Fig. 3. p38 is required for oral specification at late blastula stage. (A) Schematic depicting the experiment in B. Corresponding hours post-fertilization (h) are indicated. (B) Embryos were treated with SB at the indicated stages (B1-B4), and then cultured to the pluteus stage. Morphological (top) and skeletal (bottom, illuminated with plane-polarized light) images are shown. (C-E) Whole-mount in situ analysis for Nodal (C), Gsc (D) and Tbx2/3 (E) in embryos treated with SB at 5 (1), 6 (2,3) and 7 (4) hpf. Vegetal views at late gastrula stage are shown. EB, early blastula; HB, hatched blastula; TVP, thickened vegetal plate; MB, mesenchyme blastula; Plut, pluteus larvae.