VvERF045 Integrates Ethylene, Brassinosteroid and Abscisic Acid Pathways to Orchestrate Anthocyanin Biosynthesis in Grapevine

Anthocyanin biosynthesis in non-climacteric grape berries is regulated through coordinated phytohormonal signalling networks. However, the precise mechanisms by which abscisic acid (ABA), brassinosteroids (BRs) and ethylene (ET) synergistically modulate this process remain unclear. In this study, we identified the ET-responsive transcription factor VvERF045 as a critical integrator mediating the crosstalk among ET, BR and ABA pathways, thereby regulating anthocyanin biosynthesis. Mechanistically, VvERF045 physically interacts with its R2R3-MYB partner, VvMYB62, to co-activate the structural genes (SGs) involved in anthocyanin, BR and ABA biosynthesis pathways, including VvUFGT, VvDFR, VvDWF4, VvCPD, VvZEP/ABA1, thus collaboratively redirecting metabolic resources toward the production of anthocyanin, BR and ABA, respectively. Notably, ET significantly enhances the activity of VvERF045, suggesting a potential regulatory hierarchy wherein both BR-dependent and ABA-dependent berry pigmentation may be contingent on upstream ET perception. Collectively, our findings provide insights into how non-climacteric grape fruits temporally coordinate phytohormone pathways for colouration, revealing VvERF045 as a central regulator that bridges ET sensing to BR-mediated and ABA-mediated anthocyanin accumulation.