Fig. 2. Localization of a wing-specific regulatory element of knot. (A) Genomic region upstream of the knot gene. The first exon of knot is shown in blue. Exons of neighboring genes are shown in gray. Regions 10-15 kb upstream of the transcription start site were tested for cis-regulatory activity. Regions directing expression in the wing are indicated in blue and regions lacking activity are indicated in black. (B) VISTA plot (Couronne et al., 2003) of kn^Mel1-2330 fragment aligned with sequence from D. pseudoobscura and D. virilis. A window size of 50 bp was used, and regions that are greater than 70% identical are indicated in orange. Shown below are the constructs generated on the basis of the distribution of sequence conservation among Drosophila. (C) lacZ reporter expression in the wing imaginal disc under the control of the kn^Mel701-1991 fragment. No expression is observed in the haltere imaginal disc (inset). (D) Wing imaginal disc of individual carrying kn^Mel701-1991 fragment stained for Knot protein (red) and lacZ (green). The yellow stripe indicates complete overlap of the two patterns.