PENELOPE, A NEW FAMILY OF TRANSPOSABLE ELEMENTS AND ITS POSSIBLE ROLEIN HYBRID DYSGENESIS IN DROSOPHILA-VIRILIS

A hybrid dysgenesis syndrome occurs in Drosophila virilis when males f rom an established laboratory strain are crossed to females obtained f rom the wild, causing the simultaneous mobilization of several differe nt transposable elements, The insertion sequence responsible for the m utant phenotype of a dysgenic yellow allele has been characterized and named Penelope. In situ hybridization and Southern analyses reveal th e presence of more than 30 copies of this element in the beta-like par ental strain, whereas Penelope is absent in all M-like strains tested, Penelope contains one 2.5-kb-long ORF that could encode products with homology to integrase and reverse transcriptase. Northern analysis an d whole-mount in situ hybridization show strong induction of a 2.6-kb RNA in the ovaries of dysgenic females that is expressed at very low l evels in the parental strains or in the progeny from the reciprocal cr oss, Injection of Penelope-containing plasmids into preblastoderm embr yos of an M-like strain results in mutant progeny caused by insertion of Ulysses and perhaps other transposons, suggesting that Penelope exp ression might be responsible for the observed dysgenesis syndrome and the simultaneous mobilization of other transposable elements.