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

Abstract

AbstractTheN6-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.