Poster abstracts
Poster number 23 submitted by Mowei Li
Cytosine methylation patterns associated with pl1 paramutation are reestablished and trans-chromosomally adopted during embryogeny
Mowei Li (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, OH, 43210), Natalie Deans (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, OH, 43210), Jay Hollick (Department of Molecular Genetics and Centers for Applied Plant Sciences and RNA Biology, The Ohio State University, Columbus, OH, 43210)
Abstract:
Paramutation describes specific meiotically heritable changes in gene regulation dependent on trans-homolog interactions. A highly expressed state (termed Pl-Rh) of the purple plant 1 (pl1) Pl1-Rhoades allele can be heritably suppressed in trans by a transcriptionally and post-transcriptionally repressed state (termed Pl'). This leads to heritable reduction in plant pigmentation in such heterozygotes and the persistence of weak pigmentation in subsequent progeny. Although the molecular mechanism remains largely unknown, forward genetic screens identify required to maintain repression (rmr) and mediator of paramutation (mop) loci affecting the paramutation process. Because most of the currently known RMR and MOP proteins are likely orthologs of Arabidopsis RNA-directed DNA methylation (RdDM) pathway components, it’s hypothesized that a similar pathway contributes to paramutation behaviors through 24-nucleotide (24nt) RNA-based recruitment of chromatin modifications like 5-methylcytosines (5mC). In day 8 seedlings, we found Pl' states have significant enrichment of 24nt RNAs at a small region of a penta-repeat ~12kb 3' of the pl1 coding region – coincident with 5mC in primarily CG and CHG contexts. Identical profiles were also seen in Pl-Rh / Pl' and Pl' / Pl-Rh seedlings indicating that Pl'-specific 5mC patterns are adopted by Pl-Rh during early development. Similar comparisons with 15 and 21 days after pollination (DAP) Pl-Rh / Pl' and Pl' / Pl-Rh developing embryos show a progressive reestablishment of Pl' like 5mC patterns with parent-of-origin differences that appear independent of 24nt sRNA levels. At 21 DAP in particular, 5mC in both CG and CHG contexts remained sparse in Pl-Rh / Pl' relative to Pl' / Pl-Rh. While the nature of these parent-of-origin differences remains speculative, our results point to the mid stages of embryogeny where 5mC patterns specified by meiotically-heritable information are elaborated.
Keywords: Epigenetics, Methylation