The m ⁶ A Reader ECT1 Mediates Seed Germination via the DAG2-ECT1-PHYB Regulatory Cascade in Arabidopsis

The N ⁶ -methyladenosine (m ⁶ A) RNA modification, a significant epitranscriptomic mark, is integral to plant growth and development. m ⁶ A reader proteins are capable of recognizing m ⁶ A modifications to impact RNA metabolic and biological processes. Here, we discovered ECT1 as an m ⁶ A reader protein that directly binds to the m ⁶ A site and plays a role in positively regulating seed germination in the context of gibberellins (GAs). ECT1 undergoes m ⁶ A 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 the ECT1 promoter to control its transcription. ECT1 modulates the mRNA stability of DAG2 . Furthermore, we identified PHYB , 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 of PHYB at the transcriptional and post-transcriptional levels, respectively. ECT1 binds directly to PHYB , thereby influencing its stability. While DAG2 binds to the PHYB promoter to regulate its transcription. Together, these results unveil that ECT1 participates in the m ⁶ A signaling pathway through complex and multifaceted molecular mechanisms, broadening the spectrum of m ⁶ A reader functions and deepening our insight into the m ⁶ A signaling network in Arabidopsis .