• Dimethylation of histone H3 at lysine 9 (H3K9me2) is associated with heterochromatinization and transcriptional gene silencing in plants. The activation of sets of genes by drought stress is correlated with reduced H3K9me2 levels, but the role of H3K9 methylation in the regulation of drought-stress responses remains elusive.
• Here, we show that the Jumonji domain-containing H3K9 demethylase JMJ27 positively regulates drought-stress responses through its histone demethylase activity. RNA-seq analysis identified JMJ27-regulated genes, including positive regulators of drought stress GALACTINOL SYNTHASE 2 (GOLS2) and RESPONSE TO DESICCATION 20 (RD20). Genetic analysis demonstrated that JMJ27 positively regulates drought-stress responses at least partly through GOLS2 and RD20.
• JMJ27 directly associated with GOLS2 and RD20, and protected these loci from silencing by reducing H3K9me2 levels under normal conditions. REGULATORY PARTICLE NON-ATPASE 1a (RPN1a), a subunit of the 26S proteasome, interacted with JMJ27 and negatively regulated JMJ27 accumulation. Drought stress diminished RPN1a abundance, resulting in increased JMJ27 abundance. The drought stress-promoted occupancy of JMJ27 at GOLS2 and RD20 chromatin may reinforce their transcriptional induction by locally reducing the H3K9me2 levels.
• These results indicate that the RPN1a-JMJ27 module precisely regulates dynamic H3K9me2 deposition plasticity, ensuring proper adaptation to drought stress in Arabidopsis.

中文翻译：

---

JMJ27 介导的组蛋白 H3K9 去甲基化正向调节拟南芥的干旱胁迫反应

• 组蛋白 H3 在赖氨酸 9 (H3K9me2) 的二甲基化与植物中的异染色质化和转录基因沉默有关。干旱胁迫对基因组的激活与 H3K9me2 水平降低相关，但 H3K9 甲基化在调节干旱胁迫反应中的作用仍然难以捉摸。
• 在这里，我们显示含有 Jumonji 结构域的 H3K9 去甲基化酶 JMJ27 通过其组蛋白去甲基化酶活性正向调节干旱胁迫反应。RNA-seq 分析确定了 JMJ27 调节的基因，包括干旱胁迫半乳糖醇合成酶 2 ( GOLS2 ) 和RESPONSE TO DESICCATION 20 ( RD20 ) 的正调节因子。遗传分析表明，JMJ27 至少部分通过GOLS2和RD20正向调节干旱胁迫反应。
• JMJ27 与GOLS2和RD20直接相关，并通过在正常条件下降低 H3K9me2 水平来保护这些基因座免于沉默。调节颗粒非ATP酶1a (RPN1a)是26S蛋白酶体的一个亚基，与JMJ27相互作用并负调控JMJ27的积累。干旱胁迫降低了 RPN1a 丰度，导致 JMJ27 丰度增加。干旱胁迫促进 JMJ27 在GOLS2和RD20染色质上的占有率可能通过局部降低 H3K9me2 水平来增强它们的转录诱导。
• 这些结果表明，RPN1a-JMJ27 模块精确地调节动态 H3K9me2 沉积可塑性，确保对拟南芥干旱胁迫的适当适应。