Napa Valley Cabernet Sauvignon Proanthocyanidin Changes During Fruit Ripening: A Multi-Appellation Survey.

In 2015, an experiment was designed to investigate the distribution and variance of in winegrape flavonoids across the ripening phase in the Napa Valley. This Cabernet Sauvignon experiment was intended to evaluate the polyphenol differences across Napa Valley in order to understand parameters controlling "proanthocyanidin activity." This method has shown promise in understanding proanthocyanidin (PA) astringency based on size distribution, pigmentation, conformation, and composition. Results from whole berry partial extractions showed that seed PA material was driving PA activity early in the ripening phase, while the formation of the pigmented polymer led to a decrease later in the growing season. Multivariate analysis showed that the main drivers of changes across the ripening phase were the molecular masses of PAs and the amount of pigmentation. Given the high amount of variability seen in the experiment between sites in such a small geographical area, the results suggest that manipulation of PA activity may be possible in the vineyard, perhaps explaining variations in wine mouthfeel attributes between locations. These results can be used to develop furthermore controlled experiments targeting the variables responsible for PA activity changes.

Quantitative Proteome Analysis Reveals Changes in the Protein Landscape During Grape Berry Development With a Focus on Vacuolar Transport Proteins.

The vacuole plays a central role in fruit growth and quality formation, yet its proteomic landscape is largely unknown. In the present study, a protocol for isolating intact vacuoles from grape flesh tissue was successfully established. Quantitative proteome analysis identified 2533 proteins from five sampling dates along Cabernet Sauvignon berry development from stage I to III; among them, 1443 proteins were identified on all five sampling dates in at least two biological replicates per sample and were designated core proteome, and 1820 were recruited as differentially abundant proteins (DAPs) by sequential pairwise comparisons using arbitrary fold change of >1.5 and P < 0.05. Metabolism consistently constituted the largest category of identified proteins for both core proteome and DAPs, together with a consistently high proportion of protein-fate category proteins, indicating that the classic lytic functions of vegetative cell vacuoles are maintained throughout berry development; accumulation of metabolites involved in high sugar and other berry qualities in the late developmental stage added to the conventional lytic role of the flesh cell vacuoles. Overall increases in abundance of the DAPs were seen in the transporter proteins, membrane fusion/vesicle trafficking, and protein-fate categories, and decreased abundance was seen for DAPs in the stress, energy and cytoskeleton categories as berry development progressed. A very pronounced proteomic change was revealed between late stage I and mid stage II, with 915 increased and 114 decreased DAPs, demonstrating a significant surge of the vacuolar proteome underlying the rather static phenotypical and physiological phase. We identified 161 transport proteins with differential abundance, including proton pumps, aquaporins, sugar transporters, ATP-binding cassette transporters and ion transport proteins, together with organic compound transport proteins, the highest number and variety of berry tonoplast transporters found in grape proteome efforts to date. We further found a pre-positive increment of 96 transport proteins from the middle of stage II, before the berry undergoes its dramatic physiological changes at and following véraison. Our results are the first to describe the proteome of a vacuole-enriched preparation, toward understanding the functions of the largest compartment in berry cells during grape growth and ripening.

Transcriptomic Analyses of Root Restriction Effects on Phytohormone Content and Signal Transduction during Grape Berry Development and Ripening.

Phytohormones strongly influence growth, development and nutritional quality of agricultural products by modulating molecular and biochemical changes. The purpose of the present study was to investigate the influence of root restriction (RR) treatment on the dynamic changes of main phytohormones during the berry development and ripening of "Summer Black" early ripening seedless grape (Vitis vinifera × V. labrusca), and to analyze the changes in the biosynthesis and signal transduction pathways of phytohormones by transcriptomics. Enzyme-linked immunosorbent assay (ELISA) and Ultra Performance Liquid Chromatography-High Resolution Mass Spectrometry (UPLC-HRMS) were used to quantify the phytohormone levels, and RNA-Seq was used to analyze the transcript abundance. The results showed that 23 transcripts involved in the phytohormone biosynthesis and 34 transcripts involved in the signal transduction pathways were significantly changed by RR treatment. RR also increased abscisic acid, brassinosteroid, ethylene, jasmonic acid and salicylic acid levels, while decreasing auxin, cytokinin, and gibberellin contents. The results of the present study suggest that RR treatment can accelerate the grape ripening process, and specific candidate genes were identified for further functional analysis.