Expression of the C-Terminal Domain of Mammalian <i>TET</i>3 DNA Dioxygenase in <i>Arabidopsis thaliana</i> Induces Heritable Methylation Changes at <i>rDNA</i> Loci

Abstract

In plants, demethylation of 5-methylcytosine (5 mC) residues is controlled by DNA glycosylases, while in mammals it requires oxidation of 5 mC by TET proteins, a group of Fe(II)/2-oxoglutaratedependent dioxygenases. We analysed the effects of expressing the C-terminal catalytic domain of the human TET 3 gene ( TET 3c) in Arabidopsis thaliana , using an rDNA region as a methylation reporter. In TET3c transformants, epialleles with hypomethylation or hypermethylation patterns can be induced, which is each stably retained in progeny lines even after removal of the TET 3c transgene. In TET 3c transformants, 5-hydroxymethylcytosine (5 hmC) marks are detected, indicative of the oxidative activity of the transgenic enzyme. 5-formylcytosine (5 fC) is only detectable in TET3c transformants with a DNA glycosylase mutant background suggesting further oxidation of 5 hmC residues to 5 fC by TET 3c, and efficient recognition and removal of 5 fC by plant glycosylases. The results suggest that TET 3c can be employed to induce heritable locus-specific changes in DNA methylation, and that accumulation of 5 hmC can be used as a marker for TET 3c target regions.