Leaf senescence is driven by the expression of senescence-associated genes (SAGs). Development-specific genes often undergo DNA demethylation in their promoter and other regions, which regulates gene expression. Whether and how DNA demethylation regulates the expression of SAGs and thus leaf senescence remain elusive. Whole-genome bisulfite sequencing (WGBS) analyses of wild-type (WT) and demeter-like 3 (dml3) Arabidopsis leaves at three developmental stages revealed hypermethylation during leaf senescence in dml3 compared with WT, and 20 556 differentially methylated regions (DMRs) were identified by comparing the methylomes of dml3 and WT in the CG, CHG, and CHH contexts. Furthermore, we identified that 335 DMR-associated genes (DMGs), such as NAC016 and SEN1, are upregulated during leaf senescence, and found an inverse correlation between the DNA methylation levels (especially in the promoter regions) and the transcript abundances of the related SAGs in WT. In contrast, in dml3 the promoters of SAGs were hypermethylated and their transcript levels were remarkably reduced, and leaf senescence was significantly delayed. Collectively, our study unraveled a novel epigenetic regulatory mechanism underlying leaf senescence in which DML3 is expressed at the onset of and during senescence to demethylate promoter, gene body or 3′ UTR regions to activate a set of SAGs.

叶片衰老由衰老相关基因（SAG）的表达驱动。发育特异性基因通常在其启动子和其他区域经历DNA去甲基化作用，从而调节基因表达。DNA脱甲基化是否以及如何调节SAG的表达，从而调节叶片的衰老仍然不清楚。对野生型（WT）和demeter样3（dml3）拟南芥叶片在三个发育阶段的全基因组亚硫酸氢盐测序（WGBS）分析显示，与WT相比，dml3中的叶片衰老过程中甲基化程度高，并且有20 556个差异甲基化区域（DMRs）通过比较dml3的甲基化组来鉴定以及CG，CHG和CHH上下文中的WT。此外，我们确定了335个DMR相关基因（DMG），例如NAC016和SEN1，在叶片衰老过程中被上调，并且发现DNA甲基化水平（尤其是在启动子区域）与相关转录本的丰度呈负相关。WT中的SAG。相反，在dml3的启动子凹陷被超甲基化和它们的转录物水平显着降低，并且叶子衰老被延迟显著。总的来说，我们的研究揭示了一种新的表观遗传调控机制，该机制涉及叶片衰老，其中DML3脱氧核糖核酸在去甲基化启动子，基因体或3'UTR区开始并在衰老期间表达以激活一组SAG。