Fig. 4. Function of the rho enhancer also diverged between D. melanogaster and D. virilis. (A-I) D. melanogaster transgenic flies carrying both Dmel rho^2.2-ß-Gal (magenta in A,C,D,F,G,I) and Dvir rho^4.2-GFP (green in B,C,E,F,H,I) reporters were generated. The activities of the two enhancers were then determined at different developmental stages: early in stage 10B (A-C), late in stage 10B (D-F) and stage 12 (G-I). (A-C) At early stage 10B, Dmel rho^2.2-ß-Gal (A) was activated, but Dvir rho^4.2-GFP (B) was not yet active (C). (D-F) Late in stage 10B, Dvir rho^4.2-GFP expression began (E) in a pattern similar to that of Dmel rho^2.2-ß-Gal (D). The domain of Dvir rho^4.2-GFP activation (E) largely overlapped with that of Dmel rho^2.2-ß-Gal (D), although a slight posterior expansion of Dvir rho^4.2-GFP was seen (F). (G-I) The anterior boundaries of the Dmel rho^2.2-ß-Gal (G) and Dvir rho^4.2-GFP (H) activation domains were similar, but the posterior expansion of Dvir rho^4.2-GFP expression became prominent (I). The right panels are merged images of the left and middle panels.