Graduate student North Carolina State University Kannapolis, North Carolina
Body of Abstract: The Arabidopsis DEMETER (DME) is a plant DNA 5-methyl cytosine glycosylase that demethylates the genome in the central cell and is essential for seed viability. DME specifically demethylates around ten thousand target sites, which contains gene flanking small TEs in euchromatic regions, intergenic sequences, and heterochromatic targets. Previously, we have shown that the C-terminal half of DME (CTD) retains both catalytic glycosylase activity as well as targeting function. Here we focus on one of the domain within the CTD, the CXXC domain, as this domain in mammals has been implicated in chromatin protein localization. Our results show that while DME with an impaired CXXC domain has a mild effect on the 5mC excision enzymatic activity in vitro, the CXXC domain is required for a robust and consistent in vivo DME function of preventing seed abortion. Whole genome methylome analysis of dme mutant endosperm complemented with a CXXC-mutated CTD transgene revealed that the canonical DME target sites are largely demethylated, indicating that the CXXC domain is needed to ensure efficient demethylation but is dispensable for DME localization to its target sites.