Department of Plant Science, Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul 08826, Korea.
Molecular Breeding Division, National Academy of Agricultural Science, Rural Development Administration, Jeonju 54875, Korea.
Plant Physiol. 2019 Apr;179(4):1810-1821. doi: 10.1104/pp.18.01471. Epub 2019 Jan 28.
DNA methylation plays an important role in diverse developmental processes in many eukaryotes, including the response to environmental stress. Abscisic acid (ABA) is a plant hormone that is up-regulated under stress. The involvement of DNA methylation in the ABA response has been reported but is poorly understood. DNA demethylation is a reverse process of DNA methylation and often induces structural changes of chromatin leading to transcriptional activation. In Arabidopsis (, active DNA demethylation depends on the activity of REPRESSOR OF SILENCING 1 (ROS1), which directly excises 5-methylcytosine from DNA. Here we showed that mutants were hypersensitive to ABA during early seedling development and root elongation. Expression levels of some ABA-inducible genes were decreased in mutants, and more than 60% of their proximal regions became hypermethylated, indicating that a subset of ABA-inducible genes are under the regulation of ROS1-dependent DNA demethylation. Notable among them is () that encodes an enzyme that converts nicotinamide to nicotinic acid in the NAD salvage pathway. Many enzymes in this pathway are known to be involved in stress responses. The mutants display hypersensitivity to ABA, whereas overexpression of restores normal ABA responses. Our data suggest that is responsive to ABA but requires ROS1-mediated DNA demethylation at the promoter as a prerequisite to transcriptional activation. These findings suggest that ROS1-induced active DNA demethylation maintains the active state of transcription in response to ABA.
DNA 甲基化在许多真核生物的多种发育过程中发挥重要作用，包括对环境胁迫的反应。脱落酸（ABA）是一种在胁迫下上调的植物激素。已经报道了 DNA 甲基化在 ABA 反应中的参与，但知之甚少。DNA 去甲基化是 DNA 甲基化的反向过程，通常会诱导染色质结构变化，从而导致转录激活。在拟南芥中，（，活性 DNA 去甲基化依赖于沉默抑制物 1（ROS1）的活性，ROS1 可直接从 DNA 中切除 5-甲基胞嘧啶。在这里，我们表明 突变体在早期幼苗发育和根伸长过程中对 ABA 敏感。一些 ABA 诱导基因的表达水平在 突变体中降低，其近端区域的 60%以上发生超甲基化，表明一部分 ABA 诱导基因受 ROS1 依赖性 DNA 去甲基化调控。其中值得注意的是 （），它编码一种在 NAD 补救途径中将烟酰胺转化为烟酸的酶。该途径中的许多酶已知参与应激反应。 突变体对 ABA 敏感，而过表达 则恢复正常的 ABA 反应。我们的数据表明 对 ABA 有反应，但需要 ROS1 介导的启动子 DNA 去甲基化作为转录激活的前提。这些发现表明，ROS1 诱导的活性 DNA 去甲基化维持了 转录对 ABA 的活性状态。
