Seed germination is a vital developmental process that is tightly controlled by environmental signals, ensuring germination under favorable conditions. High temperature (HT) suppresses seed germination. This process, known as thermoinhibition, is achieved by activating abscisic acid and inhibiting gibberellic acid biosynthesis. The zinc-finger protein SOMNUS (SOM) participates in thermoinhibition of seed germination by altering gibberellic acid/abscisic acid metabolism, but the underlying regulatory mechanism is poorly understood. In this study, we report that SOM binds to its own promoter and activates its own expression in Arabidopsis (Arabidopsis thaliana) and identify the MADS-box transcription factor AGAMOUS-LIKE67 (AGL67) as a critical player in SOM function, based on its ability to recognize CArG-boxes within the SOM promoter and mediate the trans-activation of SOM under HTs. In addition, AGL67 recruits the histone mark reader EARLY BOLTING IN SHORT DAY (EBS), which recognizes H3K4me3 at SOM chromatin. In response to HTs, AGL67 and EBS are highly enriched around the SOM promoter. The AGL67-EBS complex is also necessary for histone H4K5 acetylation, which activates SOM expression, ultimately inhibiting seed germination. Taken together, our results reveal an essential mechanism in which AGL67 cooperates with the histone mark reader EBS, which bridges the process of H3K4me3 recognition with H4K5 acetylation, thereby epigenetically activating SOM expression to suppress seed germination under HT stress.

种子发芽是一个重要的发育过程，受到环境信号的严格控制，确保在有利的条件下发芽。高温（HT）抑制种子发芽。这一过程称为热抑制，是通过激活脱落酸并抑制赤霉酸生物合成来实现的。锌指蛋白 SOMNUS (SOM) 通过改变赤霉酸/脱落酸代谢参与种子萌发的热抑制，但其潜在的调节机制尚不清楚。在这项研究中，我们报道了拟南芥中 SOM 与其自身启动子结合并激活其自身表达，并根据其能力鉴定出 MADS-box 转录因子 AGAMOUS-LIKE67 ( AGL67 ) 作为 SOM 功能的关键参与者。识别SOM启动子内的 CArG 盒并介导 HT 下SOM的反式激活。此外，AGL67 还招募了组蛋白标记阅读器 EARLY BOLTING IN SHORT DAY (EBS)，它可识别SOM染色质上的 H3K4me3。为了响应 HT，AGL67 和 EBS 在SOM启动子周围高度富集。 AGL67-EBS 复合物对于组蛋白 H4K5 乙酰化也是必需的，组蛋白 H4K5 乙酰化会激活SOM表达，最终抑制种子萌发。综上所述，我们的结果揭示了 AGL67 与组蛋白标记读取器 EBS 合作的基本机制，它将 H3K4me3 识别与 H4K5 乙酰化过程联系起来，从而表观遗传激活SOM表达，抑制 HT 胁迫下的种子萌发。