Fig. 4

Fig. 4 The NCEZ is specified by high levels of Bmp activity. (A) In WT, the NCEZ comprises 20–30° of the ventral margin. (B) The dorsally expanded Bmp activity in moderately ventralized din mutants leads to an enlargement of the NCEZ to a 60–70° arc of the ventral margin. (C) Further dorsal expansion of Bmp activity in boz din double mutants results in a dramatic NCEZ enlargement. Shown is a vegetal view of a boz din embryo, with a broken line marking the enlarged vegetal papc expression domain. Labeled cells moved into this vegetal region without translocating dorsally away from their original point of labeling. Furthermore, they fail to extend beyond the papc expression domain. (D) Cells from at least a 180° arc of the ventral margin constitute NCEZ in boz din mutants. (E) Dorsal view of a host embryo at the end of the gastrula period with transplanted cells (in brown) from a nonventralized host. At the beginning of gastrulation, the transplanted cells were in the ventral lateral region of the margin. (F) Cells that were transplanted from a strongly ventralized donor to the same ventral lateral region of the gastrula have moved into the tailbud region, shown in this vegetal view. (G) Dorsal view of cells transplanted from a nonventralized donor near the dorsal shield at the beginning of the gastrula period. They form arrays extending outside of the papc expression domain. (H) Dorsovegetal view of a host embryo with cells from a ventralized donor that were transplanted near the dorsal shield and have now moved into the posterior trunk and tailbud region.