Fig. 1. High resolution detection of mitochondria. (A) The germarium in cross-section; at the anterior tip (region 1, left) reside two germline stem cells (blue) as well as cystoblasts and growing cysts (gray). Region 2a contains 16-cell germline cysts that enter meiosis and begin centrosome migration, while in region 2b, more mature cysts associate with follicle cells (green), and stretch to span the entire width of the germarium. Subsequently, in region 3, a new follicle with a well-defined oocyte (white) prepares to bud off. The fusome (red) grows, branches and eventually breaks down, leaving a remnant in the oocyte; it provides a distinctive marker for each stage. (B) A transmission electron micrograph showing the nucleus (nu) and mitochondria (m) of a region 1 cystocyte. The inset shows a cross-section of a ring canal containing a fusome plug surrounded by mitochondria. (C) Another region 1 cystocyte sectioned facing a ring canal (arrowhead): mitochondria (anti-ATP synthase) are green, the fusome (1B1 antibody) is blue and ring canal actin (rhodamine phalloidin) is red. (D,E) Mitochondria within living 16-cell cystocytes (broken circles) are labeled with the mito-GFP fusion gene (D) or using Mitotracker (E). Scale bars: in E, 1 µm for B-E; 100 nm in inset in B.