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Abstract:
Background: Grapes (Vitis species) are economically the most important
fruit crop worldwide. However, the complexity of molecular and
biochemical events that lead to ripening of berries as well as how aroma
is developed are not fully understood.
Methodology/Principal Findings: In an attempt to identify the common
mechanisms associated with the onset of ripening independently of the
cultivar, grapes of Portuguese elite cultivars, Trincadeira, Aragones,
and Touriga Nacional, were studied. The mRNA expression profiles
corresponding to veraison (EL35) and mature berries (EL36) were
compared. Across the three varieties, 9,8% (2255) probesets
corresponding to 1915 unigenes were robustly differentially expressed at
EL 36 compared to EL 35. Eleven functional categories were represented
in this differential gene set. Information on gene expression related to
primary and secondary metabolism was verified by RT-qPCR analysis of
selected candidate genes at four developmental stages (EL32, EL35, EL36
and EL 38). Gene expression data were integrated with metabolic
profiling data from GC-EI-TOF/MS and headspace GC-EI-MS platforms.
Conclusions/Significance: Putative molecular and metabolic markers of
grape pre-ripening and ripening related to primary and secondary
metabolism were established and revealed a substantial developmental
reprogramming of cellular metabolism. Altogether the results provide
valuable new information on the main metabolic events leading to grape
ripening. Furthermore, we provide first hints about how the development
of a cultivar specific aroma is controlled at transcriptional level.
