Fig. 3. Proneural gene expression is reduced when Dpp signaling is impeded. Expression of the proneural gene products, Ato (green) and Ac (red), in PNCs and SOPs at stage 11 (A-H). (A,B) The number and position of serially homologous PNCs and SOPs are similar in A1-A7 wild-type abdominal segments. (C-H) Proneural gene expression is lost in some segments in shn^k04412 homozygous embryos (C,D), embryos expressing HS-ssog (E,F) and embryos overexpressing brk in segments A1-A3 (G,H). Arrows point to SOPs and PNCs that are not present in certain other segments. (I) Visualization of apoptotic cell death with Acridine Orange reveals no preferential cell death in segments A1-A3 versus other abdominal segments in embryos overexpressing UAS-brk under Kr-Gal4. (J,K) Active TGFß signaling is visualized by anti-p-Mad antibody at stage 9 embryos (Tanimoto et al., 2000). While WT embryos show a broad expression domain of p-Mad (J), embryos where ssog is expressed under heatshock show a severe reduction in p-Mad levels and expression domain (K). The effect varies among embryos: some embryos have no p-Mad after the heat shock treatment.

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