The MKK3–MPK7 cascade phosphorylates ERF4 and promotes its rapid degradation to release seed dormancy in Arabidopsis

Seeds establish dormancy to delay germination until the arrival of a favorable growth season. Here, we identify a fate switch constituted by the MKK3-MPK7 kinase cascade and the ethylene response factor ERF4 responsible for the seed state transition from dormancy to germination. We show that dormancy-breaking factors activate the MKK3-MPK7 module, which affects and relies on the expression of some EXPAs to control seed dormancy. Furthermore, we identify a direct downstream substrate of this module, ERF4, which suppresses the expression of these EXPAs by directly binding to the GCC boxes in their exon regions. The activated MKK3-MPK7 module phosphorylates ERF4, leading to its rapid degradation, thereby releasing its inhibitory effect on the expression of these EXPAs. Overall, our work identifies a signaling chain consisting of protein phosphorylation, degradation, and gene transcription, dependent on which the germination promoters within the embryo are sensing and activated by the germination signals from ambient conditions.