Integrating mitoflash, energy substrate, and hormone analyses to advance understanding of Magnolia endodormancy...

Flower bud dormancy ensures trees can survive winter and successfully flower and reproduce in early spring, yet its activation mechanism remains elusive. In this study, four dormancy stages of the Magnolia flower buds were identified via a multidimensional analysis. Mitochondrial flash (mitoflash) increased during floral bud endodormancy release, and this redox signal aligns with the dynamics of ROS compounds and the expression of antioxidant-related genes, which is expected to be a physiological signal for dormancy release. At this stage, mitochondrial energy resources depend on the oxidation of pyruvate and fatty acids. In addition, transcriptome analysis showed that genes related to sugar metabolism were mostly upregulated, and targeted lipidome analysis showed significant upregulation of metabolites related to fatty acid degradation and linoleic acid metabolism at the endodormancy-release stage, confirming that energy supply and metabolism increase at this period. Moreover, hormone content dynamics showed an opposite trend between active GA and ABA from dormancy to release. The expression of MdMYB91 is upregulated following ABA application, and it directly binds to the promoter of protein phosphatase type 2C (MdPP2C37-like) to negatively regulate its expression, which positions MdMYB91 as a promising regulator of dormancy by affecting ABA signaling.