miR156b-targeted VvSBP8/13 functions downstream of the abscisic acid signal to regulate anthocyanins biosynthesis in grapevine fruit under drought.

Anthocyanins are the primary color components of grapevine berries and wines. In cultivation practices, a moderate water deficit can promote anthocyanin accumulation in red grape skins. Our previous study showed that abscisic acid (ABA) plays a key role in this process. Herein, we identified a microRNA, vv-miR156b, that is generated in grapevine berries in response to drought stress, along with increasing anthocyanin content and biosynthetic structural gene transcripts. In contrast, vv-miR156b short tandem target mimic (STTM) function-loss callus exhibits the opposite phenotype. Results from in vivo and in vitro experiments revealed that the ABA-signaling-regulated transcription factor VvAREB2 binds directly to the ABA-responsive element (ABRE) of the MIR156b promoter and activates miR156b expression. Furthermore, two miR156b downstream targets, VvSBP8 and VvSBP13, exhibited reduced grape anthocyanin content in their overexpressors but there was a contrary result in their CRISPR-edited lines, the decrease in anthocyanin content was rescued in miR156b and SBP8/13 double overexpressors. We further demonstrated that both VvSBP8 and VvSBP13, encoding transcriptional repressors, displayed sufficient ability to interact with VvMYC1 and VvMYBA1, thereby interfering with MYB-bHLH-WD (MBW) repeat transcriptional complex formation, resulting in the repression of anthocyanin biosynthesis. Our findings demonstrate a direct functional relationship between ABA signaling and the miR156-SBP-MBW complex regulatory module in driving drought-induced anthocyanin accumulation in grape berries.

Evolution of volatile profile and aroma potential of 'Gold Finger' table grapes during berry ripening.

BACKGROUND: 'Gold Finger' is a grape cultivar with a finger-like shape and a milk flavor. The process by which its aroma profile evolves during ripening is unclear. Thus, changes in the free and bound volatile compounds present in 'Gold Finger' grapes during ripening were investigated using headspace sampling-solid-phase microextraction-gas chromatography-mass spectroscopy (HS-SPME-GC-MS). RESULTS: A total of 83 volatile aroma components were identified in the grapes, with aldehydes, esters, acids, and alcohols being the main components. The total aroma compound content exhibited significant differences between the bound and free forms. The total content of bound volatile compounds did not change significantly during fruit development, although the free aroma compound content was significantly higher than the bound content. The total content of free aldehydes, free alcohols, bound norisoprenoids, and ketones gradually increased for up to 70 days after flowering (DAF), while the total free ester, terpene, and acid content decreased. The characteristic aroma compounds of 'Gold Finger' grapes were identified as hexanal, (E)-2-hexenal, and ethyl hexanoate. CONCLUSIONS: These results give a foundation for the further development of 'Gold Finger' grapes and provide a theoretical basis for the selection and breeding of novel aromatic grape varieties. © 2021 Society of Chemical Industry.

Functional Characterization of VDACs in Grape and Its Putative Role in Response to Pathogen Stress.

Voltage-dependent anion channels (VDACs) are the most abundant proteins in the mitochondrial outer membranes of all eukaryotic cells. They participate in mitochondrial energy metabolism, mitochondria-mediated apoptosis, and cell growth and reproduction. Here, the chromosomal localizations, gene structure, conserved domains, and phylogenetic relationships were analyzed. The amino acid sequences of VDACs were found to be highly conserved. The tissue-specific transcript analysis from transcriptome data and qRT-PCR demonstrated that grapevine VDACs might play an important role in plant growth and development. It was also speculated that VDAC3 might be a regulator of modulated leaf and berry development as the expression patterns during these developmental stages are up-regulated. Further, we screened the role of all grape VDACs' response to pathogen stress and found that VDAC3 from downy mildew Plasmopara viticola-resistant Chinese wild grapevine species Vitis piasezkii "Liuba-8" had a higher expression than the downy mildew susceptible species Vitis vinifera cv. "Thompson Seedless" after inoculation with P. viticola. Overexpression of VpVDAC3 resulted in increased resistance to pathogens, which was found to prevent VpVDAC3 protein accumulation through protein post-transcriptional regulation. Taken together, these data indicate that VpVDAC3 plays a role in P. viticola defense and provides the evidence with which to understand the mechanism of grape response to pathogen stress.

Evolution of volatile profile and aroma potential of table grape Hutai-8 during berry ripening.

Hutai-8 (Vitis vinifera × Vitis labrusca) is a table grape widely cultivated in China. In order to determine the changes in volatile profile and aroma potential during berry ripening, a total of 84 free and 73 bound aroma compounds were identified and quantified using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Aldehydes and esters were found to be the main volatile compounds in Hutai-8. They accumulated up to 70 days after flowering (DAF) and then decreased. Bound esters and alcohols were prominent. The concentration of bound esters in Hutai-8 at DAF80 was 714.90 µg/L. ß-Damascenone, hexanal, (E)-2-hexenal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, and ethyl octanoate significantly contributed to the volatile profile of Hutai-8. The odor activity value (OAV) of hexanal was the highest at DAF80, reaching 351.51. ß-Damascenone mainly appeared midway through the maturation process, reaching a concentration of 12.79 µg/L. The majority of free components reached a maximum in DAF70, while the bound components continuously accumulated throughout the mature period. These results suggest that in addition to being a table grape, Hutai-8 has potential for brewing and other processing.

Plant-derived melatonin from food: a gift of nature.

In recent years, people have become increasingly interested in bioactive ingredients from plants, especially antioxidant molecules such as melatonin, which are beneficial to human health. The purpose of this article is to provide new information on plant-derived foods with a high content of melatonin. We comprehensively summarize the content of melatonin in plant-derived foods and discuss the factors that influence melatonin levels to provide new ideas on enhancement. Additionally, we describe the biosynthetic pathway of melatonin and identify its major functions. Medicinal herbs are often rich in melatonin while many vegetables and fruits exhibit somewhat lower levels with wide variations among species. The genetic traits of plants, the phenological stage of the cultivar, the photoperiod, the level of stress to which the plants are exposed at the time of harvest, exposure to agrochemicals and determination methods are the main factors affecting the melatonin content. To date, standardization of uniform sampling times and the use of suitable pretreatments as well as determination methods have not been achieved. The results of the studies reviewed highlight the potentially important role of plant melatonin in influencing the progression of human diseases. Based on the health promotional aspects of melatonin, consuming foods containing higher concentrations of tryptophan and melatonin is suggested.

Cluster bagging promotes melatonin biosynthesis in the berry skins of Vitis vinifera cv. Cabernet Sauvignon and Carignan during development and ripening.

Melatonin, a tryptophan derivative, is an important functional component in grape berries. We investigated the effect of cluster bagging on melatonin biosynthesis in the berries of two wine grape cultivars, Cabernet Sauvignon and Carignan, during fruit development and ripening. Cluster bagging delayed fruit coloring and ripening, and bag-treated berries of both grape cultivars synthesized more melatonin and most of the precursor compounds including L-tryptophan, N-acetylserotonin, tryptamine, and serotonin compared to those exposed to light (control) conditions. Interestingly, 5-methoxytryptamine was only detected in the berries of Carignan and not of Cabernet Sauvignon, both in the cluster bagging and control groups. In addition, melatonin and most of its precursors, decreased after veraison. VvSNAT1 and VvT5H expression levels were positively correlated with melatonin content. Our findings suggested that melatonin synthesis pathways differ among grape cultivars, and that VvSNAT1 and VvT5H may show key regulatory roles in the melatonin synthesis of grape berries.

Harvesting at the Right Time: Maturity and Its Effects on the Aromatic Characteristics of Cabernet Sauvignon Wine.

The aim of this paper was to investigate how maturity affects the aroma characteristics of Cabernet Sauvignon wine. A series of four Vitis vinifera cv. Cabernet Sauvignon wines were produced from grapes of different harvest dates. The berries of sequential harvest treatments showed an increase in total soluble solids and anthocyanin and a decrease in titratable acidity. Berry shriveling was observed as berry weight decreased. In the wines, anthocyanin, dry extract, alcoholic strength, and pH were enhanced with the sequential harvest, whereas polyphenol and tannin were decreased. The concentrations of volatile compounds in sequential harvests were found to be at higher levels. Isopentanol, phenylethyl alcohol, ethyl acetate, ethyl lactate, benzaldehyde, citronellol, and linalool significantly increased when harvest was delayed by one or two weeks. Through a principal component analysis, the volatile compounds and phenols characterizing each harvest date were clearly differentiated. These results suggest that sequential harvest may be an optional strategy for winemakers to produce high-quality wine.

Dynamic changes in anthocyanin biosynthesis regulation of Cabernet Sauvignon (Vitis vinifera L.) grown during the rainy season under rain-shelter cultivation.

The grapevine (Vitis vinifera L.) berry coloring mechanism in response to seasonal rain during grape ripening remains poorly understood. Therefore, anthocyanin biosynthesis regulation, dynamic changes in anthocyanin accumulation, biosynthetic enzyme activities, and related gene expression patterns were investigated in Cabernet Sauvignon grown under rain-shelter cultivation and open-field cultivation. Results showed that anthocyanin biosynthesis was strongly repressed during the rainy season. Environmental fluctuation from seasonal rain provoked metabolic responses in grapes, and there was a significantly greater accumulation of most of the anthocyanins, mainly the compositions of non-acylated and non-methylated, under rain-shelter cultivation; these findings indicate that rain-shelter cultivation may help improve tolerance to seasonal rain-induced stresses. Obvious resilience was observed in anthocyanins of open-field-cultivated grapes at harvest. Hierarchical cluster analysis indicated strong correlations between anthocyanin contents, CHI and DFR activities, and VvMYB5b transcriptional level. These findings provide novel insight into the crucial factors that directly modulate anthocyanin biosynthesis and consequently control grape coloration.

Influence of natural variation in berry size on the volatile profiles of Vitis vinifera L. cv. Merlot and Cabernet Gernischt grapes.

This study was conducted during the 2014 and 2015 vintages on Vitis vinifera L. cv. Merlot and Cabernet Gernischt to investigate whether natural variation in berry size could affect grape aromatic compounds. Grape berries were separated into three size categories based on their diameter: small, middle and large. The results showed that berry size exerted a significant influence on the volatile profiles of both winegrape varieties. Hierarchical clustering analysis demonstrated that the volatile profiles of middle berries were different from those of large and small berries. Middle berries had the greatest abundance of aroma compounds, followed by small and large berries. Especially, C6/C9 compounds, norisoprenoids, terpenoids showed markedly different concentrations among differently sized Merlot berries and C6/C9 compounds, terpenoids among differently sized Cabernet Gernischt berries. Middle berries of both grape varieties may possess the greatest intensity of fresh-green, fruity and floral aromas due to the high odour activity values (OAVs) of decanal, hexanal, (E)-2-hexenal, (E)-ß-damascenone and ß-ionone in middle sizes of Merlot berries and the high OAVs of (E)-2-hexenal and (E)-ß-damascenone in middle sizes of Cabernet Gernischt berries. This knowledge could be important for winemakers to conduct targeted berry sorting, thereby improving the aromatic quality of grapes.

Exogenous 24-Epibrassinolide alleviates oxidative damage from copper stress in grape (Vitis vinifera L.) cuttings.

Copper (Cu) stress is the most common abiotic stress experienced in vineyards owing to the copper-based fungicides application. Plant hormones, including 24-Epibrassinolide (EBR), may alleviate the adverse impacts of heavy metal stress on plants. We investigated the effects of EBR pretreatment on root morphological parameters, active oxygen metabolism, osmolytes contents, antioxidant enzyme activity, endogenous phytohormone contents, and ascorbate-glutathione (AsA-GSH) cycle activity of one-year-old grape (Vitis vinifera L.) cuttings under Cu stress. Pretreatment with EBR significantly enhanced root morphological parameters (total root length, root surface area, root diameter, root volume, and tip number), increased soluble protein and proline contents, and significantly decreased the contents of H2O2, O2⋅-, and malondialdehyde (MDA) in roots and leaves. EBR pretreatment increased the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase oxidase (POD), and the contents of the endogenous phytohormones abscisic acid, jasmonic acid, and salicylic acid in the leaves. In addition, EBR regulated the balance of the AsA-GSH cycle by increasing the activities of monodehydroascorbate reductase (MDHAR), glutathione peroxidase (GR), ascorbate peroxidase (APX), and dehydroascorbate reductase (DHAR), and the contents of the antioxidant ascorbate (AsA) and dehydroascorbic acid (DHA), but the contents of glutathione (GSH) and oxidized glutathione (GSSG) decreased. Among the treatments tested, pretreatment with 0.10 mg/L EBR showed the optimal performance for alleviation of Cu toxicity. The results show that exogenous brassinosteroids reduce oxidative damage and improve the tolerance of Cu stress of grapevine cuttings.

Foliar applications of iron promote flavonoids accumulation in grape berry of Vitis vinifera cv. Merlot grown in the iron deficiency soil.

Flavonoids are important compounds for grape and wine quality. Foliar fertilization with iron compounds has been reported to have a substantial impact on grape composition in the grapevines growing in calcareous soil. However, much less is known about its real impact on flavonoid composition. In the present study, Ferric ethylenediamine di (O-hydroxyphenylacetic) acid (Fe-EDDHA) was foliar applied to Merlot (Vitis vinifera L.) grapevines growing in calcareous soil over two consecutive vintages in order to study its effect on grape flavonoid composition. Fe-EDDHA foliar supply tended to increase grape sugar, anthocyanin and flavonol content, decrease acid content and enhance the juice pH when compared to the control. Principal component analysis showed that the vintage also had influence on grape quality. The results suggested that Fe-EDDHA foliar application had an enhancement effect on grape secondary metabolism, and the effect increased the nutritional value of the consequent grapes and wines.

Reduction of Dihydrokaempferol by Vitis vinfera Dihydroflavonol 4-Reductase to Produce Orange Pelargonidin-Type Anthocyanins.

Vitis vinifera has been thought to be unable to produce pelargonidin-type anthocyanins because its dihydroflavonol 4-reductase (DFR) does not efficiently reduce dihydrokaempferol. However, in this study, pelargonidin 3- O-glucoside was detected in the skins of V. vinifera 'Pinot Noir', 'Cabernet Sauvignon', and 'Yan73', as well as in the flesh of 'Yan73' by HPLC-ESI-MS/MS. Additionally, pelargonidin 3- O-(6-acetyl)-glucoside was detected in 'Yan73' skin and flesh for the first time. To further confirm the presence of pelargonidin-type anthocyanins in these grape cultivars, their DFRs were cloned, expressed in Escherichia coli, and purified. An enzyme-activity analysis revealed that V. vinifera DFR can reduce dihydrokaempferol to produce leucopelargonidin, although it prefers dihydroquercetin and dihydromyricetin as substrates. Thus, the existence of a pelargonidin-based anthocyanin-biosynthetic pathway was confirmed in V. vinifera via mass-spectrometric and enzymatic methods and redirected anthocyanin biosynthesis in V. vinifera L. cultivars.

Exogenous 24-Epibrassinolide Interacts with Light to Regulate Anthocyanin and Proanthocyanidin Biosynthesis in Cabernet Sauvignon (Vitis vinifera L.).

Anthocyanins and proanthocyanidins (PAs) are crucial factors that affect the quality of grapes and the making of wine, which were stimulated by various stimuli and environment factors (sugar, hormones, light, and temperature). The aim of the study was to investigate the influence of exogenous 24-Epibrassinolide (EBR) and light on the mechanism of anthocyanins and PAs accumulation in grape berries. Grape clusters were sprayed with EBR (0.4 mg/L) under light and darkness conditions (EBR + L, EBR + D), or sprayed with deionized water under light and darkness conditions as controls (L, D), at the onset of veraison. A large amount of anthocyanins accumulated in the grape skins and was measured under EBR + L and L treatments, whereas EBR + D and D treatments severely suppressed anthocyanin accumulation. This indicated that EBR treatment could produce overlay effects under light, in comparison to that in dark. Real-time quantitative PCR analysis indicated that EBR application up-regulated the expression of genes (VvCHI1, VvCHS2, VvCHS3, VvDFR, VvLDOX, VvMYBA1) under light conditions. Under darkness conditions, only early biosynthetic genes of anthocyanin biosynthesis responded to EBR. Furthermore, we also analyzed the expression levels of the BR-regulated transcription factor VvBZR1 (Brassinazole-resistant 1) and light-regulated transcription factor VvHY5 (Elongated hypocotyl 5). Our results suggested that EBR and light had synergistic effects on the expression of genes in the anthocyanin biosynthesis pathway.

Methoxypyrazines biosynthesis and metabolism in grape: A review.

This review summarizes research on the discovery, biosynthesis, accumulation, transport, and metabolism of 3-alkyl-2-methoxypyrazines (MPs) in grape. The MPs are a family of potent volatile compounds distributed throughout biological kingdoms. These compounds impart herbaceous/green/vegetal sensory attributes to certain varieties of wine. Generally, high levels of MPs in wine are derived mainly from the corresponding grapes. Although two pathways for MPs biosynthesis have been proposed, only the final step and the enzymes that catalyze it has been confirmed in grape, and the metabolic intermediates and key enzymes involved in other steps are still unknown. The limited understanding of MPs metabolism has restricted research on these compounds, and some empirical results cannot be explained by the current knowledge of MPs metabolism. This review provides insights into research on MPs biosynthesis and metabolism, and proposes directions for further research on this important class of flavour/odour compounds.

Effect of regulated deficit irrigation on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines of Ningxia, China.

The effect of regulated deficit irrigation (RDI) on fatty acids and their derived volatiles in 'Cabernet Sauvignon' grapes and wines was investigated during two growing seasons in the east foot of Mt. Helan, the semi-arid area. The vines received water with 60% (RDI-1), 70% (RDI-2), 80% (RDI-3), 100% (CK, traditional drip irrigation) of their estimated evapotranspiration (ETc) respectively. RDI treatments resulted in lower yield, berry weight and titratable acidity with higher total soluble solids. RDI-1 increased the content of unsaturated fatty acids in berries and decreased the level of alcohols and esters volatiles in wines. RDI-2 and RDI-3 enhanced 1-hexanol and esters in wines in comparison with CK. The concentrations of C6 aroma compounds were closely correlated with unsaturated fatty acids (p < .05), especially linolenic acid and linoleic acid. The present results provided direct evidence and detailed data to explain the effect of RDI on grapes and wines composition regarding fatty acids and their derived volatiles.

Fruit sphere microenvironments and berry phenolic content of Cabernet Sauvignon (Vitis vinifera L.) cultivated under rain-shelter systems with coloured plastic film

Abstract Rain-shelter cultivation has been proven an important cultivation method for grape-plantings in continental monsoon climate zones, of which white plastic films are the most common shelter material. However, while this method and material reduces the occurrence of the disease, it can also decrease the grape berry quality. Five colours (including red, yellow, blue, purple, and white) of plastic films were covered above Cabernet Sauvignon (Vitis vinifera L.) grapevine rows before veraison. Rain-shelter cultivation reduced air temperature, wind speed, and total solar radiation and enhanced relative humidity in the fruit sphere of grapevines. For each particular colour plastic film, the irradiance of its corresponding spectrum band in the canopy of vines was higher than with other colour plastic films. Meanwhile, the blue plastic film treatment significantly promoted the accumulation of total phenolics, anthocyanins, flavonoids, tannins, and phenolic acids more than the other colours of plastic films. Blue plastic films are more beneficial for berry quality promotion of wine grapes, especially Cabernet Sauvignon, under rain-shelter cultivation in continental monsoon climate zones.

Melatonin in grapes and grape-related foodstuffs: A review.

A decade has passed since melatonin was first reported in grapes in 2006. During this time, melatonin has not only been found in the berries of most wine grape (Vitis vinifera L.) cultivars, but also in most grape-related foodstuffs, e.g. wine, grape juice and grape vinegar. In this review, we discuss the melatonin content in grapes and grape-related foodstuffs (especially wine) from previous studies, the physiological function of melatonin in grapes, and the factors contributing to the production of melatonin in grapes and wines. In addition, we identify future research needed to clarify the mechanisms of grape melatonin biosynthesis and regulation, and establish more accurate analysis methods for melatonin in grapes and wines.

Iron Supply Affects Anthocyanin Content and Related Gene Expression in Berries of Vitis vinifera cv. Cabernet Sauvignon.

Anthocyanins are important compounds for red grape and red wine quality, and can be influenced by supply of nutrients such as nitrogen, phosphorus, potassium, zinc, and iron. The present work aims to gain a better understanding of the effect of iron supply on anthocyanins concentration in grape berries. To this end, own-rooted four-year-old Cabernet Sauvignon grapevines (Vitis vinifera) were fertigated every three days with 0, 23, 46, 92, and 184 µM iron (Fe) from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA) in a complete nutrient solution. Fe deficiency or excess generally led to higher concentrations of titratable acidity and skin/berry ratio, and to lower reducing sugar content, sugar/acid ratio, pH, berry weight, and concentration of anthocyanins. Most of the individual anthocyanins detected in this study, except cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and cyanidin-3-O-(6-O-coumaryl)-glucoside, in moderate Fe treatment (46 µM) grapes were significantly higher than those of other treatments. Genes encoding chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), leucoanthocyanidin dioxygenase (LDOX), and anthocyanin O-methyltransferase (AOMT) exhibited higher transcript levels in berries from plants cultivated with 46 µM Fe compared to the ones cultivated with other Fe concentrations. We suggest that grape sugar content, anthocyanins content, and transcriptions of genes involved in anthocyanin biosynthesis were correlated with Fe supply concentrations.

Effect of Exogenous Abscisic Acid and Methyl Jasmonate on Anthocyanin Composition, Fatty Acids, and Volatile Compounds of Cabernet Sauvignon (Vitis vinifera L.) Grape Berries.

The anthocyanin composition, fatty acids, and volatile aromas are important for Cabernet Sauvignon grape quality. This study evaluated the effect of exogenous abscisic acid (ABA) and methyl jasmonate (MeJA) on the anthocyanin composition, fatty acids, lipoxygenase activity, and the volatile compounds of Cabernet Sauvignon grape berries. Exogenous ABA and MeJA improved the content of total anthocyanins (TAC) and individual anthocyanins. Lipoxygenase (LOX) activity also increased after treatment. Furthermore, 16 fatty acids were detected. The linoleic acid concentration gradually increased with ABA concentration. The fatty acid content decreased with increasing MeJA concentration and then increased again, with the exception of linoleic acid. After exogenous ABA and MeJA treatment, the C6 aroma content increased significantly. Interestingly, the exogenous ABA and MeJA treatments improved mainly the content of 1-hexanol, hexanal, and 2-heptanol. These results provide insight into the effect of plant hormones on wine grapes, which is useful for grape quality improvement.

Melatonin treatment of pre-veraison grape berries to increase size and synchronicity of berries and modify wine aroma components.

A comprehensive investigation was carried out to determine the effect of exogenous melatonin treatment of pre-veraison grapes on grape berries and its wines. Two melatonin treatments of pre-veraison grape berries increased the weight of the berries by approximately 6.6%. Meanwhile, this melatonin treatment could be beneficial in the reduction of underripe and overripe fruits and in enhancing the synchronicity of the berries. In addition, there were significant differences in the volatile compound composition between the wine produced from the melatonin-treated berries and the wines made from untreated berries. The wine from melatonin-treated pre-veraison grape berries had stronger fruity, spicy, and sweet sensory properties, compared to the wines made from untreated berries. Prolonging the treatment through repeated applications can enhance these effects and under different seasonal conditions, more pronounced effects on the grape quality and wine properties can be observed.