Rapid evolution of promoters from germline-specifically expressed genes including transposon silencing factors

Abstract

BackgroundThe piRNA pathway in animal gonads functions as an ‘RNA-based immune system’, serving to silence transposable elements and prevent inheritance of novel invaders. InDrosophila, this pathway relies on three gonad-specific Argonaute proteins (Argonaute-3, Aubergine and Piwi) that associate with 23-28 nucleotide piRNAs, directing the silencing of transposon-derived transcripts. Transposons constitute a primary driver of genome evolution, yet the evolution of piRNA pathway factors has not received in-depth exploration. Specifically, channel nuclear pore proteins, which impact piRNA processing, exhibit regions of rapid evolution in their promoters. Consequently, the question arises whether such a mode of evolution is a general feature of transposon silencing pathways.ResultsBy employing phylogenomic analysis of coding and promoter regions within genes that function in transposon silencing inDrosophila, we demonstrate that the promoters of germ cell-specific piRNA factors are undergoing rapid evolution. Our findings indicate that rapid promoter evolution is a common trait among piRNA factors engaged in germline silencing across insect species, potentially contributing to gene expression divergence in closely related taxa. Furthermore, we observe that the promoters of genes exclusively expressed in germ cells generally exhibit rapid evolution, which correlates with divergent gene expression.ConclusionsOur results suggest that promoter evolution could have wide impact on transposon silencing and evolution of species through differential expression of genes driven by invading transposons.