division in (d, l). m Boxplot showing the ratio of apical to basal cell length, as an indicator of zygote division asymmetry. Center line, median; box limits, upper and lower quartiles; whiskers, maximum and minimum points within 1.5 × the interquartile range from box limits. Individual data points are also shown. Significant difference was detected by two-sided Welch’s t-test (**P = 0.00631; n = 14 and 12 for untreated (none) and taxol-treated ovules, respectively). Images are representative of 14, 16, and 12 samples for untreated (none), oryzalin-treated, and taxol-treated samples, respectively. Scale bars: 10 μm. Source data are provided as a Source Data file.