A quantitative, genome-wide analysis in Drosophila reveals transposable elements' influence on gene expression is species-specific

Transposable elements (TEs) are parasite DNA sequences that are able to move and multiply along the chromosomes of all genomes. They can be controlled by the host through the targeting of silencing epigenetic marks, which may affect the chromatin structure of neighboring sequences, including genes. In this study, we used transcriptomic and epigenomic high-throughput data produced from ovarian samples of several Drosophila melanogaster and Drosophila simulans wild-type strains, in order to finely quantify the influence of TE insertions on gene RNA levels and histone marks (H3K9me3 and H3K4me3). Our results reveal a stronger epigenetic effect of TEs on ortholog genes in D. simulans compared to D. melanogaster. At the same time, we uncover a larger contribution of TEs to gene H3K9me3 variance within genomes in D. melanogaster, which is evidenced by a stronger correlation of TE numbers around genes with the levels of this chromatin mark in D. melanogaster. Overall, this work contributes to the understanding of species-specific influence of TEs within genomes. It provides a new light on the considerable natural variability provided by TEs, which may be associated with contrasted adaptive and evolutionary potentials. Significance StatementTransposable elements (TEs) are parasitic DNA sequences that are widespread components of all genomes. In this study, we combined genomic, transcriptomic and epigenomic high-throughput data produced from ovarian samples of Drosophila melanogaster and Drosophila simulans wild-type strains, in order to finely quantify the genome-wide influence of TE insertions on gene expression. Our results uncover contrasted patterns depending on the strain, which may have evolutionary impacts.