Seed dormancy is an adaptive trait that is crucial to plant survival. Abscisic acid (ABA) is the primary phytohormone that induces seed dormancy. However, little is known about how the level of ABA in seeds is determined. Here we show that the Arabidopsis (Arabidopsis thaliana) H3K27me3 demethylase RELATIVE OF EARLY FLOWERING6 (REF6) suppresses seed dormancy by inducing ABA catabolism in seeds. Seeds of the ref6 loss-of-function mutants displayed enhanced dormancy that was associated with increased endogenous ABA content. We further show that the transcripts of two genes key to ABA catabolism, CYP707A1 and CYP707A3, but not genes involved in ABA biosynthesis, were significantly reduced in ref6 mutants during seed development and germination. In developing siliques, REF6 bound directly to CYP707A1 and CYP707A3, and was responsible for reducing their H3K27me3 levels. Genetic analysis demonstrated that the enhanced seed dormancy and ABA concentration in ref6 depended mainly on the reduced expression of CYP707A1 and CYP707A3. Conversely, overexpression of CYP707A1 could offset the enhanced seed dormancy of ref6. Taken together, our results revealed an epigenetic regulation mechanism that is involved in the regulation of ABA content in seeds.

种子休眠是对植物存活至关重要的适应性状。脱落酸（ABA）是诱导种子休眠的主要植物激素。但是，对于如何确定种子中ABA的水平知之甚少。在这里，我们显示了拟南芥H3K27me3脱甲基酶相对于早期开花6（REF6）可以通过诱导种子中的ABA分解代谢来抑制种子的休眠。ref6功能丧失突变体的种子显示出增强的休眠状态，这与内源性ABA含量增加有关。我们进一步显示，在种子发育和萌发期间，ref6突变体中，ABA分解代谢的两个关键基因CYP707A1和CYP707A3的转录本显着降低，但不参与ABA生物合成的基因。在开发的孤群中，REF6直接与CYP707A1和CYP707A3结合，并负责降低其H3K27me3水平。遗传分析表明ref6的种子休眠和ABA浓度增加主要取决于CYP707A1和CYP707A3的表达减少。相反，CYP707A1的过表达可能抵消了ref6增强的种子休眠。综上所述，我们的结果揭示了一种表观遗传调控机制，涉及种子中ABA含量的调控。