RNA Directed DNA Methylation (RdDM) is a pathway that mediates de novo DNA methylation, an evolutionary conserved chemical modification of cytosine bases, which exists in living organisms and utilizes small interfering RNA. Plants utilize DNA methylation for transposable element (TE) repression, regulation of gene expression and developmental regulation. TE activity strongly influences genome size and evolution, therefore making DNA methylation a key component in understanding divergence in genome evolution among seed plants. Multiple proteins that have extensively been studied in model plant Arabidopsis thaliana catalyze RNA dependent DNA Methylation pathway along with small interfering RNA. Several developmental functions have also been attributed to DNA methylation. This review will highlight aspects of RdDM pathway dynamics, evolution and functions in seed plants with focus on recent findings on conserved and non-conserved attributes between angiosperms and gymnosperms to potentially explain how methylation has impacted variations in evolutionary and developmental complexity among them and advance current understanding of this crucial epigenetic pathway.

RNA指导的DNA甲基化（RdDM）是介导从头DNA甲基化的一种途径，DNA甲基化是胞嘧啶碱基的进化保守化学修饰，存在于活生物体中，并利用小的干扰RNA。植物利用DNA甲基化进行转座因子（TE）抑制，基因表达调控和发育调控。TE活性强烈影响基因组的大小和进化，因此使DNA甲基化成为了解种子植物之间基因组进化差异的关键组成部分。在模型植物拟南芥中广泛研究了多种蛋白质与小干扰RNA一起催化RNA依赖的DNA甲基化途径。几种发育功能也归因于DNA甲基化。这篇综述将重点介绍种子植物中RdDM途径动力学，进化和功能的各个方面，重点是关于被子植物和裸子植物之间保守和非保守属性的最新发现，以潜在地解释甲基化如何影响它们之间进化和发育复杂性的变化并促进当前发展。对这一至关重要的表观遗传途径的理解。