Fig. 3. Sec5 localization and the establishment of the anteroposterior axis. (A-D,I-K,M) Egg chambers, stage and genotype indicated, were stained with phalloidin (red), Hoechst (blue) and anti-Sec5 monoclonal 22A2 (green). (A,B) Sec5 concentrates posteriorly, at the boundary between the follicle cells and the oocyte. Particularly at stage 5, sec5 resides at the apical end of the two posterior polar cells (arrow in merged image). (C,D) Sec5 persists in the posterior follicle cells (arrows) when the germline is homozygous for sec5^E13. (E-H) Follicle cell clones of sec5^E13 (marked by the absence of GFP). (E,F) The oocyte is labeled with anti-Orb (also green), and membranes are marked with phalloidin (red). When the posterior follicle cells are homozygous for sec5^E13 (F; arrow), the oocyte (^*) no longer occupies the posterior-most position. (G) Two z sections through one egg chamber. Again, the sec5^E13 follicle cell clone at the posterior (arrows) causes the oocyte (^*), labeled with anti-Gurken (green), to reside too anteriorly. Adherens junctions between follicle cells are labeled with anti-E-cadherin (red). (H) In larger sec5^E13 follicle cell clones (arrowhead), the epithelium is disordered compared with heterozygous cells (arrow). (I-K) Wild type. At stages 6-8, Sec5 appears increasingly at the anterior of the oocyte (arrows). (L) A colcemid-treated stage 10 egg chamber wherein the oocyte nucleus (^*) did not migrate correctly. Sec5 (green) still concentrates at the anterior membranes of the oocyte. (M,N) At stage 10, Sec5 concentrates at the anterior corners (arrows), and is nearly absent from the posterior membrane. (O) Syntaxin (red) is uniformly localized on the oocyte membrane. The nucleus is marked with an asterisk. Scale bars: 20 µm.