Epigenetic flexibility of plants

Methylation of a DNA molecule is one of several epigenetic mechanisms for controlling gene expression in cells, and acts as a signal to "turn" on and off the genes. In addition to regulating developmental processes in plants, the diversity of epigenetic mechanisms plays an important role in the phenotypic and physiological adaptability as well as the ability of plants to survive and reproduce in unpredictably changing environments. One of the basic epigenetic specificities of plants is the mechanism of RNA-directed DNA methylation (RdDM) de novo DNA methylation. RdDM requires a specialized transcription mechanism consisting of two plant-specific RNA polymerases - Pol IV and Pol V - and a large number of accessory proteins, but the mechanism is not fully elucidated. One hypothesis that will be discussed is the potential of RdDM in balancing the active and inactive status of target genes.