DNA demethylation is important for the erasure of DNA methylation. The role of DNA demethylation in plant development remains poorly understood. Here, we found extensive DNA demethylation in the CHH context around pericentromeric regions and DNA demethylation in the CG, CHG, and CHH contexts at discrete genomic regions during ectopic xylem tracheary element (TE) differentiation. While loss of pericentromeric methylation occurs passively, DNA demethylation at a subset of regions relies on active DNA demethylation initiated by DNA glycosylases ROS1, DML2, and DML3. The ros1 and rdd mutations impair ectopic TE differentiation and xylem development in the young roots of Arabidopsis seedlings. Active DNA demethylation targets and regulates many genes for TE differentiation. The defect of xylem development in rdd is proposed to be caused by dysregulation of multiple genes. Our study identifies a role of active DNA demethylation in vascular development and reveals an epigenetic mechanism for TE differentiation.

DNA去甲基化对于消除DNA甲基化很重要。DNA去甲基化在植物发育中的作用仍然知之甚少。在这里，我们发现在异位木质部气管元件 (TE) 分化过程中，在离着丝粒周围区域的 CHH 环境中存在广泛的 DNA 去甲基化，在离散基因组区域的 CG、CHG 和 CHH 环境中发现了 DNA 去甲基化。虽然着丝粒周围甲基化的丧失是被动发生的，但部分区域的 DNA 去甲基化依赖于由 DNA 糖基化酶 ROS1、DML2 和 DML3 引发的主动 DNA 去甲基化。ros1和rdd突变损害拟南芥幼根的异位 TE 分化和木质部发育幼苗。活性 DNA 去甲基化靶向并调节许多用于 TE 分化的基因。rdd中木质部发育的缺陷被认为是由多个基因的失调引起的。我们的研究确定了活性 DNA 去甲基化在血管发育中的作用，并揭示了 TE 分化的表观遗传机制。