Fig. 2. A 348 bp fragment contains a core module for ato activation in eye progenitors. (A) Schematic showing the DNA fragments driving reporter gene expression in the different constructs. The green bars IC1, IC2, A1 and A2 mark the relative positions of the evolutionarily conserved DNA sequences investigated in this work. (B-F') All panels (except D',E',F') show in situ hybridization to LacZ mRNA. Staining times differ and were optimized for visualization of either the entire stripe (large panels) or the initial clusters (small panels). For a summary of relative levels of expression for all constructs see Fig. S1 in the supplementary material. Panels D',E',F' show confocal images of triple stainings for the Sens (green), ß-gal (blue), and Eya (red) proteins. (B) Early phase of ato expression as reported by 3'ato^M"- ßgal. (C) Loss of eye disc expression in 3'ato^M"-348-ßgal. A faint signal could be detected along the margins of the eye disc after overnight ß-gal staining (not shown). (D-D') 3'ato^1.2- ßgal is sufficient to drive high level reporter gene expression in the early ato pattern including the initial clusters (D,D'). The anterior margin of ß-gal protein expression (blue) lies anterior to Sens (green) but posterior to the anterior margin of the Eya domain (red) (D'). (E-E') 3'ato³⁴⁸- ßgal drives reporter gene expression in a stripe (E). However, the initial clusters do not form (E'). Activation of the reporter gene (blue) occurs in more anterior progenitors as shown by the shift of the anterior margin of ß-gal protein expression (blue) farther away from Sens (green) and closer to the anterior border of the Eya domain (red) (E'). (F-F') 3'ato^1.2-298- ßgal drives reporter gene expression in a stripe (F). However, the initial clusters do not form (F'). The anterior margin of ß-gal protein expression (blue) appears to be minimally affected (F').