Figure 1. The svb cis-regulatory region in D. melanogaster.

a, Drawing from the lateral perspective of a D. melanogaster first instar larva. The domain producing quaternary trichomes on the fifth abdominal segment is enclosed in a red outline. b, Diagram of the region upstream of the svb first exon, showing the positions of the five enhancers for this locus: DG2, Z, A, E, and 7. The expression driven by these enhancers in quaternary cells is shown in purple in the diagrams below each enhancer. The piggyBac elements used to generate Df(X)svb¹⁰⁸ are shown as blue triangles. c,f, Expression pattern driven by D. melanogaster Z::lacZ (c) and DG2::lacZ (f) in the 5th and 6th abdominal segments of a stage-15 embryo (purple). An anti-Dusky-like antibody was used to stain developing trichomes (green). d,g, Expression pattern driven by D. simulans Z::lacZ (d) and DG2::lacZ (g). e,h, Expression pattern driven by D. sechellia Z::lacZ (e) and DG2::lacZ (h). β-galactosidase protein produced by D. melanogaster Z::lacZ is expressed in the cytoplasm; β-galactosidase from all other constructs is localized to the nucleus.