Secondary metabolism and defense responses are differently regulated in two grapevine cultivars during ripening

Vitis vinifera Nebbiolo is one of the most important wine grape cultivars used to produce prestigious high-quality wines known throughout the world, such as Barolo and Barbaresco. Nebbiolo is a distinctive genotype characterised by medium/high vigour, long vegetative and ripening cycles, and limited berry skin colour rich in 3-hydroxylated anthocyanins. To investigate the molecular basis of these peculiarities, Nebbiolo berries (accession PRJNA477842) collected in different stages of ripening were compared with V. vinifera Barbera berries, rich in 3,5-hydroxylated anthocyanins, using transcriptomic and metabolic approaches. In two consecutive seasons, the two genotypes confirmed their characteristic anthocyanin profiles associated with a different modulation of the transcriptome during ripening. Secondary metabolism and response to stress were the functional categories modulated most differentially between Nebbiolo and Barbera. The profile rich in 3-hydroxylated anthocyanins in Nebbiolo was likely linked to a transcriptional downregulation of some key genes of anthocyanin metabolism. In addition, in Nebbiolo, the defence basal metabolism in the precocious phases of ripening was more active than in Barbera in absence of biotic attacks. Several pathogenesis related proteins, WRKY transcription factors, and stilbene synthase genes were overexpressed in Nebbiolo suggesting an interesting specific regulation of defence pathways in this genotype that deserves to be further explored.