The role of DNA methylation in transposable element silencing and genomic imprinting

Abstract

Recent studies in molecular genetics and genomics have shown the significance of DNA methylation in transposable element (TE) silencing and genomic imprinting in plants. Transcriptional silencing of TEs is maintained ubiquitously by DNA methylation, whereas repressing transposition of TEs requires additional and specific mechanisms. The host genome utilizes RNA-directed DNA methylation (RdDM) to repress TEs that is activated by transient loss of DNA methylation. In pollen vegetative cell and female central cell, which are companion cells in plant reproduction, DNA demethylation is observed and causes small interfering RNA (siRNA) accumulation. siRNAs are supposed to be the source of TE silencing in the sperm and egg cells by RdDM. Meanwhile, DNA demethylation in the central cell causes genomic imprinting. In plants, genomic imprinting is observed in the endosperm and controls seed development. Molecular action of DNA methylation in TE silencing and genomic imprinting will be applied to understanding that in developmental processes and environmental response.