Fig. 2. Increasing spätzle dose expands the Twist domain. Young cellularized embryos were stained for Twist protein. Panels show cross-sections of embryos at 50% egg length. (A,B) In wild-type embryos (A), Twist is expressed in the ventral 20% of the embryo. In embryos laid by spz^- females that were injected with high levels of spz RNA (B), Twist expression is expanded to the ventral 40% of the embryo. (C,D) In embryos produced by Egfr¹ females (C), Twist is expressed in the ventral 50% of the embryo. In embryos laid by Egfr¹; spz^- females that were injected with high levels of spz RNA (D), Twist expression is expanded to the ventral 70% of the embryo.