FIG. 4.

V::Gus and V::Fsn accumulate in the pole plasm in a vas-dependent manner. (A to C) In a wild-type background, V::Gus driven by nosGal4 is expressed at low levels in germ line nuclei but accumulates to high levels in the cytoplasm surrounding the nurse cell nuclei. In the germ line cytoplasm, V::Gus is ubiquitous, but it is enriched in numerous luminous foci, particularly during the earlier stages of oogenesis. In the oocyte, V::Gus is enriched in the cortex but accumulates in the pole plasm during stage 10. In late oocytes, posterior V::Gus levels decrease. (D) Pole plasm accumulation of V::Gus is lost in vas mutants (compare with panel B). (E to I) V::Fsn driven by nosGal4 in a wild-type background during early oogenesis (notice that transgene expression follows the expression pattern of the driver) (E), stage 9 (F), stage 10 (G), stage 13 (H), and stage 14 (I). V::Fsn accumulates in nuclei and is uniformly distributed throughout the nurse cell cytoplasm. In the oocyte, the protein appears cortically enriched, and from stage 10 on, V::Fsn is enriched in the pole plasm. Posterior enrichment is not evident in mature eggs. (J) In a vas mutant background, pole plasm accumulation of V::Fsn is lost; however, a general cortical stain is still observed. Bars, 20 mm.