Expression pattern of different GAL4 driver lines. The GAL4 driver lines were tested for the expression of UAS-GFP. A) The e22c-GAL4 line drives GFP expression in the follicular stem cells and thus in all FCs, albeit patchy. B) Slbo-GAL4 expresses strongly in border cells, in stretched FCs and in columnar FCs at the dorsal anterior side (centripetal FCs) and the posterior end and also in posterior FCs at early stage 9. C) Fru-GAL4 drives expression in stalk cells, in anterior and posterior FCs from stage 6/7 on, in border cells, stretched FCs and in the very posterior columnar FCs. D) c355-GAL4 expresses from stage 7 onwards in all cells including border, stretched, and columnar cells, but not in polar cells. E) c306-GAL4 expresses in stalk cells, weakly in anterior- and stronger in posterior FCs, border cells, stretched cells and columnar FCs, similar to slbo-GAL4. F) 109-30-GAL4 drives expression in stalk precursor- and stalk cells. G) Upd-GAL4 expresses exclusively in the polar cells. H) Ey-GAL4 served as a control and does not drive expression in the ovaries. I) Summary of the expression patterns of the GAL4 lines used. J) Schematic drawing showing the position of all cell types specified above during different stages of oogenesis. Anterior/posterior FCs corresponds to the stages 6/7 to early 9, stretched and columnar to stages 9 till stage 10/11. Anterior is to the left, posterior to the right. Abbreviations: a, anterior; p, posterior; d, dorsal; v, ventral; s, stage. Scale bar: 50 μm. Genotypes: A: e22c-GAL4/UAS>GFP, B: slbo-GAL4/UAS>GFP, C: fru(168)-GAL4/UAS>GFP, D: c355-GAL4/+; UAS>GFP/+, E: c306-GAL4/+; UAS>GFP/+, F: 109-30-GAL4/UAS>GFP, G: upd-GAL4/+; UAS>GFP/+, H: ey-GAL4/UAS>GFP.