Fig. 3. Fusome-dependent formation of a Balbiani body. (A-D) Green, mitochondria (ATPsynthase); red, fusome (1B1). (A) Mitochondria in a 16-cell cyst (broken outline) midway in region 2a begin to associate with the fusome (red); in an older adjacent cyst (not outlined), they move toward the center of the fusome (yellow). (B) Mitochondrial movement along the fusome has progressed further in these two region 2b cysts (broken outline). (C) In cysts just entering region 3, clouds of mitochondria (arrowhead) accumulate near the ring canals that connect to the oocyte (small broken circle). (D) In region 3 follicles and young budded egg chambers, a Balbiani body containing many aggregated mitochondria (arrow) is visible in the anterior of the oocyte (small broken circle). (E) Electron micrograph of a region 3 follicle (large outline) reveals mitochondria entering the oocyte (small outline) via a ring canal (arrowheads) to form the Balbiani body (arrow). (F,G) Balbiani bodies fail to form in cysts from hts mutant females that lack fusomes. Arrowheads show mitochondrial clusters around presumptive centrosomes in the stem cells. Green, mitochondria (ATPsynthase); red, germ cells (Vasa); blue, DNA. (G) A stage 1 hts cyst (broken outline) showing the absence of a Balbiani body or mitochondrial clusters near presumptive ring canals. (H) Cysts mutant for egalitarian (egl) contain a normal fusome (red) but mitochondrial aggregates (green) of reduced size arise in all 16 cells at stage 1. Green, mitochondria (ATPsynthase); red, fusome (1B1). Scale bars: in H, 10 µm for A-D,F-H; in E, 2 µm for E.

Return to article