Abstract
In the Drosophila ovarian follicle, 15 polyploid nurse cells (NC) are linked by cytoplasmic bridges to the anterior pole of the oocyte. The mutant dicephalic occasionally produces aberrant follicles whose 15 nurse cells are separated into two clusters, each attached to one oocyte pole [split nurse cell (SNC) follicles]. Feulgen cytophotometry of isolated nuclei from such clusters and from normal follicles of the same females revealed an inverse correlation between NC number per cluster and mean DNA content per nucleus. The maximum DNA content of nuclei from split NC clusters falls into the 4,096 C class as opposed to the 2,048 C class in 15 NC clusters; the mean DNA content per NC nucleus is 1,940 C in the former and 1,340 C in the latter. These correlations are confirmed by measurements on follicles containing fewer or more than 15 NC, and on SNC follicles from another mutant (spindel C). These findings indicate that replication in NC nuclei is controlled with reference to the transcriptional capacity of the individual NC cluster rather than the total capacity available per oocyte or follicle. We discuss this finding with respect to embryonic patterning as influenced by nurse cell location and list and discuss conflicting published reports on over- and underreplication in Drosophila follicles.
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