In Depth Proteome Analysis of Ripening Muscadine Grape Berry cv. Carlos Reveals Proteins Associated with Flavor and Aroma Compounds

Ripening in nonclimacteric fruits
such as grape involves complex
chemical changes that have a profound influence on the accumulation
of flavor and aroma compounds distinct to a particular grape genotype.
In this study, proteome characterization of wine type bronze muscadine
grape (Vitis rotundifolia cv. Carlos), primarily
grown in the Southeastern United States was performed during berry
ripening. Stage-specific protein expression was obtained among different
stages of berries. Differential analysis showed the expression of
522 proteins that regulate diverse biological processes and metabolic
pathways. Of these, 30 proteins are associated with the production
of key phenolic compounds, whereas 25 are associated with the production
of muscadine aroma compounds. These proteins are involved in the phenylpropanoid
pathway, terpene synthesis, fatty acid derived volatiles and esters
that affect muscadine berry flavor and aroma characteristics. Further,
gene expression analysis during ripening validated the expression
pattern of 12 proteins. Catechin, epicatechin, and four stilbenes
were quantified to correlate observed proteome changes. This study
not only revealed biochemical changes during muscadine berry ripening
but also offers indicators for marker-assisted breeding to enhance
organoleptic properties of muscadine grape to improve its flavor and
aroma properties.