Fine structural changes in theDrosophila oocyte nucleus during a short period of RNA synthesis

Summary H³-uridine was injected into the abdomen ofD. melanogaster andD. immigrans and after 10, 30, 60 and 120 min of incorporation, the ovaries were prepared for autoradiography. The oocyte nucleus was found to synthesize RNA during a short period of vitellogenesis (stage 10A). Ultrastructural studies of the oocyte nucleus were made at the stage active in RNA synthesis and many electron-dense structures were found to appear at this time. Since none of these structures resembled nucleoli in fine structure, it is suggested that the RNA synthesized is non-ribosomal. Other ultrastructural modifications of the oooyte nucleus are presented and discussed.

---

Zusammenfassung H³-Uridin wurde in die Abdomina vonDrosophila melanogaster undDrosophila immigrans injiziert, und nach 10, 30, 60 und 120 min wurden die Ovarien für Autoradiographie präpariert. Es wurde gefunden, daß der Oozytenkern während einer kurzen Periode der Vitellogenese (Stadium 10A) RNS synthetisiert. Der Oozytenkern dieses Stadiums wurde elektronenmikroskopisch untersucht. Es zeigte sich, daß während dieses Stadiums elektronendichte Strukturen erscheinen. Keine dieser Strukturen sieht Nukleolen ähnlich in der Feinstruktur. Es wird deshalb angenommen, daß die synthetisierte RNS nicht ribosomale RNS ist. Auch andere feinstrukturelle Modifikationen wurden im Oozytenkern gefunden und werden hier beschrieben.

---

---

The authors wish to acknowledge the support of the National Science Foundation, Grants GB-5155, GB-5780 and GB-7980.     

A germline-specific gap junction protein required for survival of differentiating early germ cells

Germ cells require intimate associations and signals from the surrounding somatic cells throughout gametogenesis. The zero population growth (zpg) locus of Drosophila encodes a germline-specific gap junction protein, Innexin 4, that is required for survival of differentiating early germ cells during gametogenesis in both sexes. Animals with a null mutation in zpg are viable but sterile and have tiny gonads. Adult zpg-null gonads contain small numbers of early germ cells, resembling stem cells or early spermatogonia or oogonia, but lack later stages of germ cell differentiation. In the male, Zpg protein localizes to the surface of spermatogonia, primarily on the sides adjacent to the somatic cyst cells. In the female, Zpg protein localizes to germ cell surfaces, both those adjacent to surrounding somatic cells and those adjacent to other germ cells. We propose that Zpg-containing gap junctional hemichannels in the germ cell plasma membrane may connect with hemichannels made of other innexin isoforms on adjacent somatic cells. Gap junctional intercellular communication via these channels may mediate passage of crucial small molecules or signals between germline and somatic support cells required for survival and differentiation of early germ cells in both sexes.     

Isolation and partial chemical characterization of the three major yolk polypeptides from Drosophila melanogaster.

The three major yolk polypeptides of Drosophila melanogaster have been isolated from yolk spheres of early embryos. Their molecular weights, as determined by SDS-polyacrylamide electrophoresis, are 44,000, 45,000, and 46,000. A number of approaches have been used to show that each of these yolk polypeptides are different. They have different isoelectric points, they have different digestion products upon peptide mapping by limited proteolysis, and they show three different antigen-antibody systems when each polypeptide is reacted with an antisera made to a mixture of all three. Both the digestion with chymotrypsin and the immunoelectrophoresis studies indicate similarities between two of the polypeptides while the third appears unique. This is the first example of multiple yolk polypeptides of similar molecular weight.