Figure 3.

Schematic representation of transgenes and their expression response in btd mutant embryos. Transgene constructs (Left) and rescue response of transgene-bearing btd mutant embryos are shown as assayed by Engrailed expression, the presence of sensory neurons in the head region, and cuticular head markers (ref. 28; for details, see Fig. 4). btd>btd and btd>Sp1 rescue is shown for comparison (5, 17). ++, a full rescue of btd mutant embryos [i.e., the corresponding set of segment markers could be scored in transgene-bearing btd mutant embryos (n ≥ 50 embryos analyzed)]; +, a partial rescue (i.e., only a subset of segment markers was found); −, no rescue. Representative examples of rescued embryos are shown in Fig. 4.