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 produceprestigious high-quality wines known throughout the world, such as Barolo and Barbaresco.'Nebbiolo' is a distinctive genotype characterized by medium/high vigor, long vegetative and ripeningcycles, and limited berry skin color rich in 30-hydroxylated anthocyanins. To investigate themolecular basis of these characteristics, 'Nebbiolo' berries collected at three different stages of ripening(berry pea size, véraison, and harvest) were compared with V. vinifera 'Barbera' berries, which arerich in 30,50-hydroxylated anthocyanins, using transcriptomic and analytical approaches. In twoconsecutive seasons, the two genotypes confirmed their characteristic anthocyanin profiles associatedwith a different modulation of their transcriptomes during ripening. Secondary metabolism andresponse to stress were the functional categories that most differentially changed between 'Nebbiolo'and 'Barbera'. The profile rich in 30-hydroxylated anthocyanins of 'Nebbiolo' was likely linked toa transcriptional downregulation of key genes of anthocyanin biosynthesis. In addition, at berrypea size, the defense metabolism was more active in 'Nebbiolo' than 'Barbera' in absence of bioticattacks. Accordingly, several pathogenesis-related proteins, WRKY transcription factors, and stilbenesynthase genes were overexpressed in 'Nebbiolo', suggesting an interesting specific regulation ofdefense pathways in this genotype that deserves to be further explored."