Lampbrush loop-specific protein of Drosophila hydei.

By immunofluorescence techniques and protein blotting experiments we have shown that an antiserum specifically reacts with a Mr 80,000 protein (the "Ps protein") in the lampbrush loop " pseudonucleolus " in spermatocyte nuclei of Drosophila hydei. Comparative studies of X/Y and X/0 testes indicate that the gene encoding the Ps protein is not located on the Y chromosome but on an autosome or the X chromosome. The Ps protein is tissue specific. It is likely to be a rather conserved protein since the antigenic determinant recognized by the antiserum could be detected in the spermatocyte nuclei of a number of other Drosophila species. For those species with prominent Y chromosomal lampbrush loops, it could be shown that the cross-reaction is, as in D. hydei, associated with a specific Y chromosomal loop.