DNA methylation, also known as 5-methylcytosine, is an epigenetic modification that has crucial functions in plant growth, development and adaptation. The cellular DNA methylation level is tightly regulated by the combined action of DNA methyltransferases and demethylases. Protein complexes involved in the targeting and interpretation of DNA methylation have been identified, revealing intriguing roles of methyl-DNA binding proteins and molecular chaperones. Structural studies and in vitro reconstituted enzymatic systems have provided mechanistic insights into RNA-directed DNA methylation, the main pathway catalysing de novo methylation in plants. A better understanding of the regulatory mechanisms will enable locus-specific manipulation of the DNA methylation status. CRISPR–dCas9-based epigenome editing tools are being developed for this goal. Given that DNA methylation patterns can be stably transmitted through meiosis, and that large phenotypic variations can be contributed by epimutations, epigenome editing holds great promise in crop breeding by creating additional phenotypic variability on the same genetic material.

DNA甲基化，也称为5-甲基胞嘧啶，是一种表观遗传修饰，在植物生长、发育和适应中具有至关重要的功能。细胞 DNA 甲基化水平受到 DNA 甲基转移酶和去甲基化酶的联合作用的严格调节。参与 DNA 甲基化靶向和解释的蛋白质复合物已被鉴定，揭示了甲基 DNA 结合蛋白和分子伴侣的有趣作用。结构研究和体外重建酶系统为 RNA 指导的 DNA 甲基化（植物中催化从头甲基化的主要途径）提供了机制见解。更好地了解调控机制将使 DNA 甲基化状态的位点特异性操作成为可能。为此，正在开发基于 CRISPR-dCas9 的表观基因组编辑工具。鉴于DNA甲基化模式可以通过减数分裂稳定传递，并且表型突变可以导致大的表型变异，表观基因组编辑通过在相同的遗传物质上产生额外的表型变异，在作物育种中具有广阔的前景。