论文题目：The N 6-methyladenosine reader ECT1 regulates seed germination via gibberellic acid- and phytochrome B-mediated signaling
论文作者：Zenglin Li, Yuhang Ma, Wen Sun, Pengjun Ding, Yifan Bu, Yuhong Qi, TingruiShi,Chengchao Jia, Beilei Lei, and Chuang Ma
论文摘要：Seed germination, a pivotal stage in plant growth, is governed by phytohormones such as gibberellic acid (GA) and influenced by phytochromes, which are key photoreceptors in plants. The N 6-methyladenosine (m6A) RNA modification is fundamental to plant growth and development. However, the molecular mechanisms underlying the regulation of PHYTOCHROME B (phyB) and the function of m6A signaling in GA-mediated seed germination remain elusive. Here, we discovered EVOLUTIONARILY CONSERVED C-TERMINAL REGION 1 (ECT1) as an m6A reader protein that directly binds to m6A and forms homodimers to enhance its stability in Arabidopsis ( Arabidopsis thaliana ). We observed that the ect1-1 mutant exhibits attenuated GA3 responsiveness in seed germination. Restoration of ECT1 function in ect1-1 confirmed the role of ECT1 in promoting seed germination. Our findings indicate that ECT1 promotes seed germination by destabilizing m6A-modified REPRESSOR OF GA1-3 1 ( RGA1 ), a key inhibitor of GA-mediated seed germination. Moreover, ECT1 establishes a regulatory circuit with DOF AFFECTING GERMINATION 2 (DAG2), another regulator of GAmediated seed germination. DAG2 directly binds to the ECT1 promoter and controls its transcription, and ECT1 modulates DAG2 mRNA stability through m6A binding. Furthermore, we identified PHYB as a common downstream target of DAG2 and ECT1. ECT1 binds directly to m6A-modified PHYB and influences its stability, and DAG2 binds to the PHYB promoter to regulate its transcription. Our findings demonstrate that ECT1 fine-tunes m6A-regulated seed germination via complex and multifaceted molecular mechanisms, particularly through interactions with GA and phyB, broadening our understanding of m6A-regulated processes in Arabidopsis.
种子萌发是植物生长的关键阶段，受赤霉素（GA）等植物激素调控，并受植物关键光受体光敏色素的影响。 N 6-甲基腺苷（m6A）RNA修饰对植物生长发育具有重要作用。然而，光敏色素B（phyB）的调控机制以及m6A信号在GA介导的种子萌发中的功能仍不清楚。本研究发现，拟南芥中的m6A阅读蛋白EVOLUTIONARILY CONSERVED C-TERMINAL REGION 1（ECT1）能直接结合m6A修饰，并可通过形成同源二聚体增强自身稳定性。遗传分析表明， ect1-1 突变体在种子萌发过程中对GA3的响应显著减弱，而回补实验证实ECT1具有促进种子萌发的功能。分子机制研究发现，ECT1通过促进GA信号关键抑制因子 RGA1 （ REPRESSOR OF GA1-3 1 ）的m6A修饰依赖性降解来解除其对种子萌发的抑制作用。此外，ECT1与另一GA调控因子DAG2（DOF AFFECTING GERMINATION 2）形成双向调控回路：DAG2直接结合 ECT1 启动子调控其转录，而ECT1通过m6A结合调控 DAG2 mRNA的稳定性。进一步研究发现， PHYB 是DAG2和ECT1的共同下游靶标—ECT1通过结合 PHYB mRNA的m6A修饰调控其稳定性，而DAG2通过结合 PHYB 启动子调控其转录。本研究揭示了ECT1通过多层次分子机制（特别是与GA和phyB信号的互作）精细调控m6A介导的种子萌发过程，拓展了拟南芥中m6A调控网络的认知。
论文链接： https://doi.org/10.1093/plphys/kiaf180