Fig. 4

a Time-lapse fluorescence images of a H2B-mCherry tail explant in which the posterior end of the notochord is ablated using laser microsurgery. Ablated region is indicated with the orange dashed line (Noto: notochord, A/P: anterior/posterior, D/V: dorsal/ventral). b The elongation of the tail over time for the explant shown in (a). Grey shaded part indicates the period during which the elongation process is affected. Time passed from ablation until the start of the movie is indicated before t = 0 with dashed line (free explant N = 4, n = 13, Noto ablated explant N = 5, n = 10). c Somites formed next to the ablated notochord region (highlighted with the line in between asterisks) are malformed. White arrows indicate the somites. d Time-lapse fluorescence images of the ablated notochord region show the elongation of the notochord at the tip. Blue, purple and yellow arrows indicate the anterior and posterior ends of the ablated region and the posterior most end of the elongating notochord respectively. e (top) Schematic showing the right and left part of the tail explant that are ablated from the mediolateral and anteroposterior views (L/R: left/right, P: posterior). (bottom) Fluorescence images showing the ablated regions of both sides of the PSM. f Time-lapse fluorescence images of a tail explant where both sides of the posterior PSM are ablated. Orange dashed lines are to see the notochord easily. g Tail elongation curve of the explant shown in (f). Grey shaded part indicates the period during which the elongation process is affected. Time passed from ablation until the start of the movie is indicated before t = 0 with dashed line (free explant N = 4, n = 13, PSM ablated explant N = 5, n = 11). Scale bars, 100 μm.