EARLY BUD BREAK and SHORT VEGETATIVE PHASE 4 integrate abscisic acid (ABA) plant hormone signaling control of grape bud dormancy

1. VvSVP4 promotes dormancy by activating VvPYL9 and enhancing ABA signaling. 2. VvEBB triggers bud break by repressing VvSAPK2 and activating IAA/CK pathways. 3. Transcriptome and hormone data reveal opposing roles of VvSVP4 and VvEBB in ABA-driven dormancy and IAA/CK-mediated bud break. Bud dormancy is a crucial adaptation for perennial fruit plants, enabling them to withstand unfavorable growth conditions. This adaptive strategy plays a significant role in the survival and reproduction of these plants, yet its molecular basis is not fully understood. In the current study, two transcription factors in grapes, EARLY BUD BREAK ( VvEBB ) and SHORT VEGETATIVE PHASE 4 ( VvSVP4 ), were identified and examined. The findings demonstrated that, following heterologous transformation in poplar, VvSVP4 functions as a negative regulator, whereas VvEBB acts as a positive regulator in the process of bud-break. Transcriptome analysis showed that plant hormone signaling pathways, specifically those involving abscisic acid (ABA), indole acetic acid (IAA), and cytokinin (CK), were significantly enriched in plants overexpressing VvSVP4 ( VvSVP4oe ) and VvEBB ( VvEBBoe ), compared to control plants. Additionally, changes in the endogenous levels of ABA, IAA, and CK were found to be positively correlated with the transcriptome data. During the endodormancy phase, VvSVP4 directly and positively influenced the expression of the ABA receptor gene VvPYL9 , thereby maintaining the state of bud dormancy. Conversely, during ecodormancy, the VvEBB gene was rapidly upregulated and negatively impacted the expression of the sucrose nonfermenting 1-related protein kinase subfamily 2 gene ( VvSAPK2 ), facilitating the release from dormancy. In summary, this study offers a comprehensive explanation of the roles of VvSVP4 and VvEBB genes in dormancy and bud break, integrating insights into cell cycle regulation and multiple hormones signaling pathways.