Abscisic acid strongly promotes anthocyanin accumulation in grape cell suspensions (Vitis vinifera L. cv. ‘Gamay Fréaux’) independently of glucose concentration

BACKGROUND: Fruit metabolism is highly sensitive to environmental variations, with climate change disrupting processes that determine fruit composition and quality. In grapes, elevated temperatures increase sugar accumulation but reduce anthocyanin levels as co-occurring responses under heat stress, leading to imbalances that affect wine typicality. To explore sugar signaling and its interaction with abscisic acid (ABA) in regulating anthocyanin biosynthesis, we conducted a comprehensive transcriptomic and phenotypic analysis using a "Gamay Fréaux" (GT) cell suspension model. Treatments included ABA combined with varying glucose concentrations, glucose analogs, and hexokinase inhibitors. RESULTS: High glucose levels increased anthocyanin concentration by 13.2% compared to low glucose levels, whereas exogenous ABA induced far stronger increases of 108.4% and 94.4% under low- and high-glucose conditions, respectively, relative to ABA-free controls. Additionally, mannose contributed to sugar signaling, with sugar-induced anthocyanin accumulation dependent on hexokinase-mediated phosphorylation. Transcriptomic analysis revealed that while ABA strongly upregulated anthocyanin biosynthetic genes, the effect of glucose on these genes was modest. Notably, 3OM treatment induced upregulation of several structural genes but resulted in reduced anthocyanin accumulation, suggesting regulation primarily through post-transcriptional mechanisms and additional factors influencing post-translational control. By developing an open-source GT-transcriptome analysis tool and integrating it with anthocyanin quantification, we identified VviCIPK25 as a candidate gene whose expression correlates with anthocyanin accumulation in response ABA, and which may respond indirectly to sugar-induced phosphorylation status. CONCLUSIONS: This study provides a comprehensive transcriptomic resource for understanding anthocyanin regulation in grape cell suspensions and identifies VviCIPK25 as a candidate gene for future functional studies. Our findings also highlight the importance of post-transcriptional regulation in anthocyanin biosynthesis, as transcriptional changes do not always predict phenotypic outcomes.