Specifications of Targeting Heterochromatin Modifications in Plants

Mol Plant. 2018 Mar 5;11(3):381-387. doi: 10.1016/j.molp.2017.10.002. Epub 2017 Oct 13.

Abstract

Plants encode a diverse repertoire of DNA methyltransferases that have specialized to target cytosines for methylation in specific sequence contexts. These include the de novo methyltransferase, DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM2), which methylates cytosines in all sequence contexts through an RNA-guided process, the CHROMOMETHYLASES (CMTs), which methylate CHH and CHG cytosines (where H is A, T, or C), and METHYLTRANSFERASE 1 (MET1), which maintains methylation of symmetrical CG contexts. In this review, we discuss the sequence specificities and targeting of each of these pathways. In particular, we highlight recent studies that indicate CMTs preferentially target CWG or CWA/CAW motifs (where W is A or T), and discuss how self-reinforcing feedback loops between DNA methyltransferases and histone modifications characteristic of heterochromatin specify targeting. Finally, the initiating events that lead to gene body methylation are discussed as a model illustrating how interdependent targeting of different silencing pathways can potentiate the establishment of off-target epialleles.

Keywords: DNA methylation; DNA methyltransferase; chromomethylase; epiallele; gene body methylation; heterochromatin.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • DNA (Cytosine-5-)-Methyltransferases / genetics
  • DNA (Cytosine-5-)-Methyltransferases / metabolism
  • DNA Methylation / genetics
  • DNA Methylation / physiology*
  • Gene Expression Regulation, Plant / genetics
  • Gene Expression Regulation, Plant / physiology
  • Heterochromatin / genetics
  • Heterochromatin / metabolism*
  • Models, Biological

Substances

  • Arabidopsis Proteins
  • Heterochromatin
  • DNA (Cytosine-5-)-Methyltransferases
  • chromomethylase