Cytidine analogs in plant epigenetic research and beyond.

Abstract

Cytosine (DNA) methylation plays important roles in silencing transposable elements, plant development, genomic imprinting, stress responses, and maintenance of genome stability. To better understand the functions of this epigenetic modification, several tools have been developed to manipulate DNA methylation levels. These include mutants of DNA methylation writers and readers, targeted manipulation of locus-specific methylation, and the use of chemical inhibitors. Here, we summarize the effects of commonly used cytidine analog chemical inhibitors represented by zebularine, 5-azacytidine, and their related compounds on plants. These analogs are incorporated into the chromosomal DNA, where they block the activity of the replicative CG DNA methyltransferase 1 (MET1). This leads to manifold alterations in plant epigenome, modified developmental programs, or suppression of hybridization barriers. We also highlight the DNA-damaging effects of cytidine analogs, particularly the formation of stable DNA-protein crosslinks between DNA and MET1. This sheds new light on specific phenotypes observed upon cytidine analog treatments. In conclusion, cytidine analogs remain a vital tool for plant genome research and have the potential to open new promising avenues for applications in plant biotechnology and breeding.