FIGURE 2

Reporter genes are used to ascertain enhancer activity. (a) A schematic of the D. melanogaster yellow gene is shown, containing two exons, a basal promoter, and multiple tissue-specific enhancers. (b) Reporter genes contain enhancer sequences, a generic basal promoter, and coding sequences for an easily visualized protein, such as the Green Fluorescent Protein (GFP) or -galactosidase (-gal). The composition of a GFP reporter gene for the D. subobscura 'body' enhancer is illustrated. (c) When transformed into a fly, the reporter gene provides a read-out of enhancer activity. GFP expression driven by the D. subobscura body enhancer at a late pupal stage is shown in a D. melanogaster transformant fly on the right, with a wild type fly on the left. Note that reporter gene expression within each abdominal segment (bracket) is comparable to expression of the endogenous D. subobscura Yellow protein shown in Figure 1e. (Expression in eyes and ocelli is due to Pax6-GFP transformation marker, not the D. subobscura body enhancer.)