CYTOSKELETON OF THE DROSOPHILA EGG CHAMBER - NEW OBSERVATIONS ON MICROFILAMENT DISTRIBUTION DURING OOCYTE GROWTH

The distribution of microfilaments in Drosophila egg chambers stained with rhodamine (Rh)-conjugated phalloidin was studied by laser scannin g confocal microscopy and transmission electron microscopy. These tech niques revealed new details in the pattern of microfilament localizati on. We observed in stage 1-3 egg chambers accumulation of filamentous actin in the oocyte cytoplasm between the ring canals connecting the o ocyte with adjacent nurse cells. Starting from stages 6-7 short microf ilament bundles arranged in basket-like structures were associated wit h the side of the ring canals facing the nurse cell cytoplasm. We also observed a dramatic decrease in the actin network associated with the cortex of the oocyte in stage 10. During stage 10B the nurse cell cyt oplasm was crossed by radial actin bundles that showed a sarcomeric-li ke cross striation after Rh-phalloidin staining. The ring canals also did not uniformly stain but showed a punctate labeling. The implicatio ns of the actin cytoskeleton during oocyte growth are discussed. (C) 1 995 Wiley-Liss, Inc.