Figure 3.

Stage 12 embryos stained for FasIII (A–C) and Eve (D), compare with Fig. 1 B and E for wild-type patterns. (A and B) Induction of full-length bap in homozygous bap mutant background (Hsbap,Df(3R)e^D7,P[tin-CasPeRe28]; see ref. 2). Without heat shock no visceral mesoderm forms (A, asterisks), which is typical of bap mutants. In contrast, heat shock at 3.5–4.5 hr of development (stage 9) restores visceral mesoderm marker considerably (B, arrowheads). (C and D) Induction of full-length bap (same transformant as in A and B) in homozygous tin mutant background (Hsbap,tin^EC40) with a heat shock at stage 9 does not restore marker gene expression for either visceral mesoderm (C) or cardiac progenitors (D). The same results were obtained with other transgene insertions or when two heat shocks were applied. Tissue in situ hybridization after heat shock with a bap antisense RNA probe shows high and ubiquitous levels of bap expression (data not shown).