Malic acid metabolism regulation and related genes expression during berry development in Vitis heyneana cv. Yeniang No. 2

【Objective】This study aimed to analyze the dynamics of malic acid metabolism and the expression patterns of related genes during berry development in Vitis heyneana cv. Yeniang No. 2，provided reference for improving the brewing quality of V heyneana cv. Yeniang No. 2 and facilitating the production of high-quality wines.【Method】Fiveyear-old V heyneana cv. Yeniang No. 2 grapes were used as experimental materials，berries at different developmental stages were collected at 5-17 weeks after full bloom. The single berry weight，pH，soluble solids content（SSC）and titratable acidity（TA）content were measured. High-performance liquid chromatography（HPLC）was employed to determine the contents of malic acid，citrate，and tartrate in the berries. Enzyme-linked immunosorbent assay（ELISA）was used to assess the activities of key enzymes in malic acid metabolism：activities of NAD-dependent malate dehydrogenase（NAD-MDH），NADP-malic enzyme（NADP-ME）and phosphoenolpyruvate carboxylase（PEPC）. Real-time fluorescence quantitative PCR was conducted to quantify the relative expression levels of genes related to malic acid metabolism（PEPC，MDH and ME），and the correlations between these genes and malic acid content were analyzed.【Result】The single berry weight of V. heyneana cv. Yeniang No. 2 grapes increased rapidly before the veraison stage. During veraison，pH，SSC and malic acid content of the berries were as 1.03，1.36，and 2.38 times as those of 5 week after full bloom respectively. The TA peaked at 11 weeks after full bloom，reaching 35.68 mg/g. From 5 to 17 weeks after full bloom，the contents of tartrate and citrate did not change greatly，while the malic acid content fluctua-ted greatly. The activities of NAD-MDH and NADP-ME peaked at 8 weeks after full bloom，with values of 736.06 and 453.50 nmol/ （g·min）respectively，while PEPC activity was high during the early berry development stage. During veraison，the relative expression of MDH gene was as 1.62 times as that at 5 weeks after full bloom，while the relative expression levels of PEPC and ME genes were lower than that at 5 weeks after full bloom. Correlation analysis revealed extremely significant positive correlation between malic acid content and MDH gene expression（P<0.01），significant positive correlation with PEPC gene expression （P<0.05，the same below），and significant negative correlation with ME gene expression.【Conclusion】Malic acid content variation is the primary factor influencing the trend of total acidity in V. heyneana cv. Yeniang No. 2 grapes. The veraison stage marks a transition from malic acid accumulation to degradation. The expression of related genes MDH，PEPC and ME regulates malic acid content during berry development.