Fig. 6. Mild overactivation of the Dpp pathway mimics slmb mutant phenotypes. (A) Eggs laid by females bearing the weak Hs-gal4 driver and the strong UAS-dpp element that were subjected to heat shock show a dramatic expansion of the operculum (marked by arrowheads) and lack of DA. (B) DAPI staining of an ovariole dissected from one of these females reveals that many germ cells are surrounded by a single follicular epithelium. (C,D) Upon milder overexpression using the weak UAS-dpp element and the weak Hs-gal4 driver, ventralized eggshells with a single DA occurred. (E,F) Variable chorion phenotypes resulting from overexpression with the same UAS-dpp element driven by e22C-gal4: DA can be ramified (E, arrow), expanded (F) or greatly reduced (G). DA reduction was also observed upon overexpression of Medea with the weak Hs-gal4 driver (H) and in eggs laid by heterozygous sog^U2 females (I). Mild overexpression of Dpp with the weak Hs-gal4 or e22C-gal4 drivers (J-M) produced germaria with abnormal morphology (J), egg chambers with extra germ cells (K, arrow), mispositioned oocytes (L, arrow) and ovarioles lacking interfollicular stalks (M, arrowheads).