Fig. 7. gsc is able to act in vegetal blastomeres, while Xnot acts exclusively in the marginal zone. (A) Experimental scheme. tBR RNA was injected into ventral blastomeres of four-cell embryos. When embryos reached the 32-cell stage, gsc or Xnot RNA was injected into B4, C4 or D4 blastomeres together with lacZ RNA. (B-G) Cleared tailbud-stage embryos, injected with the indicated combination of factors/blastomeres, and showing the position of the X-gal staining (blue) and of the immunoreactivity for MZ15 (red).