Figure 3.

Enhancer activity of D. melanogaster yellow fragments. Below the schematic of overlapping sequence regions from the 5′ intergenic and intronic regions of the D. melanogaster yellow gene tested for enhancer activity are images of transgenic pupae, which show expression from the GFP reporter genes in magenta. Expression driven by fragments from the 5′ intergenic region (A and B) and the intron (C and D) is shown in the body (A and C) and wings (B and D), for both female (top row) and male (bottom row) flies. Summary tables below each pair of pupal bodies (A and C) and wings (B and D) show our interpretation of these images: “++” indicates strong fluorescence observed in the body region, whereas “+” indicates weaker fluorescence. Blue arrows highlight elevated expression in a region of the wing driven by the mel_A1 fragment, and expression in the margin bristles driven by the full D. melanogaster intron (“Full mel_int”) and the mel_A6 fragment. The asterisk next to the mel_A5 fragment indicates that activity of this element is shown for flies heterozygous for the reporter gene. All other images show GFP expression in flies homozygous for the reporter gene. The magenta color used in this figure makes it easier to see low expression levels; a copy of this figure with GFP expression shown in the more traditional green is provided as Figure S2. The dimorphic expression driven by mel_A6 and the wing blade expression driven by mel_A4 were equivocal, and went through a secondary inspection before reaching a consensus among authors.