Quantitative Proteome Analysis of Developing and Ripening Muscadine Grape Berry

Muscadine grapes (Vitis rotundifolia) are an economically important fruit crop in the southeastern US. Proteins play an important role in the synthesis and accumulation of various metabolites with significant enological value. To study changes in protein expression during maturation and ripening, muscadine berry cv. Noble proteome was studied by iTRAQ analysis. Proteins were extracted from berries of different maturities and ripening, and labeled with iTRAQ 8 plex reagents, followed by tandem mass spectrometry. Mass spectrometric data acquired from four replicate analyses were searched against the Uniprot Viridiplantae dataset. Based on this analysis about 650 unique proteins were identified across different maturities. The sequence annotation and GO term enrichment analysis assisted by Blast2GO tool permitted pathway analysis and determination of various biological processes and metabolic pathways that are regulated during ripening. Proteins thus identified were classified into twelve groups based on their function. These data showed that majority of proteins are linked to metabolism and protein processing. The results gave a better insight in to the changes in muscadine berry proteome during ripening and underline some important commercial traits. The data showed that in maturing berry changes in protein expression pertained mainly to carbohydrate metabolism while in ripening berry they were concerned with enzymes involved in the production of polyphenols and anthocyanins. Detailed analysis of function-related protein profiles helped discover a set of proteins that appears to play key roles in regulating enological and disease tolerance characteristics of grape berry. Supported by USDA/CBG grant.