Figure 2. Gene expression in wingless null mutant patches surrounded by wild type or NRT-Wingless-expressing cells.

a-c, Expression of Distalless (Dll) and Wingless (Wg), as detected by immunofluorescence, in ‘null-in-wt’ (a) or ‘null-in-NRT’ (b, c) clones. Null wingless mutant territory (wg^CX4) is marked by the absence of GFP. Red arrows indicate shortrange activation of distalless expression by NRT-Wingless. Turquoise arrowhead highlights longer range of wild type Wingless. Pink arrowhead and yellow asterisk indicate persistent expression (memory) in zones 2 and 3 respectively. d, Diagram showing regions where the behavior of null mutant clones was analyzed. Region 1 links the prospective wing to the prospective hinge. Region 2 represents the domain straddling the D-V boundary that expresses high level Distalless. Region 3 represents the prospective wing blade, which expresses graded, low level Distalless. Disparities in disc size between panels b and c are due to staging differences.