Active DNA Demethylation in Plant Companion Cells Reinforces Transposon Methylation in Gametes

Christian Ibarra(University of California, Berkeley), Xiaoqi Feng(University of California, Berkeley), Vera K. Schoft(Gregor Mendel Institute of Molecular Plant Biology), Tzung‐Fu Hsieh(University of California, Berkeley), Rie Uzawa(University of California, Berkeley), Jessica A. Rodrigues(University of California, Berkeley), Assaf Zemach(University of California, Berkeley), Nina Chumak(Gregor Mendel Institute of Molecular Plant Biology), Adriana Machlicova(Gregor Mendel Institute of Molecular Plant Biology), Toshiro Nishimura(University of California, Berkeley), Denisse Rojas(University of California, Berkeley), Robert L. Fischer(University of California, Berkeley), Hisashi Tamaru(Gregor Mendel Institute of Molecular Plant Biology), Daniel Zilberman(University of California, Berkeley)
Science
September 14, 2012
10.1126/science.1224839
Cited by 525Open Access

Abstract

The Arabidopsis thaliana central cell, the companion cell of the egg, undergoes DNA demethylation before fertilization, but the targeting preferences, mechanism, and biological significance of this process remain unclear. Here, we show that active DNA demethylation mediated by the DEMETER DNA glycosylase accounts for all of the demethylation in the central cell and preferentially targets small, AT-rich, and nucleosome-depleted euchromatic transposable elements. The vegetative cell, the companion cell of sperm, also undergoes DEMETER-dependent demethylation of similar sequences, and lack of DEMETER in vegetative cells causes reduced small RNA-directed DNA methylation of transposons in sperm. Our results demonstrate that demethylation in companion cells reinforces transposon methylation in plant gametes and likely contributes to stable silencing of transposable elements across generations.

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