The m⁶A Reader ECT1 Mediates Seed Germination via the DAG2-ECT1-PHYB Regulatory Cascade inArabidopsis

TheN⁶-methyladenosine (m⁶A) RNA modification, a significant epitranscriptomic mark, is integral to plant growth and development. m⁶A reader proteins are capable of recognizing m⁶A modifications to impact RNA metabolic and biological processes. Here, we discovered ECT1 as an m⁶A reader protein that directly binds to the m⁶A site and plays a role in positively regulating seed germination in the context of gibberellins (GAs). ECT1 undergoes m⁶A modification to ensure its own stability and engages in self-interaction to enhance its protein stability. Moreover, ECT1 establishes a regulatory circuit with DAG2, which has been reported to play a positive regulatory role in GA-mediated seed germination. We found that DAG2 directly binds to theECT1promoter to control its transcription. ECT1 modulates the mRNA stability ofDAG2. Furthermore, we identifiedPHYB, which encodes a key photoreceptor controlling GA-regulated seed germination, as a common downstream target of DAG2 and ECT1. DAG2 and ECT1 regulate the expression ofPHYBat the transcriptional and post-transcriptional levels, respectively. ECT1 binds directly toPHYB, thereby influencing its stability. While DAG2 binds to thePHYBpromoter to regulate its transcription. Together, these results unveil that ECT1 participates in the m⁶A signaling pathway through complex and multifaceted molecular mechanisms, broadening the spectrum of m⁶A reader functions and deepening our insight into the m⁶A signaling network inArabidopsis.