Fig. 5. Visualization of the cyst progression checkpoint. Acridine Orange staining (A,A',B,C) and TUNEL (E,E',F) identify apoptotic germline cells in region 2 of the germarium. Vital Acridine Orange staining of wild-type germaria in M3 medium is visible as green (A) or red (A') fluorescence; signal is localized to region 2 of the germarium. (B-C) In phosphate buffer, where Acridine Orange signal is amplified, da^lyh mutants (B) show dramatically reduced fluorescence relative to wild type (C). (B,C are shown at the same magnification; lines indicate the positions of the germaria for comparison.) (D) Apoptosis as measured by vital Acridine Orange staining of germaria from 2- to 4-day old adult wild-type and da mutant females. Blue numbers indicate total number of germaria scored; bars show the average percentage per female ±s.e.m. (n=11 for da⁷/da^s22, n=10 for all others). (E,E') TUNEL (green) labels cells at the region 2a/2b boundary; staining corresponds with decreased DAPI intensity (E''). (F,F') Reduced Vasa (magenta) identifies apoptotic cells as germline and corresponds with smaller punctate DAPI staining.