A rapid change in P-element-induced hybrid dysgenesis status in Ukrainian populations of Drosophila melanogaster.

The Drosophila melanogaster P-transposable element is an example of mobile DNA transferred horizontally and known to have spread globally over the last 50-60 years. In Drosophila, the P-element causes a syndrome known as 'P-M hybrid dysgenesis' that obstructs normal ovary development in the female progeny of susceptible populations. Despite extensive research, the stability and global population dynamics of P-M dysgenic phenotypes remain poorly understood. Here, we report a recent and rapid transition in the P-M status of D. melanogaster populations from Ukraine. We demonstrate that these populations are currently dominated by the P'-cytotype characterized by active genomic P-elements and unknown from Ukraine just two decades ago. Our results suggest a recent invasion of the P-element in Ukraine, a pattern that matches recent discoveries from Turkey.

On the persistence of P element in cultured lineages of Drosophila melanogaster.

P transposon is known to have invaded the Drosophila melanogaster genome in the 1950s as a result of horizontal transmission from D. willistoni. Part of the evidence supporting the timing of its invasion comes from analyses of cultured drosophila lineages originating from wild flies cultivated long time in laboratory before analysis. Such analyses have shown that P element was absent from the genomes of cultured lineages established from wild flies caught from the wild before the 1950s. Although the hypothesis of P element transmission has obtained multiple lines of evidence and is beyond doubt today, we decided to test whether analysis of cultured lineages can provide some temporal information on the P element population dynamics. In the present work we demonstrate that P element present the in wild-caught flies may be lost in the cultured fly lineages after some generations. This result is in accordance with the results of at least one published work and suggests that analysis of the cultured fly lineages may sometimes be unreliable in establishing historical trends in P element population dynamics, as the transposon may be occasionally lost, perhaps in the highly inbred lineages in which not all founding females carry it.

DNA methylation in Drosophila melanogaster may depend on lineage heterogeneity.

DNA methylation has been discovered in Drosophila only recently. Current evidence indicates that de novo methylation patterns in drosophila are maintained in a different way compared to vertebrates and plants. As the genomic role and determinants of DNA methylation are poorly understood in invertebrates, its link with several factors has been suggested. In this study, we tested for the putative link between DNA methylation patterns in Drosophila melanogaster and radiation or the activity of P transposon. Neither of the links was apparent from the results, however, we obtained some hints on a possible link between DNA methylation pattern and genomic heterogeneity of fly lineages.