Interaction between the enzymes of central carbon metabolism and anthocyanin biosynthesis during grape berry development

Abstract

Primary and secondary metabolites are major components of grape quality and wine typicity. Their accumulation is interconnected through a complex metabolic network, which is still not well understood. This study aims to investigate how the enzymes of central carbon metabolism interact with anthocyanin biosynthesis during grape berry development: does the accumulation of anthocyanins, which represents a non-negligible diversion of carbon metabolic fluxes, require reprogramming of central enzymes or is it controlled downstream of central metabolism? To this end, 23 enzymes involved in central carbon metabolism pathways have been analyzed in the berries of 3 grape cultivars, which have close genetic background but distinct temporal dynamics of anthocyanin accumulation. The 3 cultivars are 1) cv. Gamay, which has white flesh over berry development; 2) cv. Gamay de Bouze, which is a somatic mutant of cv. Gamay with white flesh at beginning of berry development and starts to accumulate anthocyanins in the flesh at the onset of fruit ripening; 3) cv. Gamay Fréaux, which is a somatic mutant of cv. Gamay de Bouze with flesh accumulating anthocyanins as early as fruit set. The temporal differences of anthocyanin accumulation of the three cultivars make them a valuable model system to study the interaction between primary and secondary metabolisms in grape berry. Berries of the three cultivars have been sampled at 11 times from fruit set to maturity. Primary metabolites (sugars, organic acids, and 21 free amino acids) and anthocyains have been analyzed, in conjunction with qPCR analysis of key genes involved in anthocyanin biosynthesis. The results showed that hexose concentrations are the same in the fleshes of the three cultivars; however, phenylalanine is much lower in the genotype that accumulates more anthocyanins. The expression of key genes involved in the anthocyanin biosynthesis pathway is in line with anthocyanin accumulation in each cultivar. Enzyme activity analysis also showed that enzymes involved in glycolysis (PGI, PGM) were highest in cv. Gamay Fréaux，and lowest in Gamay, in the same order as anthocyanin concentration. These results provide clues to modulate the balance between primary and secondary metabolites in grape berry. Acknowledgement: This work is partly supported by a grant from FR BIE “Biologie Intégrative et Ecologie” at Bordeaux University to ZD and YG.