Fig. 4: Conservation of the morphological developmental transition at the tip in rat-SFB.

a−d Rat-SFB morphological stages equivalent to those identified at the tip of mouse-SFB. a/b/d(i) Representative tomographic slices from reconstructed tomograms showing SFB tip of stages: 1 (EMD-52695), 3 (EMD-52688) and 5 (EMD-52699). c(i) Representative projection images of the SFB tip of stage 4. The selected SFB from stages 1, 3, 4, and 5 have a length of 2.2, 3.0, 41.7 and 34.9 µm, respectively. a−d(ii) Segmentation rendering of rat-SFB tip from stages 1, 3, 4, and 5. The color legend is displayed at the bottom of the figure. The coloring of the hair-like structures (HLS) denotes their qualitative appearance. a−d(iii) Close-ups of the SFB tip. a−d(iv) Schematics of the SFB tip. Representative projection images of the distal end of rat-SFB in which a hair-like layer (HLL) was e absent and f present. SL Surface layer (S-layer); HLL hair-like layer; HLS hair-like structures; CW cell wall (composed of inner and outer wall zone); M membrane; C cytoplasm. g Length of SFB assigned to each tip stage (n = 32) obtained from 5 independent experiments. Individual measurements were plotted, the mean is shown and the statistical significance was assessed using the Kruskal–Wallis test followed by a Dunn’s test correction for multiple comparisons (stage 1 vs 5, p = 0.0023). Source data are provided as a Source Data file. Scale bars: a−d(i,ii): 50 nm; a−d(iii), e, f: 20 nm.