Skin proteomic comparison among four grape cultivars with different anthocyanin contents

Grape skin is characterized by a very intense metabolism during ripening involving many biosynthetic activities such as those relating to secondary compounds like the anthocyanins. In order to improve our knowledge about the physiology of this tissue, we performed a comparison among the proteomes of the ripe skin of ‘Riesling Italico’, ‘Pinot Gris’, ‘Pinot Noir’ and ‘Croatina’, genotypes that accumulate anthocyanins to different extents. In order to examine quantitative changes in proteomic maps, data underwent a two-way ANOVA test using cultivars and years as factors. The 297 significant variations underwent two different clustering procedures. By means of the two-way hierarchical clustering, it was possible to observe that the gels of the four cultivars were arranged in an order that clearly reflected anthocyanin levels and emphasized the similarities between the two Pinots, from one side, and the divergence of the proteome of ‘Croatina’, from the other. It was then possible to group the 297 spots, according to their trends, in six clusters through the k-means procedure. One of the clusters included 85 spots showing a variation profile that could be associated with anthocyanin levels. Some were identified through LC-ESI-MS/MS and their role was discussed.