Influence of freezing and heating conditions on grape seed flavan-3-ol extractability, oxidation, and galloylation pattern

In cool-climate viticulture, the short growing season can influence grape seed maturation by reducing the apparent oxidation of flavan-3-ol monomers and associated increase in seed browning. A reduction in seed maturation increases the potential extraction of flavan-3-ol monomers into wine during maceration operations, heightening bitterness. Here, we carried out a 2 × 2 factorial experiment to test the ability of freezing and heating treatments to advance maturation (decrease flavan-3-ol, improve browning) of (Vitis vinifera L.) Pinot noir and Cabernet Sauvignon seeds over a 24-h incubation period. Only freezing significantly increased seed browning in both cultivars. Subsequent correlations with seed flavan-3-ol monomer concentrations suggest that freezing enhanced the oxidation of these compounds. Interestingly, natural ripening and freezing reduced galloylated flavan-3-ol monomers to a greater extent than non-galloylated ones. This study provides new information regarding the susceptibility of flavan-3-ol monomers to freezing and heating, and also suggests that freezing can advance the maturation the seeds of under-ripe red vinifera grapes

Transcriptome and metabolite profiling reveals that prolonged drought modulates the phenylpropanoid and terpenoid pathway in white grapes (Vitis vinifera L.)

Background: Secondary metabolism contributes to the adaptation of a plant to its environment. In wine grapes, fruit secondary metabolism largely determines wine quality. Climate change is predicted to exacerbate drought events in several viticultural areas, potentially affecting the wine quality. In red grapes, water deficit modulates flavonoid accumulation, leading to major quantitative and compositional changes in the profile of the anthocyanin pigments; in white grapes, the effect of water deficit on secondary metabolism is still largely unknown Results: In this study we investigated the impact of water deficit on the secondary metabolism of white grapes using a large scale metabolite and transcript profiling approach in a season characterized by prolonged drought. Irrigated grapevines were compared to non-irrigated grapevines that suffered from water deficit from early stages of berry development to harvest. A large effect of water deficit on fruit secondary metabolism was observed. Increased concentrations of phenylpropanoids, monoterpenes, and tocopherols were detected, while carotenoid and flavonoid accumulations were differentially modulated by water deficit according to the berry developmental stage. The RNA- sequencing analysis carried out on berries collected at three developmental stages—before, at the onset, and at late ripening—indicated that water deficit affected the expression of 4,889 genes. The Gene Ontology category secondary metabolic process was overrepresented within up-regulated genes at all the stages of fruit development considered, and within down-regulated genes before ripening. Eighteen phenylpropanoid, 16 flavonoid, 9 carotenoid, and 16 terpenoid structural genes were modulated by water deficit, indicating the transcriptional regulation of these metabolic pathways in fruit exposed to water deficit. An integrated network and promoter analyses identified a transcriptional regulatory module that encompasses terpenoid genes, transcription factors, and enriched drought- responsive elements in the promoter regions of those genes as part of the grapes response to drought Conclusion: Our study reveals that grapevine berries respond to drought by modulating several secondary metabolic pathways, and particularly, by stimulating the production of phenylpropanoids, the carotenoid zeaxanthin, and of volatile organic compounds such as monoterpenes, with potential effects on grape and wine antioxidant potential, composition, and sensory feature

Impact of leaf removal after berry set on fruit composition and bunch rot in 'Sauvignon blanc'

Leaf removal is a viticultural practice applied to improve cluster microclimate and grape composition. This practice can reduce the incidence of bunch rot but could also promote the degradation of berry methoxypyrazines, key components for the aromatic profile of 'Sauvignon blanc' wines. The influence of cluster-zone leaf removal, applied after berry set, was evaluated on 'Sauvignon blanc' grapevines grown in the Isonzo DOC region (Italy). In 2010 and 2011, yield components and fruit chemical composition were recorded from vines in which the five basal leaves of each single shoot were manually removed at the groat-sized phenological stage, and compared to untreated vines. Our results indicated that leaf removal did not influence yield or fruit composition at harvest, but significantly decreased the incidence and severity of Botrytis bunch rot, while reducing the severity of sunburn damage to the fruit. Increased sunlight cluster exposure decreased 2-methoxy-3-isobutylpyrazine (IBMP) and 3-isopropyl-2-methoxypyrazine (IPMP) concentrations in early stages of berry development, whereas at harvest no significant differences between treatments (defoliated and non-defoliated) were observed. We conclude that leaf removal performed after berry set is a pivotal viticultural management practice to cope with harvest bunch rot complex without negatively affecting fruit composition at harvest

Investigation of non-structural carbohydrates and xylem anatomy in petiole of grapevine varieties during water limitation and after re-irrigation

Water shortage (WS) during growing of Vitis vinifera L. can limit shoot growth and affect yield and fruit quality, as well as allocation of carbon reserves into perennial organs for the upcoming years. Varietal anatomical differences, such as specific mean xylem vessel diameter in petiole, are expected to influence water transport in canes facing water limitation. Several authors have also evidenced that non-structural carbohydrates (NSC) of adjacent living parenchyma are involved in the repair mechanism of embolized vessels. In this work, we evaluated NSC level and xylem anatomy in petiole of Cabernet Sauvignon and Syrah varieties, subjected to WS and subsequent water refilling in the summer of 2017. The anatomical analysis highlighted that Syrah had high frequency of classes of large vessels, and that the xylem differentiation of vascular bundles was also affected by WS. Moreover, petiole NSC content was significantly influenced by WS and recovery, supporting the hypothesis that starch mobilization was associated to an elevated concentration in soluble NSC. This effect was determinant for Cabernet Sauvignon, whose stress response seemed to be based mainly on NSC metabolism. Finally, Syrah, differently to Cabernet Sauvignon, sustained the WS-induced increase in soluble NSC of petiole also 18 h after re-watering

Colour variation in red grapevines (Vitis vinifera L.): genomic organisation, expression of flavonoid 3'-hydroxylase, flavonoid 3',5'-hydroxylase genes and related metabolite profiling of red cyanidin-/blue delphinidin-based anthocyanins in berry skin

BACKGROUND: Structural genes of the phenyl-propanoid pathway which encode flavonoid 3'- and 3',5'-hydroxylases (F3'H and F3'5'H) have long been invoked to explain the biosynthesis of cyanidin- and delphinidin-based anthocyanin pigments in the so-called red cultivars of grapevine. The relative proportion of the two types of anthocyanins is largely under genetic control and determines the colour variation among red/purple/blue berry grape varieties and their corresponding wines. RESULTS: Gene fragments of VvF3'H and VvF3'5'H, that were isolated from Vitis vinifera 'Cabernet Sauvignon' using degenerate primers designed on plant homologous genes, translated into 313 and 239 amino acid protein fragments, respectively, with up to 76% and 82% identity to plant CYP75 cytochrome P450 monooxygenases. Putative function was assigned on the basis of sequence homology, expression profiling and its correlation with metabolite accumulation at ten different ripening stages. At the onset of colour transition, transcriptional induction of VvF3'H and VvF3'5'H was temporally coordinated with the beginning of anthocyanin biosynthesis, the expression being 2-fold and 50-fold higher, respectively, in red berries versus green berries. The peak of VvF3'5'H expression was observed two weeks later concomitantly with the increase of the ratio of delphinidin-/cyanidin-derivatives. The analysis of structural genomics revealed that two copies of VvF3'H are physically linked on linkage group no. 17 and several copies of VvF3'5'H are tightly clustered and embedded into a segmental duplication on linkage group no. 6, unveiling a high complexity when compared to other plant flavonoid hydroxylase genes known so far, mostly in ornamentals. CONCLUSION: We have shown that genes encoding flavonoid 3'- and 3',5'-hydroxylases are expressed in any tissues of the grape plant that accumulate flavonoids and, particularly, in skin of ripening red berries that synthesise mostly anthocyanins. The correlation between transcript profiles and the kinetics of accumulation of red/cyanidin- and blue/delphinidin-based anthocyanins indicated that VvF3'H and VvF3'5'H expression is consistent with the chromatic evolution of ripening bunches. Local physical maps constructed around the VvF3'H and VvF3'5'H loci should help facilitate the identification of the regulatory elements of each isoform and the future manipulation of grapevine and wine colour through agronomical, environmental and biotechnological tools

Analysis of Non-Structural Carbohydrates and Xylem Anatomy of Leaf Petioles Offers New Insights in the Drought Response of Two Grapevine Cultivars

In grapevine, the anatomy of xylem conduits and the non-structural carbohydrates (NSCs) content of the associated living parenchyma are expected to influence water transport under water limitation. In fact, both NSC and xylem features play a role in plant recovery from drought stress. We evaluated these traits in petioles of Cabernet Sauvignon (CS) and Syrah (SY) cultivars during water stress (WS) and recovery. In CS, the stress response was associated to NSC consumption, supporting the hypothesis that starch mobilization is related to an increased supply of maltose and sucrose, putatively involved in drought stress responses at the xylem level. In contrast, in SY, the WS-induced increase in the latter soluble NSCs was maintained even 2 days after re-watering, suggesting a different pattern of utilization of NSC resources. Interestingly, the anatomical analysis revealed that conduits are constitutively wider in SY in well-watered (WW) plants, and that water stress led to the production of narrower conduits only in this cultivar

Multi-Omics and Integrated Network Analyses Reveal New Insights into the Systems Relationships between Metabolites, Structural Genes, and Transcriptional Regulators in Developing Grape Berries (Vitis vinifera L.) Exposed to Water Deficit

Grapes are one of the major fruit crops and they are cultivated in many dry environments. This study comprehensively characterizes the metabolic response of grape berries exposed to water deficit at different developmental stages. Increases of proline, branched-chain amino acids, phenylpropanoids, anthocyanins, and free volatile organic compounds have been previously observed in grape berries exposed to water deficit. Integrating RNA-sequencing analysis of the transcriptome with large-scale analysis of central and specialized metabolites, we reveal that these increases occur via a coordinated regulation of key structural pathway genes. Water deficit-induced up-regulation of flavonoid genes is also coordinated with the down-regulation of many stilbene synthases and a consistent decrease in stilbenoid concentration. Water deficit activated both ABA-dependent and ABA-independent signal transduction pathways by modulating the expression of several transcription factors. Gene-gene and gene-metabolite network analyses showed that water deficit-responsive transcription factors such as bZIPs, AP2/ERFs, MYBs, and NACs are implicated in the regulation of stress-responsive metabolites. Enrichment of known and novel cis-regulatory elements in the promoters of several ripening-specific/water deficit-induced modules further affirms the involvement of a transcription factor cross-talk in the berry response to water deficit. Together, our integrated approaches show that water deficit-regulated gene modules are strongly linked to key fruit-quality metabolites and multiple signal transduction pathways may be critical to achieve a balance between the regulation of the stress-response and the berry ripening program. This study constitutes an invaluable resource for future discoveries and comparative studies, in grapes and other fruits, centered on reproductive tissue metabolism under abiotic stress.This study was funded by the European Territorial Cooperation program (Sustainable viticulture and improvement of the territorial resources of the grape and wine industry), the Fondazione Edmund Mach (GMPF Program), the COST Action FA1106 Quality Fruit, Genome British Columbia (10R21188), and the Natural Sciences and Engineering Research Council of Canada (10R23082)

Impact of Leaf Removal, Applied Before and After Flowering, on Anthocyanin, Tannin, and Methoxypyrazine Concentrations in ‘Merlot’ (Vitis viniferaL.) Grapes and Wines

7siThe development and accumulation of secondary metabolites in grapes determine wine color, taste, and aroma. This study aimed to investigate the effect of leaf removal before flowering, a practice recently introduced to reduce cluster compactness and Botrytis rot, on anthocyanin, tannin, and methoxypyrazine concentrations in Merlot' grapes and wines. Leaf removal before flowering was compared with leaf removal after flowering and an untreated control. No effects on tannin and anthocyanin concentrations in grapes were observed. Both treatments reduced levels of 3-isobutyl-2-methoxypyrazine (IBMP) in the grapes and the derived wines, although the after-flowering treatment did so to a greater degree in the fruit specifically. Leaf removal before flowering can be used to reduce cluster compactness, Botrytis rot, and grape and wine IBMP concentration and to improve wine color intensity but at the expense of cluster weight and vine yield. Leaf removal after flowering accomplishes essentially the same results without loss of yield. © 2016 American Chemical Society.reservedmixedSivilotti, Paolo; Herrera, Jose Carlos; Lisjak, Klemen; Baša Česnik, Helena; Sabbatini, Paolo; Peterlunger, Enrico; Castellarin, Simone DiegoSivilotti, Paolo; Herrera, Jose Carlos; Lisjak, Klemen; Baša Česnik, Helena; Sabbatini, Paolo; Peterlunger, Enrico; Castellarin, Simone Dieg