DNA methylation — an essential mechanism in plant molecular biology

Abstract

DNA methylation is a common phenomenon in plants. In plant genomes, its level is comparatively lower than that of animal genomes. It is involved in gene regulation and controls many development pathways. Methylation status of particular DNA sequence controls the potential for transition from vegetative to reproductive growth. It is believed that fully methylated elements are genetically and transcriptionally silent, however, some methylated genes may also be expressed. While hypomethylated elements are active and partially methylated elements, designated programmable, exhibit a variety of development expression programmes during plant development. DNA methylation plays an important role in the evolution of plant species through alloploidy or polyploidy. The methylation pattern in parental plants is highly heritable which is of great interest for plant breeders. DNA methylation also plays an important role in genome defense system by inactivating and methylating the invasive DNA sequences. A methylated sequence may suppress gene expression in other sequences. The generation and breeding of transgenic plants becomes complex due to inactivation of transgenes and instability of their expression. The pattern of methylation is maintained by methyltransferase through DNA replication. Several methods are in use to detect methylated nucleotides motifs that may help in identification of some essential genes.