dally regulates formation of the female GSC niche in the pupal ovary. (A) Early pupal ovary from a dally heterozygous female. Background staining with anti-Hts (red) outlines developing somatic cells in the anterior. PGCs are labeled by anti-Vas antibody (blue). More posteriorly, germ cells start to differentiate (bracket) and express Bam protein (detected by anti-Bam antibody; green). The fusome is stained with anti-Hts. (B and C) Two examples of dally homozygous early pupal ovaries stained with anti-Bam antibody. The most anterior PGCs (asterisks) express Bam protein (green). (D–F) bam expression was also examined using a bam-GFP reporter (green) in dally heterozygous (D) and homozygous (E and F) ovaries. Weak (E) and strong (F) bam-GFP signals were detected in the most anterior PGCs (asterisks). The bracket (D) indicates Bam-positive differentiating germ cells. (G) bam-GFP expression in a sfl mutant ovary. Premature expression of bam in the most anterior PGCs occurred in 20% and 86% of dally and sfl pupal ovaries, respectively. The asterisk indicates the most anterior PGCs. See also Fig. S1 C. (A–G) Arrows indicate the anterior edge of the germ cell population. Anterior is to the left. Bars, 10 µm.