Investigation of piRNA-mediated Silencing in Drosophila Virilis

piRNAs are a class of small non-coding RNA that plays a crucial role in regulating the expression of transposable elements (TEs) in animal gonads. This regulation occurs at both the transcriptional and post-transcriptional levels, through the complementary recognition between piRNAs and RNA target. piRNAs originate from specific genomic loci known as piRNA clusters, which are composed of fragments of TE sequences. Individual TE insertions can also transform to piRNA clusters. In rare cases, piRNA-guided gene silencing can occur when the piRNA complex mistakenly targets genes located in the proximity of TE insertions, leading to the suppression of their expression and the formation of piRNA-based gene silencing. The precise mechanisms by which the organism adapts to this gene silencing process are poorly understood. However, these examples suggest that piRNAs may play a tissue-specific role in regulating gene expression in certain contexts. The phenomenon of paramutation describes an interaction between two alleles in which one allele (the paramutagenic allele) causes epigenetic changes in a homologous allele (the paramutable allele). The exact mechanism of this epigenetic modification is not fully understood, but the paramutation process in Drosophila involves the maternal transmission of piRNAs, which may contribute to the production of more piRNAs from the homologous locus. All genic piRNA clusters have the potential to exhibit paramutagenic properties. In this study, the repertoire of genic piRNAs in the ovaries of female Drosophila virilis from various geographical and laboratory populations was investigated. Genic piRNAs account for approximately 5% of the total piRNA pool in D. virilis ovaries and exhibit pronounced intraspecific differences. The paper describes in detail the loci of Adar, OtopLb, and RhoGEF3 genes, which are part of piRNA clusters. Maternal inheritance of piRNAs has been shown to be a necessary factor in determining the formation of piRNAs in subsequent generations. However, maternal transmission of piRNAs to the Adar, OtopLb, and RhoGEF3 loci is not sufficient for epigenetic reprogramming of homologous loci due to paramutation. It is likely that the structure of the genetic loci determines their susceptibility to epigenetic modification by paramutation.