Poster abstracts
Poster number 1 submitted by Dalen Fultz
Newly Introduced Transposable Elements are Silenced by Expression-Dependent RdDM
Dalen R. Fultz (The Ohio State University), R. Keith Slotkin (The Ohio State University)
Abstract:
Transposable Elements (TEs) are mobile regions of DNA that can cause mutations, changes in gene expression, and sterility when active. TEs make up large portions of plant genomes and can be horizontally transferred. In Arabidopsis, endogenous TEs and other targets of RNA-directed DNA Methylation (RdDM) have existed in the genome for many generations. These regions have moved beyond the initial steps of silencing and are no longer representative of early silencing events. The genome is equipped to recognize invading DNA such as transgenes, viruses, and horizontally transferred TEs. Yet, we have little understanding of how silencing pathways act during initial recognition. In order to study truly de novo silencing, we have introduced retrotransposons from Nicotiana tabacum (Tto1) and Schizosaccharomyces pombe (Tf1) into Arabidopsis. By investigating the first generation of plants that harbor these elements, we can determine the requirements of silencing initiation and the components required to transition from early phases of silencing to late. Unlike genic control transgenes, these TE-transgenes are targeted for DNA methylation and histone modification by small interfering RNAs. My data indicates that both RNA Polymerase IV mediated RdDM (Pol IV-RdDM) and Pol II expression-dependent RdDM (Pol II-RdDM) are capable of placing these marks, and that the latter acts independently of the former.
Keywords: RNAi, Transposable Element, DNA methlylation