Fig. 3. pum mutant germ cells require zpg for differentiation. Ovaries from flies of the indicated genotypes were stained with anti-Vasa (green) and the mAb 1B1 antibody (red). pum mutant ovarioles were either devoid of germ line (B), or had a few defective, but differentiated, egg chambers and an empty germarium (A). zpg, pum double-mutant ovaries resembled zpg ovaries, with only a few germ cells at the tip of the ovariole, except that a few more germ cells were present. More cysts and egg chambers were also observed (D, arrow). Scale bar: in A, 20 µm; in B, 50 µm for B-D.