Profiling the Hydrolysis of Isolated Grape Berry Skin Cell Walls by Purified Enzymes

The unraveling of crushed grapes by maceration enzymes during winemaking is difficult to study because of the complex and rather undefined nature of both the substrate and the enzyme preparations. In this study we simplified both the substrate, by using isolated grape skin cell walls, and the enzyme preparations, by using purified enzymes in buffered conditions, to carefully follow the impact of the individual and combined enzymes on the grape skin cell walls. By using cell wall profiling techniques we could monitor the compositional changes in the grape cell wall polymers due to enzyme activity. Extensive enzymatic hydrolysis, achieved with a preparation of pectinases or pectinases combined with cellulase or hemicellulase enzymes, completely removed or drastically reduced levels of pectin polymers, whereas less extensive hydrolysis only opened up the cell wall structure and allowed extraction of polymers from within the cell wall layers. Synergistic enzyme activity was detectable as well as indications of specific cell wall polymer associations

Following the Compositional Changes of Fresh Grape Skin Cell Walls during the Fermentation Process in the Presence and Absence of Maceration Enzymes

Cell wall profiling technologies were used to follow compositional changes that occurred in the skins of grape berries (from two different ripeness levels) during fermentation and enzyme maceration. Multivariate data analysis showed that the fermentation process yielded cell walls enriched in hemicellulose components because pectin was solubilized (and removed) with a reduction as well as exposure of cell wall proteins usually embedded within the cell wall structure. The addition of enzymes caused even more depectination, and the enzymes unravelled the cell walls enabling better access to, and extraction of, all cell wall polymers. Overripe grapes had cell walls that were extensively hydrolyzed and depolymerized, probably by natural grape-tissue-ripening enzymes, and this enhanced the impact that the maceration enzymes had on the cell wall monosaccharide profile. The combination of the techniques that were used is an effective direct measurement of the hydrolysis actions of maceration enzymes on the cell walls of grape berry skin

BLUPS correlations.

<p>BLUPS correlations.</p

Manhattan plots from GWAS results.

<p>GWA scan results for A) GYLD 2009; B) GYLD 2010; C) LM6 2009; D) LM6 2010. The blue horizontal line in each plot represents the arbitrary significant threshold at -log10 (p value) = 3.</p

GWAS results.

<p>GWAS results.</p

Descriptive statistics for field trials.

<p>Descriptive statistics for field trials.</p

Population structure analysis.

<p>Scores plot of PC1 vs. PC2 from PCA on the markers analyzed. Blue and yellow colors correspond to 6-row and 2-row groups respectively as assigned based on results from STRUCTURE. Branches and closed circles in black color correspond to genotypes not uniquely assigned to a group.</p

Average intra-chromosomal LD decay.

<p>r² values of LD are plotted as a function of the distance between pairs of markers considered. Black line: r² values of the 95^th percentile for unlinked (>50 cM) markers. Red line: second degree smoothed loess curve.</p