Gene

Biology

Epigenetics

Transposable element

DNA methylation

Genetics

Genome

RNA-Directed DNA Methylation

Methylation

Gene expression

Nature Reviews Genetics

RNA-directed DNA methylation (RdDM) is a major mechanism of transcriptional gene silencing in plants that is mediated through small interfering RNAs (siRNAs) and plant-specific RNA polymerases. This Review summarizes our latest understanding of RdDM, including its genomic targets, molecular mechanisms (such as emerging non-canonical pathways) and diverse biological roles. RNA-directed DNA methylation (RdDM) is the major small RNA-mediated epigenetic pathway in plants. RdDM requires a specialized transcriptional machinery that comprises two plant-specific RNA polymerases — Pol IV and Pol V — and a growing number of accessory proteins, the functions of which in the RdDM mechanism are only partially understood. Recent work has revealed variations in the canonical RdDM pathway and identified factors that recruit Pol IV and Pol V to specific target sequences. RdDM, which transcriptionally represses a subset of transposons and genes, is implicated in pathogen defence, stress responses and reproduction, as well as in interallelic and intercellular communication.

RNA-directed DNA methylation: an epigenetic pathway of increasing complexity