Fig. 5. Gbb signaling is essential for repressing bam transcription in GSCs in the Drosophila testis. The testes in A-C are labeled for GFP (green), Hts (red) and DNA (blue); the testis in D is labeled for lacZ (red), GFP (green), Hts (white) and DNA (blue); the testes in E and F are labeled for Hts (green) and DAPI (blue). The hub cells are highlighted by circles, whereas some GSCs are highlighted by broken lines. (A) The tip of a bam-GFP wild-type testis showing no bam expression in GSCs (arrowhead) and gonialblasts (arrow). (B) The tip of a gbb⁴/gbb^D20 mutant testis (after being cultured at 29°C for one week) showing elevated bam-GFP expression in GSCs. (C) The tip of a punt¹⁰⁴⁶⁰/punt¹³⁵ mutant testis (after being cultured at 29°C for a week) showing elevated bam-GFP expression in GSCs. (D) The tip of a testis carrying a marked Med mutant GSC (arrowhead, lacZ negative) and unmarked wild-type GSCs (arrow, lacZ positive), showing elevated bam-GFP expression in the mutant Med GSC. (E) The tip of a hs-bam testis showing three remaining GSCs 1 week after heat-shock treatments. (F) The tip of a nos-gal4VP16;UAS-bam testis showing no GSCs. All the images are shown at the same magnification. Scale bar: 10 µm.