iTRAQ-Based Quantitative Proteomics of Developing and Ripening Muscadine Grape Berry

Grapes
are among the widely cultivated fruit crops in the world. Grape berries
like other nonclimacteric fruits undergo a complex set of dynamic,
physical, physiological, and biochemical changes during ripening.
Muscadine grapes are widely cultivated in the southern United States
for fresh fruit and wine. To date, changes in the metabolites composition
of muscadine grapes have been well documented; however, the molecular
changes during berry development and ripening are not fully known.
The aim of this study was to investigate changes in the berry proteome
during ripening in muscadine grape cv. Noble. Isobaric tags for relative
and absolute quantification (iTRAQ) MS/MS was used to detect statistically
significant changes in the berry proteome. A total of 674 proteins
were detected, and 76 were differentially expressed across four time
points in muscadine berry. Proteins obtained were further analyzed
to provide information about its potential functions during ripening.
Several proteins involved in abiotic and biotic stimuli and sucrose
and hexose metabolism were upregulated during berry ripening. Quantitative
real-time PCR analysis validated the protein expression results for
nine proteins. Identification of vicilin-like antimicrobial peptides
indicates additional disease tolerance proteins are present in muscadines
for berry protection during ripening. The results provide new information
for characterization and understanding muscadine berry proteome and
grape ripening.