Fig. 7. Delta2/Notch signalling is required for secondary notochord induction. (A-C) The embryonic treatment is indicated above the panels and the marker analysed on the left. n=total number of embryos examined. (A) Expression of Ci-Bra at the early gastrula stage and Ci-Noto1 at the early tailbud stage following inhibition of Delta2/Notch signalling. The graphs show the percentage of embryos (y-axis) expressing Ci-Bra or Ci-Noto1 in one or two B8.6 blastomeres following the treatments indicated on the x-axis. (B) Ablation of A6.3 on the left-hand side (lA6.3) leads to a loss of Ci-Bra expression in the secondary notochord precursor on the ablated side. The schematic drawing of a vegetal pole view 32-cell stage embryo shows the A6.3 blastomere (dark pink) relative to the presumptive secondary notochord precursor (blue). The graph shows the percentage of embryos (y-axis) expressing strong or weak Ci-Bra in B8.6 on the left-(L) or right-(R) hand side of the embryo, following ablation of A6.3 on the left-hand side. (C) Expression of Ci-Twist-like 1 at the early gastrula stage following inhibition of Delta signalling. The DAPT-treated embryo shown is tilted slightly (far right) in order to show more clearly the B8.6 blastomere (arrowhead), which is not expressing Ci-Twist-like 1. The graph shows the percentage of embryos (y-axis) expressing Ci-Twist-like 1 in at least one cell of the different lineages following the treatment indicated on the x-axis.