Characterizing the Novel Roles of Small RNA-directed DNA Methylation in the Epigenetic Regulation of Athila Family Retrotransposons

Transposable elements (TEs) are sequences of DNA that possess the ability to mobilize from one location of a host genome to another. TEs are often called “jumping genes” and are present in the genome of nearly every eukaryote, including humans. TE activity is extremely harmful to an organism, as their jumping is able to cause significant mutations and phenotypes. To repress this mutagenic potential, the eukaryotic genome has evolved various defense mechanisms to silence TE activity. Several of these mechanisms achieve the silencing of TEs while avoiding an underlying change in the DNA sequence through a process known as epigenetic regulation. Two particular epigenetic pathways in the model organism Arabidopsis Thaliana work to ensure that TEs are silenced and unable to cause significant damage to the genome. The first pathway, RNA-dependent DNA Methylation (RdDM), works to establish and maintain the methylation of TEs. The second pathway, RNA interference (RNAi), degrades the RNA intermediates of expressed TEs to prevent them from inserting themselves into the host genome. The mechanism for the epigenetic resilencing of TEs was thought to be that of the RdDM pathway. However, our lab has recently shown that small interfering RNAs generated by the RNAi pathway are necessary for the complete transcriptional resilencing of TEs through a pathway we have termed RDR6-RdDM. Through the analysis of small RNA levels as well as TE expression and DNA methylation levels, I have identified multiple components of the RDR6-RdDM pathway which are necessary for epigenetic resilencing of active TEsNational Science Foundation Research Experience for Undergraduates Awarded as a Supplement to the Slotkin Grant MCB-1020499Arts and Sciences Undergraduate Research ScholarshipElizabeth Wagner ScholarshipSummer Undergraduate Research Fellowship through the American Society of Plant BiologyA one-year embargo was granted for this item.Academic Major: Molecular Genetic