Dioxin Toxicity In Vivo Results from an Increase in the Dioxin-Independent Transcriptional Activity of the Aryl Hydrocarbon Receptor
Figure 3
Ahr activity is enhanced by dioxin or addition of Arnt or extra Tgo.
(A) Leg phenotypes. Genotypes and presence of dioxin are indicated above the panels. The number of tarsal segments present is indicated. Arrows point to proximal leg deformities. (B) Late third instar leg imaginal discs showing Dac (green) and Bar (red) expression; genotypes as above. The normal (arrowheads) and ectopic (arrows) repression of Dac and Bar is indicated. (C) Late third larval-instar leg imaginal discs showing Dac and Bar expression in a wild-type and ss mutant. (D) Wild-type Ss expression in leg imaginal disc during third larval instar. Notice the correlation between ss expression and repression of Dac and Bar (arrowheads). (E) Quantification of legs according to the number of tarsal segments displayed. From left to right: w; rn-Gal4 ssabr/sssta (ss mutant), w; UAS-ss/+; rn-Gal4 ssabr/sssta (ss rescue), w; UAS-Ahr/+; rn-Gal4 ssabr/sssta (Ahr rescue) and w; UAS-Ahr/+; rn-Gal4 ssabr/sssta fed with dioxin (Ahr+dioxin rescue). Notice that presence of five tarsal segments (red column) indicates full rescue of the mutant phenotype. A minimum of 80 legs, from at least 20 flies, were observed per sample (see Table S1).