An integrated proteomic and metabolomic approach reveals peculiar traits in the exocarp of four grape cultivars characterized by a different anthocyanin accumulation

In order to study the biochemical processes relating to secondary metabolism that occur in berry ripening, a proteomic and metabolomic comparative analysis among four vines characterized by different anthocyanin content was performed. The experiment restricted on skin tissue was conducted by using the 2-DE gels/ LCESI-MS/MS for proteomic investigation and GC-MS in Selected Ion Monitoring mode (SIM) for the metabolomic one. Linear discriminant analysis (LDA) pointed out that the cultivars were distinguishable and the order in which they were grouped mainly reflected their relative anthocyanin contents. The hierarchical clustering analysis clearly showed that in addition to proteins directly linked to anthocyanin biosynthesis also many of those relating to primary metabolism increased in abundance. As far as it concerns metabolomic analysis, only the levels of few key intermediates varied among cultivars in a way that may refer to anthocyanin content. Taken together the results showed that the process of grape ripening in the skin differs in some central metabolic traits among cultivars and that these variations could be linked to differences in secondary metabolism.