Fig. 2. The effect of da on polar and stalk cell markers. (A) Enhancer trap B1-93F marks interfollicular stalks, presumptive stalk cells and terminal filament in wild type. In da⁷/da^s22 (B) and da^lyh (C) ovaries the enhancer trap stains clusters of cells that are sometimes arranged into rope-like patterns. Expression of B1-93F is weaker in da mutants (C, arrowheads) relative to the overexposed terminal filament (C, asterisk). This enhancer trap is also expressed in degrading somatic cells often present at the posterior of da mutant ovarioles (B, asterisk). (D) In wild type, enhancer trap A101 stains polar cells in each follicle; initial expression may include up to 4 cells at either pole (3 shown in inset), but by stage 4 staining is limited to 2 cells at each pole. (E) In da⁷/da^s22 mutant ovaries, clusters of 3 or 4 somatic cells are found throughout ovarioles, apparently corresponding to ends of each cyst in a compound follicle. (F) In more severely disrupted da mutant ovarioles, a large number of A101-positive cells are found throughout a region that is anterior to extensive degradation. (G) In wild type, FasIII protein is found initially in all somatic cells in regions 2b and 3 of the germarium; levels subsequently diminish in all but the polar cells. (H-I) In da mutants, clusters of 3 or 4 FasIII-positive cells are found along compound follicles, corresponding to cyst poles.