Molecular mechanisms and biological functions of active DNA demethylation in plants

DNA methylation is a conserved epigenetic modification that plays important roles in silencing transposable elements, regulating gene expression, and maintaining genome stability. In plants, DNA methylation is de novo established by the RNA-directed DNA methylation pathway and maintained during each cell cycle. It can be actively removed by the REPRESSOR OF SILENCING 1/DEMETER family proteins through the base excision repair pathway. Active DNA demethylation is essential for plant growth, development, reproduction and stress adaptation. During the past two decades, significant progress has been made in our understanding of active DNA demethylation. In this review, we will discuss the molecular mechanisms, regulation, and biological functions of active DNA demethylation in plants.