Identification and Characterization of Proteins of Enological Significance in Florida Hybrid Bunch Grape

Blanc Du Bois is a popular grape cultivar grown in Southeastern US. It is harvested at Brix between 16° and 22° depending on wine style and to avoid rain. Berry composition is a major contributing factor of wine quality and varietal characteristics. Gel-free proteome analysis was applied to characterize key metabolic pathways of proteins with enological significance. Grape (Vitis spp cv. Blanc du Bois) berries from maturing and ripening stages were collected based on Brix and acidity. Proteins extracted, electrophoresed, excised from gel as a single band, destained and subjected to proteolysis using trypsin. Trypsin digests were separated on nano LC and analyzed using LTQ Orbitrap Velos mass spectrometer. Raw files were processed using Proteome Discoverer with Sequest and Mascot search nodes using Vitis species FASTA database (70,263 entries) followed by validation with Scaffold software.  A total of 1091, 1131, 1078, 1042 and 1066 proteins were detected in green, veraison, two ripening and late ripe stages of berries, respectively. Statistical ANOVA analysis revealed 926 common proteins in all stages that are associated with various cellular processes. Comparative analysis revealed more than three-fold increase in 17 proteins (dihydroflavonol reductase, sucrose phosphate synthase and PR proteins) between ripe and late ripe stages. Other proteins including alcohol dehydrogenase 1, anthocyanidin reductase, phospho-2-dehydro-3-deoxyheptonate aldolase, hydroperoxide lyase, sucrose synthase, cinnamyl alcohol dehydrogenase, -isopiperitenol (-)-carveol and SAM-methyltransferases increased by two-folds. These data indicate that enzymes associated with sugar metabolism, flavor volatiles and polyphenol production are active till late ripening in Blanc du Bois. Supported by USDA/NIFA/CBG.