Somatic embryogenesis (SE) represents a central regeneration system for the implementation of new breeding technologies in grapevine (
Vitis
spp.). However, its practical use remains constrained by genotype dependence, prolonged developmental timelines, and variability associated with explant type and culture conditions. This study evaluated SE and embryo-to-plant conversion across fifteen recalcitrant European genotypes and hybrids from Italy, Spain, Portugal, and Hungary using anthers and ovaries cultured on three induction media, followed by embryo germination. Ovaries generally exhibited higher responsiveness to SE than anthers, the PIV medium showed the broadest effectiveness, although the genotype was the primary determinant of the SE process. Noteworthy, differences in embryogenesis competence did also emerge among clones of Nebbiolo cultivar highlighting intra-cultivar variability effects. By extending the duration of callus culture beyond the conventional evaluation windows and using a two-media induction protocol, the embryogenesis success increased in several genotypes, suggesting that premature callus elimination may underestimate SE potential. Regeneration experiments confirmed that the embryo-to-plant transition was the second critical step of the process. For instance, Kadarka was a cultivar with low aptitude to SE and high regeneration efficiency, whereas other genotypes displayed poor embryo germination. Overall, all fifteen recalcitrant grapevine genotypes produced SE although plant regeneration was not achieved in Graciano and Fernão Pires. The results support a two-bottleneck-based model of grapevine regeneration controlled by genotype. Inefficiencies in the embryo-to-plant conversion constitute a highly limiting factor for downstream plant breeding applications, underscoring the need for genotype-specific optimization strategies able to address both embryogenic induction and regeneration efficiency.
A. Moine, M. Nicotera, Giorgia Sportelli et al.· Journal of Plant Growth Regu...· 0 citations
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. 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. 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.
