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 growing season. In this study, we identify a fate switch comprised of the MKK3–MPK7 kinase cascade and the ethylene response factor ERF4 that is responsible for the seed state transition from dormancy to germination. We show that dormancy-breaking factors activate the MKK3–MPK7 module, which affects the expression of some α-EXPANSIN (EXPA) genes to control seed dormancy. Furthermore, we identify a direct downstream substrate of this module, ERF4, which suppresses the expression of these EXPA s by directly binding to the GCC boxes in their exon regions. The activated MKK3–MPK7 module phosphorylates ERF4, leading to its rapid degradation and thereby releasing its inhibitory effect on the expression of these EXPA s. Collectively, our work identifies a signaling chain consisting of protein phosphorylation, degradation, and gene transcription , by which the germination promoters within the embryo sense and are activated by germination signals from ambient conditions. This study shows that the MKK3–MPK7 cascade positively regulates dormancy breaking by promoting the expression of some EXPA s, whereas ERF4 binds directly to the GCC boxes in the exons of EXPA s and suppresses their expression. During the dormancy-breaking process, the activated MKK3–MPK7 cascade phosphorylates ERF4 and promotes its rapid degradation, leading to release of its inhibitory effect on EXPA expression. [ABSTRACT FROM AUTHOR]