Grape Berry Skin Research Articles

Characterization of lysine acetyltransferase and deacetylase genes and their roles in anthocyanin biosynthesis in grape

Lysine acetylation is pivotal in regulating growth, development, and stress responses across numerous plant species. This modification, mediated by lysine acetyltransferases (KATs) and lysine deacetylases (KDACs), is both dynamic and reversible. Despite the economic significance of grape (Vitis vinifera) as a fruit crop, comprehensive insights into its KAT and KDAC gene families remain limited. In this study, 8 VvKATs and 14 VvKDACs were identified within the grape genome. Detailed analyses of their physicochemical properties, chromosomal distribution, phylogenetic synteny, evolutionary relationships, gene structures, and conserved motifs were conducted. Promoter region analysis revealed numerous cis-regulatory elements linked to light, hormone, and stress responsiveness. Transcriptomic data indicated that VvKATs and VvKDACs display distinct expression profiles across various tissues and developmental stages. Notably, VvSRT1, VvHDA19a, and VvHDA15 expression levels correlated strongly with anthocyanin accumulation in grape. Application of the deacetylase inhibitor sirtinol resulted in berry color changes and increased anthocyanin accumulation, suggesting that enhanced anthocyanin content in sirtinol-treated grape berry skins may result from post-translational modifications of genes involved in anthocyanin biosynthesis. These findings contribute to a deeper understanding of VvKAT and VvKDAC gene structures and properties, establishing a foundation for further exploration into lysine acetylation's role in fruit quality, particularly anthocyanin biosynthesis, in grape.

Anthocyanin Accumulation in Grape Berry Skin Promoted by Endophytic Microbacterium sp. che218 Isolated from Wine Grape Shoot Xylem.

Grape berry skin coloration is a key determinant of the commercial value of red wines. Global warming caused by climate change has inhibited anthocyanin biosynthesis in berry skins, leading to poor coloration. Through two-year field experiments, the endophyte che218 isolated from grape shoot xylem promoted anthocyanin accumulation in berry skins. The che218 enhanced anthocyanin biosynthesis in grapevine cultured cells. In the 2022 growing season, applying che218 to grape bunches enhanced anthocyanin accumulation in berry skins on day 20 post-treatment. However, the anthocyanin accumulation enhancing effect of che218 became negligible at harvest. In the 2023 growing season, che218 enhanced anthocyanin accumulation in berry skins on day 15 post-treatment and at harvest (day 30 post-treatment) and also upregulated the transcription of mybA1 and UFGT, two genes that regulate anthocyanin biosynthesis in berry skins. Whole genome sequencing demonstrated that che218 is an unidentified Microbacterium species. However, it remains unknown how che218 is involved in the biosynthesis of anthocyanin in berry skins. This study provides insights into the development of an eco-friendly endophyte-mediated technique for improving grape berry skin coloration, thereby mitigating the effects of global warming on berry skin coloration.

Supplementing with monochromatic blue LED light during the day, rather than at night, increases anthocyanins in the berry skin of grapevine (Vitis vinifera L.).

Supplying monochromatic blue LED light during the day, but not at night, promotes early coloration and improves anthocyanin accumulation in the skin of grape berries. Specific light spectra, such as blue light, are known to promote the biosynthesis and accumulation of anthocyanins in fruit skins. However, research is scarce on whether supplement of blue light during different periods of one day can differ in their effect. Here, we compared the consequences of supplying blue light during the day and night on the accumulation of anthocyanins in pigmented grapevine (Vitis vinifera) berries. Two treatments of supplemented monochromatic blue light were tested, with light emitting diodes (LED) disposed close to the fruit zone, irradiating between 8:00 and 18:00 (Dayblue) or between 20:00 and 6:00 (Nightblue). Under the Dayblue treatment, berry coloration was accelerated and total anthocyanins in berry skins increased faster than the control (CK) and also when compared to the Nightblue condition. In fact, total anthocyanin content was similar between CK and Nightblue. qRT-PCR analysis indicated that Dayblue slightly improved the relative expression of the anthocyanin-structural gene UFGT and its regulator MYBA1. Instead, the expression of the light-reception and -signaling related genes CRY, HY5, HYH, and COP1 rapidly increased under Dayblue. This study provides insights into the effect of supplementing monochromatic LED blue light during the different periods of one day, on anthocyanins accumulation in the berry skin.

The Role of Environmental Factors and Plant Growth Regulators on Grapes Coloration

Grapevine is the world's commercial horticulture crop. Poor coloration of grapes is one of the problems in grape production. Climate changes could negatively affect grape quality by reducing color formation. The effect of high temperatures on anthocyanin content and composition in the main red-producing grapes would help estimate their phenotypic change and perhaps predict whether they will be able to sustain the attributes of high-quality grapes in the context of climate change. Climate changes played an important role in lack sufficient berry color especially high temperature inhibited L-phenylalanineammonialyase (PAL). L-phenylalanineammonialyase improved accumulation of anthocyanin in the skin of grape berries. Environmental factors like light, temperature and irrigation are effective in either grapes coloration or discoloration. Plant growth regulators like Brassinosteroids (BRs), Jasmonic acid (JA), Salicylic acid (SA) and Abscisic acid (ABA) are accelerating the accumulation of anthocyanin in grapes berry skin. So it is very important to know how grapes coloration, the effect of plant growth regulators and environmental factors on grapes coloration.

ВИТАМИНЫ, МИНЕРАЛЬНЫЕ И АРОМАТОБРАЗУЮЩИЕ ВЕЩЕСТВА В СТРУКТУРНЫХ ЭЛЕМЕНТАХ ЯГОДЫ ВИНОГРАДА СОРТОВ НАРМА И РКАЦИТЕЛИ

Grape berries, which contain organic substances, vitamins, amino acids, minerals, aromatic substances, have valuable taste and nutritional properties. An important source of biologically active substances are the pulp, skin and seeds of grape berries containing a significant amount of essential components. The purpose of the work is to determine the biochemical parameters: biologically active, mineral and aroma-forming substances in the structural elements of Narma and Rkatsiteli grape varieties cultivated in Dagestan. A capillary electrophoresis system was used to determine vitamins, composition and number of cations. The research was carried out on the device «Kapel 104T», RF, NPF LUMEX. The aroma-forming components in the experimental samples were identified using a gas chromatograph «Crystal 2000M» (RF). The mass concentration of antioxidants was measured on the device TSVET YAUZA 01-AA, (RF). The total amount of vitamins and vitamin-like substances in the autochthonous Narma variety was: in the pulp - 0.7123 mg/dm3 , in the skin – 3.4101 mg/dm3 and in the seeds – 3.7827 mg/dm3 . The total concentration of mineral elements in the skin of the studied grapes (Narma –33,2 mg/dm3 , Rkatsiteli – 20,8 mg/dm3 ) is higher than in the pulp and seeds. Significant total amounts of antioxidants were found in the seeds of the studied grapes: Narma – 6.71 mg/dm3 , Rkatsiteli – 8.51 mg/dm3 . High concentrations of aroma-forming substances were determined in the skin and seeds of berries of the Narma variety – 376.26 and 253.71 mg/dm3 , and in the Rkatsiteli variety the content of these compounds was 82.34 and 91.00 mg/dm3 , respectively. The research results complement the biochemical characteristics of Narma and Rkatsiteli grape varieties, which can be successfully used as raw materials in the food industry to enrich food with biologically active, mineral and aroma-forming substances.

Evaluation of Salt Stress-Induced Changes in Polyamine, Amino Acid, and Phytoalexin Profiles in Mature Fruits of Grapevine Cultivars Grown in Tunisian Oases

Salinity stress has become an increasing threat to viticulture in the Tunisian oasis, and more generally, the characterization of salinity tolerance markers can be of great interest for sustainable grape production. This study investigated some metabolic adaptations in different tissues of the ripe berries of indigenous grapevine cultivars after exposure to salt stress to identify the key traits of salt stress tolerance under oasis conditions. We especially focused on the adaptive responses occurring at the level of amino acids, polyamines, and stilbene phytoalexins in the grape berry skin, pulp, and seeds of six grapevine cultivars differing in phenotypic and ampelographic characteristics. Our data showed that amino acids accumulated strongly in the pulp and skin, while resveratrol, trans-piceid and trans-ε-viniferin, as major phytoalexins, significantly accumulated in the seeds. High salinity was also found to increase both the berry skin and pulp contents of essential amino acids such as threonine, valine, leucine, isoleucine, lysine, methionine, and phenylalanine. The amounts of stilbenes also increased under high salinity in the berry skin of all the studied cultivars. Polyamine homeostasis within the different berry tissues suggested enhanced polyamine biosynthesis rather than polyamine oxidation in response to high salinity. Our principal component analysis revealed a clear discrimination between the cultivars based on their metabolic profiles within the ripe berry tissues under high salinity.

Targeted deletion of grape retrotransposon associated with fruit skin color via CRISPR/Cas9 in Vitis labrascana 'Shine Muscat'.

Transposition of transposable elements affect expression levels, splicing and epigenetic status, and function of genes located in, or near, the inserted/excised locus. For example, in grape, presence of the Gret1 retrotransposon in the promoter region of the VvMYBA1a allele at the VvMYBA1 locus suppress the expression of the VvMYBA1 transcription factor gene for the anthocyanin biosynthesis and this transposon insertion is responsible for the green berry skin color of Vitis labrascana, 'Shine Muscat', a major grape cultivar in Japan. To prove that transposons in grape genome can be removed by genome editing, we focused on Gret1 in the VvMYBA1a allele as a target of CRISPR/Cas9 mediated transposon removal. PCR amplification and sequencing detected Gret1 eliminated cells in 19 of 45 transgenic plants. Although we have not yet confirmed any effects on grape berry skin color, we were successful in demonstrating that cleaving the long terminal repeat (LTR) present at both ends of Gret1 can efficiently eliminate the transposon.

RNA-Seq Based Transcriptomic Analysis of Bud Sport Skin Color in Grape Berries

The most common bud sport trait in grapevines is the change in color of grape berry skin, and the color of grapes is mainly developed by the composition and accumulation of anthocyanins. Many studies have shown that MYBA is a key gene regulates the initiation of bud sport color and anthocyanin synthesis in grape peels. In the current study, we used berry skins of ‘Italia’, ‘Benitaka’, ‘Muscat of Alexandria’, ‘Flame Muscat’, ‘Rosario Bianco’, ‘Rosario Rosso’, and ‘Red Rosario’ at the véraison stage (10 weeks post-flowering and 11 weeks post-flowering) as research materials. The relative expressions of genes related to grape berry bud sport skin color were evaluated utilizing RNA-Seq technology. The results revealed that the expressions of the VvMYBA1/A2 gene in the three red grape varieties at the véraison stage were higher than in the three white grape varieties. The VvMYBA1/A2 gene is known to be associated with UFGT in the anthocyanin synthesis pathway. According to the results, VvMYBA1/A2 gene expression could also be associated with the expression of LDOX. In addition, a single gene (gene ID: Vitvi19g01871) displayed the highest expressions in all the samples at the véraison stage for the six varieties. The expression of this gene was much higher in the three green varieties compared to the three red ones. GO molecular function annotation identified it as a putative metallothionein-like protein with the ability to regulate the binding of copper ions to zinc ions and the role of maintaining the internal stable state of copper ions at the cellular level. High expression levels of this screened gene may play an important role in bud sport color of grape berry skin at the véraison stage.

Biosynthesis of Chlorophyll and Other Isoprenoids in the Plastid of Red Grape Berry Skins.

Despite current knowledge showing that fruits like tomato and grape berries accumulate different components of the light reactions and Calvin cycle, the role of green tissues in fruits is not yet fully understood. In mature tomato fruits, chlorophylls are degraded and replaced by carotenoids through the conversion of chloroplasts in chromoplasts, while in red grape berries, chloroplasts persist at maturity and chlorophylls are masked by anthocyanins. To study isoprenoid and lipid metabolism in grape skin chloroplasts, metabolites of enriched organelle fractions were analyzed by high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) and the expression of key genes was evaluated by real-time polymerase chain reaction (PCR) in berry skins and leaves. Overall, the results indicated that chloroplasts of the grape berry skins, as with leaf chloroplasts, share conserved mechanisms of synthesis (and degradation) of important components of the photosynthetic machinery. Some of these components, such as chlorophylls and their precursors, and catabolites, carotenoids, quinones, and lipids have important roles in grape and wine sensory characteristics.

Transcriptome and metabolome reveal the effects of three canopy types on the flavonoids and phenolic acids in ‘Merlot’ (Vitis vinifera L.) berry pericarp

The flavonoids and phenolic acids in grape berries greatly influence the quality of wine. Various methods are used to shape and prune grapevines, but their effects on the flavonoids and phenolic acids remain unclear. The flavonoids and phenolic acids in the berry pericarps from grapevines pruned using three types of leaf canopy, namely, V-shaped, T-shaped, and vertical shoot-positioned (VSP) canopies, were compared in this study. Results showed that the V-shaped canopy was more favorable for the accumulation of flavonoids and phenolic acids. Transcriptome and metabolome analyses revealed that the differentially expressed genes (DEGs) and differentially regulated metabolites (DRMs) were significantly enriched in the flavonoid and phenylpropanoid biosynthesis pathways. A total of 96 flavonoids and 32 phenolic acids were detected among the DRMs. Their contents were higher in the V-shaped canopy than in the T-shaped and VSP canopies. Conjoint analysis of transcriptome and metabolome showed that nine DEGs (e.g., cytochrome P450 98A9 and 98A2) were significantly correlated to nine phenolic acids (e.g., gentisic acid and neochlorogenic acid) and three genes (i.e., chalcone isomerase, UDP-glycosyltransferase 88A1, and caffeoyl-CoA O-methyltransferase) significantly correlated to 15 flavonoids (e.g., baimaside and tricin-7-O-rutinoside). These genes may be involved in the regulation of various flavonoids and phenolic acids in grape berries, but their functions need validation. This study provides novel insights into the effects of leaf canopy on flavonoids and phenolic acids in the skin of grape berries and reveals the potential regulatory networks involved in this phenomenon.

A proteomic analysis shows the stimulation of light reactions and inhibition of the Calvin cycle in the skin chloroplasts of ripe red grape berries.

The role of photosynthesis in fruits still challenges scientists. This is especially true in the case of mature grape berries of red varieties lined by an anthocyanin-enriched exocarp (skin) almost impermeable to gases. Although chlorophylls are degraded and replaced by carotenoids in several fruits, available evidence suggests that they may persist in red grapes at maturity. In the present study, chloroplasts were isolated from the skin of red grape berries (cv. Vinhão) to measure chlorophyll levels and the organelle proteome. The results showed that chloroplasts (and chlorophylls) are maintained in ripe berries masked by anthocyanin accumulation and that the proteome of chloroplasts from green and mature berries is distinct. Several proteins of the light reactions significantly accumulated in chloroplasts at the mature stage including those of light-harvesting complexes of photosystems I (PSI) and II (PSII), redox chain, and ATP synthase, while chloroplasts at the green stage accumulated more proteins involved in the Calvin cycle and the biosynthesis of amino acids, including precursors of secondary metabolism. Taken together, results suggest that although chloroplasts are more involved in biosynthetic reactions in green berries, at the mature stage, they may provide ATP for cell maintenance and metabolism or even O2 to feed the respiratory demand of inner tissues.

Constitutive expression of VviNAC17 transcription factor significantly induces the synthesis of flavonoids and other phenolics in transgenic grape berry cells.

VviNAC17 is a grapevine transcription factor activated by ABA. Because ABA has been proposed as the main signal modulating the secondary metabolism in grape berry skins, here we postulated VviNAC17 as a positive regulator of secondary metabolism in grape cells. To validate the hypothesis, VviNAC17 was constitutively and stably overexpressed in grape berry suspension-cultured cells of Gamay Fréaux cv. by Agrobacterium-mediated transformation. Targeted transcriptional analyses by qPCR showed that several genes involved the phenylpropanoid (VviPAL1), stilbenoid (VviSTS1) and flavonoid pathways (VviDFR, VviLAR1, VviANR, VviLDOX, and VviUFGT1), as well as anthocyanin vacuolar transport and accumulation (VviGST4 and VvMATE1) were significantly upregulated in VviNAC17-overexpressing transgenic cells, which translated in the stimulation of a number of enzymatic activities in those pathways. This was the case of phenylalanine ammonia lyase (PAL) and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) that were about 2-fold and 3.5-fold higher in VviNAC17-overexpressing cells than in control cells. VviNAC17-overexpressing cells accumulated significantly higher amounts of anthocyanins, proanthocyanidins, total flavonoids and total phenolics. These findings confirmed that VviNAC17 is an important positive regulator of secondary metabolism in grapevine contributing to the accumulation of important berry quality-related secondary metabolites.

Simulation of light interaction with seedless grapes.

Spectroscopic techniques are widely used for the non-destructive maturation and quality monitoring of different fruits. To develop new sensor devices for this purpose, knowing the optical properties of the agricultural sample is crucial for enabling the prediction of the interaction of the incident light with the fruit. In the present study, the optical properties of three different seedless grape varieties (ARRA15, Tawny and Melody/Blagratwo) were determined from 400 to 1000 nm using a UV-visible/near-infrared spectrometer with an integrating sphere and subsequent calculation of the absorption and scattering coefficients and the anisotropy factor using the inverse adding doubling method. The results indicate that the optical properties of different grape varieties have significant differences, especially in the visible wavelength region, whereas these are less distinct in the near-infrared range. Independent of grape variety, the grape berry skin has a higher scattering coefficient and scattering occurs predominantly in the forward direction. Based on the optical properties of the grape berries, a three-dimensional grape berry model is generated within OpticStudio (Zemax, LLC) for the different varieties that can be used in optical illumination simulations. The bulk scattering inside the fruit is modeled by the Henyey-Greenstein distribution. A comparison of the simulated values for the total transmission and the specular reflection determined experimentally shows that realistic optical grape models can be created within OpticStudio. Overall, the procedure for creating optical grape models presented here will be helpful for the development of optical applications used in pre- and post-harvest food quality monitoring. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Genome-Wide Analysis of Multidrug and Toxic Compound Extruction Transporters in Grape.

Grape (Vitis vinifera L.) is an important fruit crop in the world. It is used as a table grape and is also used for raisin and wine production. Grape berries accumulate secondary metabolites, such as anthocyanins, tannins, and resveratrol, which are known as functional compounds for human health. Multidrug and toxic compound extrusion transporter (MATEs) transport secondary metabolites. MATEs also transport other solutes, including organic acids, and toxic xenobiotics, depending on cation gradient and play various roles in plants. MATE comprises 300–500 amino acid residues and possesses a MATE domain and 8–12 transmembrane domains. In the present study, 59 MATE genes were identified in the grape genome, and phylogenetic analysis revealed the presence of four groups of grape MATEs (Group 1–4). Their information, such as gene structures, protein motifs, predicted subcellular localizations, and gene IDs of four genome annotations, that is, CRIBI v1, CRIBI v2, Genoscope, and Vcost v3, were annotated. The transport substrates and physiological functions of grape MATEs were estimated based on their homology with the analyzed MATEs in other plant species. Group 1 may transport toxic compounds and alkaloids, Group 2 may transport polyphenolic compounds, Group 3 may transport organic acids, and Group 4 may transport plant hormones related to signal transduction. In addition to the known anthocyanin transporters, VvMATE37 and VvMATE39, a novel anthocyanin transporter, VvMATE38 in Group 2, was suggested as a key transporter for anthocyanin accumulation in grape berry skin. VvMATE46, VvMATE47, and VvMATE49 in Group 3 may contribute to Al3+ detoxification and Fe2+/Fe3+ translocation via organic acid transport. This study provides helpful and fundamental information for grape MATE studies and resolves the confusion of gene IDs in different genome annotations.

Geraniol as a Potential Stimulant for Improving Anthocyanin Accumulation in Grape Berry Skin through ABA Membrane Transport.

Climate change, particularly warmer temperature, has resulted in reduced anthocyanin accumulation in grape berry skin. Because anthocyanin is a crucial determinant of red wine quality, viticulturists need to devise a solution for mitigating the poor coloration of red/black grape berry skin under elevated temperature conditions. In this study, we investigated the effects of geraniol on anthocyanin accumulation in grape berry skins of field-grown grapevines and elucidated the molecular mechanisms of the geraniol-triggered anthocyanin accumulation. Geraniol-treated bunches showed enhanced anthocyanin accumulation in berry skins at harvest (50 days after treatment). Geraniol treatment upregulated the transcription of MybA1 and UFGT, which encode the key factors in anthocyanin biosynthesis, in berry skins. Geraniol treatment also improved anthocyanin accumulation in grape cultured cells. We isolated grape ATP-binding cassette transporter G family protein VvABCG40, encoding abscisic acid (ABA) membrane transporter, from geraniol-treated grape cultured cells. VvABCG40 transcription was upregulated in berry skins 40 days after treatment. Geraniol treatment also upregulated the transcription of VvPP2C24, which encodes ABA-responsible type 2C protein phosphatases, in berry skins, but not the transcription of VvNCED1, which encodes a key enzyme in ABA biosynthesis. Taken together, geraniol-triggered anthocyanin accumulation in berry skins is promoted by ABA membrane transport and not by ABA biosynthesis, and geraniol treatment of field-grown grape bunches may contribute to alleviating the poor coloration of berry skin as a novel technique in viticulture.

A role for ascorbate conjugates of (+)-catechin in proanthocyanidin polymerization

Proanthocyanidins (PAs) are natural polymers of flavan-3-ols, commonly (+)-catechin and (−)-epicatechin. However, exactly how PA oligomerization proceeds is poorly understood. Here we show, both biochemically and genetically, that ascorbate (AsA) is an alternative “starter unit” to flavan-3-ol monomers for leucocyanidin-derived (+)-catechin subunit extension in the Arabidopsis thaliana anthocyanidin synthase (ans) mutant. These (catechin)n:ascorbate conjugates (AsA-[C]n) also accumulate throughout the phase of active PA biosynthesis in wild-type grape flowers, berry skins and seeds. In the presence of (−)-epicatechin, AsA-[C]n can further provide monomeric or oligomeric PA extension units for non-enzymatic polymerization in vitro, and their role in vivo is inferred from analysis of relative metabolite levels in both Arabidopsis and grape. Our findings advance the knowledge of (+)-catechin-type PA extension and indicate that PA oligomerization does not necessarily proceed by sequential addition of a single extension unit. AsA-[C]n defines a new type of PA intermediate which we term “sub-PAs”.

Grafting with rootstocks promotes phenolic compound accumulation in grape berry skin during development based on integrative multi-omics analysis.

In viticulture, grafting has been practiced widely and influences grape development as well as berry and wine quality. However, there is limited understanding of the effects of rootstocks on grape phenolic compounds, which are located primarily in the berry skin and contribute to certain sensory attributes of wine. In this study, scion–rootstock interactions were investigated at the green-berry stage and the veraison stage when grapevines were hetero-grafted with three commonly used rootstock genotypes (5BB, 101-14MG, and SO4). Physiological investigations showed that hetero-grafts, especially CS/5BB, contained higher concentrations of total proanthocyanidins (PAs) and various PA components in berry skins compared with the auto-grafted grapevines. Further metabolomics analysis identified 105 differentially accumulated flavonoid compounds, the majority of which, including anthocyanins, PAs, and flavonols, were significantly increased in the berry skins of hetero-grafted grapevines compared with auto-grafted controls. In addition, transcriptomic analysis of the same samples identified several thousand differentially expressed genes between hetero-grafted and auto-grafted vines. The three rootstocks not only increased the transcript levels of stilbene, anthocyanin, PA, and flavonol synthesis genes but also affected the expression of numerous transcription factor genes. Taken together, our results suggest that hetero-grafting can promote phenolic compound accumulation in grape berry skin during development. These findings provide new insights for improving the application value of grafting by enhancing the accumulation of nutritious phenolic components in grape.

Changes in Major Phenolic Compounds of Seeds, Skins, and Pulps from Various Vitis spp. and the Effect of Powdery and Downy Mildew Diseases on Their Levels in Grape Leaves.

The main purpose of this study is to determine the contents of 3 major phenolic compounds (gallic acid, catechin, and epicatechin) in 22 different grape cultivars/hybrids obtained from 2 different breeding programs. Additionally, changes in these phenolic components in the grape leaves of some resistant/tolerant species were determined in relation to powdery and downy mildew diseases in viticulture. The skin, pulp, and seeds of grape berries were analysed over two years, while changes in the phenolic contents of grape leaves were determined before and after these diseases for two years. The major phenolic contents of new hybrids/cultivars were compared with those of popular cultivars in different parts of the grapes, and significant differences in phenolic contents were found among hybrids/cultivars and different grape parts. Variations in the contents of phenolics in grape seeds, skins, and pulp were high, but seeds contained higher levels of these phenolics than pulp and skin. Analyses of the relationship between two viticultural diseases and phenolic changes in resistant/tolerant cultivars in relation with the susceptible “Italia” cultivar revealed that an increase in the content of the phenolic compounds was found after powdery mildew disease. Hybrids/cultivars with high phenolic contents are recommended to develop new superior cultivars, which are resistant to grape fungal diseases, in breeding programs.

Effects of exogenous methyl jasmonate and light condition on grape berry coloration and endogenous abscisic acid content.

Suitable postharvest treatment methods were investigated to improve the color of grape berries. Culture solutions containing jasmonic acid (JA), methyl jasmonate (MeJA), and prohydrojasmon (PDJ) enhanced the skin coloration of grape berries (‘Pione’) harvested at the initial stage of coloration. MeJA vapor treatment under sealed conditions increased anthocyanin accumulation in grape berries (‘AkiQueen’ and ‘Pione’) harvested at the early stage of skin coloration. Furthermore, promoting skin coloration by MeJA vapor treatment was as effective in mature clusters as it was in detached berries. These effects were confirmed in light conditions but not in constant darkness. Our results showed that postharvest MeJA vapor treatment improved skin coloration in grapes. In addition, postharvest treatment with MeJA was found to have no effect on the endogenous abscisic acid content of grape berry skins. Therefore, we suggest that MeJA vapor treatment can be a useful and labor-saving method for the horticultural industry.

Ethylene Induced by Sound Stimulation Enhances Anthocyanin Accumulation in Grape Berry Skin through Direct Upregulation of UDP-Glucose: Flavonoid 3-O-Glucosyltransferase.

Global warming has resulted in the loss of anthocyanin accumulation in berry skin. Sound stimulation can be used as a potential method for enhancing fruit color development since many plants recognize sound vibration as an external stimulus and alter their physiological status in response to it. Sound stimulation (sine wave sound at 1000 Hz) enhanced anthocyanin accumulation in grape cultured cells and berry skins in field-grown grapevines at the early stage of ripening. The transcription of UFGT and ACO2, which encode the key enzymes in anthocyanin and ethylene biosynthesis, respectively, was upregulated in grape cultured cells exposed to sound stimulation. In contrast, the transcription of MybA1 and NCED1, which encode a transcription factor for UFGT and a key enzyme in abscisic acid biosynthesis, respectively, was not affected by the sound stimulation. A treatment with an ethylene biosynthesis inhibitor, aminoethoxyvinyl glycine hydrochloride, revered the enhancement of anthocyanin accumulation by sound stimulation. As the promoter assay using a GUS reporter gene demonstrated that UFGT promoter was directly activated by the ethylene-releasing compound ethephon, which enhanced anthocyanin accumulation in grape cultured cells, we conclude that sound stimulation enhanced anthocyanin accumulation through the direct upregulation of UFGT by ethylene biosynthesis. Our findings suggest that sound stimulation contributes to alleviating poor coloration in berry skin as a novel and innovative practical technique in viticulture.