Fig. 6. Stage-specific GAL4-USP activation by 20E in imaginal discs. Larval organs dissected from heat treated hs-GAL4-USP; UAS-nlacZ third instar larvae at 18 and 4 hours before puparium formation were cultured with 5x10^–7 M 20E (+20E) or without hormone (–20E). No GAL4-USP activation is seen in the absence of 20E (A,C). In the presence of 20E, GAL4-USP activation is observed in imaginal discs from mid-third instar larvae (B) but not in discs from late third instar larvae (D).