Fig. 6. Twist can activate vnd and sim without Dorsal. Embryos were stained with twist (A,B), sim (C), and vnd (D-F) RNA probes, and are oriented with anterior to the left and dorsal up. (A,B) Mutant embryos were obtained from gd^–/gd^– females and completely lack Dorsal nuclear protein. There is no twist expression in these mutants (A), but twist exhibits intense expression in anterior regions of mutant embryos that contain the twist-bcd transgene (B). (C,D) sim (C) and vnd (D) staining patterns in gd^–/gd^– mutant embryos that contain the twist-bcd transgene. Staining is detected in anterior regions where there are high levels of Twist. (E,F) The vnd expression pattern in precellular (E) and cellularized (F) wild-type embryos that contain the twist-bcd transgene. vnd expression is induced at the anterior pole in early embryos by the twist-bcd transgene (E), but this anterior expression is lost during the onset of the endogenous expression pattern (ventral stripes) after cellularization (F).