Figure 2.

Contribution of Vein to patterning the ventral ectoderm. (A) In embryos heterozygous for the spitz^OE92 null mutation, expression of FasIII is identical to the wild-type pattern, namely in four to five cell rows on each side of the midline. (B) In embryos heterozygous for spitz, which are also homozygous for a null heteroallelic combination of vein, expression of FasIII in the cell row adjacent to the midline is normal, but is not observed in more lateral rows. (C) In rho^Δ38 mutant embryos expression of FasIII in the ventral ectoderm is eliminated, and only some expression in the neuroblast layer is retained. (D) Induction of ubiquitous Vein expression in rho mutant embryos by 69B–Gal4 restores the normal expression pattern of FasIII. Arrows mark the ventral midline. Note: In vein homozygous mutant embryos, FasIII expression is normal, as in spitz heterozygous embryos, even when embryos are raised at conditions which may be stressful, such as 29°C.