Drosophila virilis Raw sequence reads

Among the described systems of hybrid dysgenesis (HD) in Drosophila, D. virilis syndrome represents a special case since it includes simultaneous mobilization of a set of TEs belonging to different classes. According to paradigm suggesting that the activity of asymmetric TEs found in only one parental strain is a ?ore driver of HD manifestations in the germline of dysgenic progeny most attention was paid to biology of asymmetric TE including Penelope, Paris, Helena and Polyphemus since active copies of these elements are abundant in the genome of P-like strain and absent in all M-like strains. However, there are several D. virilis strains lacking the above TEs in their genomes, but exhibiting “neutral” (N) cytotype which prevents the sterility in the progeny when females of such strains are crossed with males of P-like strain. Herein, using different M- and N-strains of D. virilis we monitored the activity of asymmetric TEs presumably involved in HD manifestations. To reach this goal, we assessed the activity of HD-related TEs in terms of mRNA and piRNAs expression in the ovaries of these strains and interstrain hybrids and demonstrated that N-strains show high heterogeneity in terms of the presence and expression of Penelope, Paris and Polyphemus. Furthermore, the investigation of transgenic strains containing several functional Penelope copies and correspondent piRNAs demonstrated that these strains preserved M-like cytotype characteristic for the original strain. On the other hand, we have witnessed cytotype shift (from N to M) in a strain devoid of all four HD-related TEs. Surprisingly, we observed almost equal levels of piRNA homologous to asymmetric TEs in the F1 ovaries from reciprocal and dysgenic crosses. Overall, our data suggest that derepression of known asymmetric TEs in dysgenic crosses is unlikely the only trigger of HD manifestations in D. virilis.