Noncoding RNA-Mediated Regulation of DNA Methylation: Insights into Plant Epigenetic Mechanisms

Cytosine methylation (5mC) of DNA is a conserved epigenetic mark important for plant growth and development. Extensive studies have been conducted to elucidate the regulatory processes governing DNA methylation and demethylation in both plants and animals under normal and stress conditions. Plants possess specific DNA methyltransferase enzymes that establish and maintain DNA methylation in all sequence contexts (CG, CHH, CHG) within targeted regions of both euchromatin and heterochromatin on the chromosomes. Various epigenetic marks rely on each other and are interconnected for their establishment and maintenance. Long noncoding RNAs regulate genomic organization, chromatin structure, compaction, and genome stability. These noncoding RNAs are categorized by their functions and formations, which display considerable diversity in DNA methylation among different plant species. Transcriptionally, the abundance of noncoding RNA is controlled by various epigenetic modifications, especially DNA methylation. Due to their participation in several epigenetic and genetic regulatory mechanisms, small interfering RNAs (siRNAs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) may influence developmental processes, stress responses, and adaptability. This review offers a comprehensive summary of the latest advancements in understanding the intricate relationship between DNA methylation and noncoding RNAs. It delves into the processes involved in their interdependence, particularly in the establishment and maintenance of DNA methylation within targeted regions.