Fig. 2. Ectopic germline expression of Stwl induced an expansion of germline stem cells. (A) Germarium from Nos-Gal4 control animals contained a dividing stem cell that can be recognized by the elongated fusome (arrow) connecting the germline stem cell (GSC)-cystoblast pair of cells that were negative for bam-GFP (red, anti-Hts; blue, Hoechst; green, GFP). (B) Projection of three confocal sections from Nos-Gal4>stwl^EY animals. Arrow shows GSC-like cells. (C) Graph showing the average number of GSCs/germarium in various genotypes: Nos-Gal4 alone (light purple), Nos-Gal4 driving CG3919 (a gene neighboring stwl, blue), Nos-Gal4 driving stwl (green), Nos-Gal4 driving stwl/nos^RC (pink), Nos-Gal4 driving stwl/Df(nos) (dark purple) or Nos-Gal4 driving stwl/pum^ET9 (yellow). bam-GFP-negative cells containing single, spherical fusomes were scored as GSCs (Xie and Spradling, 1998; Chen and McKearin, 2003a). The difference in the number of GSC-like cells in Nos-Gal4>stwl^EY (Nos->Stwl in C) ovaries was statistically significant by unpaired t-test (P<0.001) when compared individually to the number of GSC-like cells scored in the other genotypes presented in C.