Fig. 5. Jak/Stat regulates dpp signalling in the GSC niche. (A) Germarium from a tub- Gal80^ts/UASt-hop^Tum; bab1-Gal4/+ female Drosophila stained with anti-Hts showing the extra GSC-like cells and blocked cyst differentiation produced by bab1-Gal4-driven overexpression of hop^Tum in adult germaria. (B) Detection by real-time PCR of the relative levels of dpp and gbb mRNAs in ovaries from tub-Gal80^ts/UASt-upd2; bab1-Gal4/+ females as compared with tub-Gal80^ts/+; bab1- Gal4/+ controls. On average, dpp mRNA levels increased 3.25-fold in experimental ovaries, whereas the amount of gbb mRNA did not vary substantially under the same experimental conditions. The black triangle denotes that the mean difference was statistically significant in the case of dpp mRNA but not in the case of gbb mRNA (Student's t-test, P<0.01; the mean values are averages of three different replicas from three independent experiments). (C-D''') Wild-type (C) and tub-Gal80^ts/UASt-upd2; bab1-Gal4/+ (D) germaria stained with anti-Hts (red), anti-pMad (a reporter of Dpp pathway activation, green) and the DNA dye TOPRO-3 (blue). The white dashed lines demarcate the areas magnified in C',C'' and D'-D'''. (C-C'') Wild-type germarium showing pMad protein restricted to the GSCs. (D-D''') A tub-Gal80^ts/UASt-upd2; bab1-Gal4/+ germarium showing expanded pMad staining within the ectopic GSC tumour. Asterisks, GSCs. Scale bars: 10 µm.