Dpp and EGFr activity in C. capitata and D. melanogaster oogenesis. Posterior is to the right, ventral to the bottom. (A to B’) The grk transcript localizes in the dorsal-anterior corner of the oocyte, both in D. melanogaster(A,A’) and C. capitata(B,B’). A and B are stage 8; A’ and B’ are stage 10B. (C to D’) Expression of dpp differs between the two species: (C)D. melanogaster dpp expression starts in a subset of anterior follicle cells at stage 8 (arrowhead). (C’) At stage 10A dpp is only seen in a ring of follicle cells at the border between the nurse cells and oocyte (arrowhead). (D) In a stage 8 C. capitata egg chamber, the dpp transcript is seen in the border cell cluster (empty arrowhead), the nurse cells, and localized anteriorly in the oocyte (black arrowhead). (D’) At stage 10, the transcript localizes in a ring at the anterior-outer edge of the oocyte (arrowhead), see also (I). (E to F’) Expression of thickveins in all follicle cells of stage 9 (E,F) and early stage 10 (E’,F’) egg chambers of both species. (G to H) In both D. melanogaster(G) and C. capitata(H) stage 10A egg chambers, activation of the Dpp pathway, visualized with immunohistochemistry against pMad, occurs in the stretched follicle cells overlying the nurse cells, and a few anterior rows of columnar follicle cells. (I,I’) FISH of dpp in C. capitata. (I) In a stage 10A egg chamber the dpp transcript localizes just underneath the follicle cells (arrowhead; dashed line indicates border of follicle cells). (I’) In stage 11 expression can be seen in migrated follicle cells between the nurse cells and oocyte (arrowhead).