Solitary and synaptonemal complex-associated recombination nodules in pro-nurse cells during oogenesis in Drosophila melanogaster.

An oocyte in Drosophila melanogaster originates from 1 of 16 cells comprising an ovarial syncytium. The two pro-oocytes proceed into the pachytene stage of meiosis, but only one develops further into a mature oocyte while the other reverts to a nurse cell. It is known that pro-nurse cells also enter meiosis, as they contain incomplete synaptonemal complexes (SCs). We now show that these cells also harbour recombination nodules (RNs). In cells that only occasionally contain SC segments, the RNs are typically not located close to distinct tripartite SC structures. Instead, these RNs are frequently associated with a spherical body of amorphous material and two to three, more or less parallel fibres, possibly representing SC material. The significance of the solitary RNs is discussed in relation to the present knowledge of the assembly and disassembly of the SC.