Comparative epigenomics: A powerful tool to understand the evolution of DNA methylation

Understanding how developmental and functional complexity of organisms evolves is a longstanding challenge in biology. Genetic mutation has long been thought to be the cause of biological complexity. However, increasing evidence indicates that epigenetic variation provides a parallel path for the evolution of biological complexity. Cytosine DNA methylation, the addition of a chemical mark on DNA, is a conserved and essential gene regulatory mechanism. Recent studies have greatly advanced our understanding of the DNA methylation landscapes and key regulatory components across many species. In this review, I summarize recent advances in understanding DNA methylation from an evolutionary perspective. Using comparative approaches, I highlight the conservation and divergence of DNA methylation patterns and regulatory machinery in plants and other eukaryotic organisms.