Fig. 5. Overexpression of Delta alters follicle cell fates and antagonizes Unpaired signaling. (A-B') Dl overexpression using the A101-GAL4 polar cell-specific driver induces extra polar cells (green). Some of these extra cells express the main-body follicle cell marker Eya (arrow, red in A,A') or the stalk marker Bib (arrowhead, red in B,B'). (C,C') Dl overexpression using the Upd-GAL4 polar cell-specific driver results in loss of the stalk and fusions between neighboring cysts. Two confocal planes of three germline cysts from a single ovariole are shown. Fas3 (red) marks polar cells in the oldest egg chamber (designated #1, arrowhead). (D) Dl overexpression using the 24B-GAL4 stalk cell-specific driver induces the expression of the polar cell marker, neur^A101 (arrowhead, red).