Differential gene expression along the animal-vegetal axis in the ascidian embryo is maintained by a dual functional protein Foxd
Fig 4
Ectopic expression of animal hemisphere genes in the vegetal hemisphere of Foxd morphant embryos at the 32-cell stage.
(A) Illustrations of the 32-cell embryo. Blastomere names are indicated in the left half of the bilaterally symmetrical embryo. (B–I) The expression of (B, C) Prdm1-r.a (Bz1), (D, E) Prdm1-r.b (Bz2) (F, G) Dmrt1, and (H, I) Otx in (B, D, F, H) control unperturbed embryos, and (C, E, G, I) Foxd morphant embryos. Black arrows in (B, D, F, H) indicate expression in normal embryos, while magenta arrows in (C, E, G, I) indicate ectopic expression in Foxd morphant embryos. The number of morphant embryos examined and the proportion of embryos that each panel represents are shown below the panels. Scale bar, 100 μm. Note that Fgf9/16/20 is activated independently of Foxd at the 16-cell and 32-cell stages (S1D and S1E Fig; Fig 2A) [14–17], although it is later activated by Foxd (Fig 2B) [19]. Therefore, it is not strange that Otx expression in the animal hemisphere, which is under control of Fgf9/16/20 [11, 20, 21, 45, 46], was not affected at the 32-cell stage.