Modulation of volatile compound metabolome and transcriptome in grape berries exposed to sunlight under dry-hot climate

Integrated Transcriptomic and Metabolomic Analysis Revealed Abscisic Acid-Induced Regulation of Monoterpene Biosynthesis in Grape Berries

Monoterpenes are a class of volatile organic compounds that play crucial roles in imparting floral and fruity aromas to Muscat-type grapes. However, our understanding of the regulatory mechanisms underpinning monoterpene biosynthesis in grapes, particularly following abscisic acid (ABA) treatment, remains elusive. This study aimed to explore the impact of exogenous ABA on monoterpene biosynthesis in Ruiduhongyu grape berries by employing Headspace Solid-Phase Micro-Extraction Gas Chromatography-Mass Spectrometry (HS-SPME/GC-MS) analysis and transcriptome sequencing. The results suggested significant differences in total soluble solids (TSS), pH, and total acid content. ABA treatment resulted in a remarkable increase in endogenous ABA levels, with concentrations declining from veraison to ripening stages. ABA treatment notably enhanced monoterpene concentrations, particularly at the E_L37 and E_L38 stages, elevating the overall floral aroma of grape berries. According to the variable gene expression patterns across four developmental stages in response to ABA treatment, the E_L37 stage had the largest number of differential expressed genes (DEGs), which was correlated with a considerable change in free monoterpenes. Furthermore, functional annotation indicated that the DEGs were significantly enriched in primary and secondary metabolic pathways, underlining the relationship between ABA, sugar accumulation, and monoterpene biosynthesis. ABA treatment upregulated key genes involved in the methylerythritol phosphate (MEP) pathway, enhancing carbon allocation and subsequently impacting terpene synthesis. This study also identified transcription factors, including MYB and AP2/ERF families, potentially modulating monoterpene and aroma-related genes. Weighted gene co-expression network analysis (WGCNA) linked ABA-induced gene expression to monoterpene accumulation, highlighting specific modules enriched with genes associated with monoterpene biosynthesis; one of these modules (darkgreen) contained genes highly correlated with most monoterpenes, emphasizing the role of ABA in enhancing grape quality during berry maturation. Together, these findings provide valuable insights into the multifaceted effects of exogenous ABA on monoterpene compounds and grape berry flavor development, offering potential applications in viticulture and enology.

Effect of Cluster-Zone Leaf Removal at Different Stages on Cabernet Sauvignon and Marselan (Vitis vinifera L.) Grape Phenolic and Volatile Profiles

This study investigated the effect of leaf removal at three stages of grape development on the phenolic and volatile profiles of Cabernet Sauvignon and Marselan grapevines for two consecutive years in the Jieshi Mountain region, an area of eastern China with high summer rainfall. The results indicated that cluster-zone leaf removal generally reduced the titratable acidity of both varieties, but did not affect the total soluble solids of grape berries. Leaf-removal treatments increased the anthocyanin and flavonol content of berries in both varieties. However, in Cabernet Sauvignon, leaf removal negatively affected the norisoprenoid compounds, with a more pronounced impact observed when the leaf removal was conducted at an early stage. This negative effect may be related to a decrease in the levels of violaxanthin and neoxanthin, potential precursors of vitisprine and β-damascenone. In contrast, the removal of leaves had no effect on the norisoprenoid aroma of Marselan grapes.

Effects of full shading of clusters from véraison to ripeness on fruit quality and volatile compounds in Cabernet Sauvignon grapes

Sunlight exposure of grape clusters is frequently reported to influence grape aromas greatly. Among them, the effects of full shading (FS) of clusters on fruit quality and volatile compounds in grape berries has scarcely been investigated. In the present study, the effects of FS from véraison to ripeness on fruit quality and volatile compounds in Cabernet Sauvignon grapes were studied. The results showed that FS treatment reduced fruit size and berry weight, delayed fruit maturity, and decreased the contents of anthocyanins, phenols, and tannins in grape berries. In addition, volatile compounds in grape berries were analyzed, and 55 and 53 volatile compounds were detected in the control (CK) and FS groups, respectively. The results indicated that the concentrations of straight-chain fatty aldehydes, straight-chain fatty alcohols, straight-chain fatty acids, and branched-chain fatty acids, norisoprenoids, and total concentration of volatile compounds were all higher in FS group than in CK group. Specifically, FS treatment had significant promoting effects on the concentrations of β-damascenone, terpineol, 2-ethyl-1-hexanol, and 2-hexenal, and remarkably decreased the concentrations of geranial, benzeneacetaldehyde, neral, and ethyl acetate. Partial least squares-discriminant analysis (PLS-DA) revealed a clear separation between the control (CK) and FS groups, and showed that 2-hexenal and hexanal were the main characteristic aroma compounds in the FS group. Moreover, an increase in the intensity of fruity, herbaceous, floral, and mushroom aromas was recorded in FS grapes. This study provides new insights into the effects of the exclusion of sunlight exposure on volatile compound accumulation in grape berries.

Changes in Physiological Indices, Amino Acids, and Volatile Compounds in Vitis vinifera L. cv. Pinot Noir under UV-B Radiation and Water Deficit Conditions

UV-B radiation and water deficit can challenge Pinot noir growth and fruit quality. The aim of this work is to determine the effects of UV-B and water deficit on the physiological indices, amino acids, and volatile compounds of Pinot noir vine and fruit. The results showed that both individual and combined treatments caused a decrease in the leaf SPAD, with the largest amplitude being observed in the combined treatment. Water deficit also decreased the leaf water potential and increased the juice δ13C‱ at harvest, which was the opposite of the latter under UV-B radiation. Interestingly, most of the physiological indices under combined stresses did not show significant changes compared with that under no UV-B and the well-watered control treatment. Moreover, the concentrations of amino acids and volatile compounds in the berries were determined at harvest. The amino acid contents were significantly increased by the combined treatment, particularly proline (Pro), aspartate (Arg), alanine (Ala), and threonine (Thr). There were slight increases in volatile compounds. This research substantially contributed to improve our scientific understanding of UV-B and water deficit responses in an important commercial species. In addition, it highlighted some future research to produce high-quality wines with the anticipated specific characteristics.

Vineyard soil heterogeneity and harvest date affect volatolomics and sensory attributes of Cabernet Sauvignon wines on a meso-terroir scale

To produce premium wines in a specific region is the goal of local oenologists. This study aimed to investigate the influence of soil properties and harvest date on the volatolomics of wine to provide a better insight into single-vineyard wines. Six Cabernet Sauvignon vineyards were selected in a semi-arid region to produce their wines at three harvest ripeness levels ranging from 23°Brix-28°Brix in three seasons (2019-2021). Results showed that among all six vineyards, the vineyard with the highest soil pH produced wines with lower C6 alcohols and herbaceous aroma. Moderate nutrition in soils was beneficial for the accumulation of β-damascenone and enhanced fruity and floral aroma in wines while over-fertile soil produced wines with the lowest sensory score. As the harvest ripeness elevated, the wine's fruity and floral aroma intensity decreased. Through advanced network analysis, the key volatiles such as β-damascenone, ethy1 lactate, and isoamyl octanoate, and their interaction in affecting wine sensory scores were evaluated. Our study provided a concept for producing premium single-vineyard wines.

The flavour of grape colour: anthocyanin content tunes aroma precursor composition by altering the berry microenvironment

Anthocyaninless (white) instead of black/red (coloured) fruits develop in grapevine cultivars without functional VviMYBA1 and VviMYBA2 genes, and this conditions the colour of wines that can be produced. To evaluate whether this genetic variation has additional consequences on fruit ripening and composition, we performed comparisons of microenvironment, transcriptomics, and metabolomics of developing grapes between near-isogenic white- and black-berried somatic variants of Garnacha and Tempranillo cultivars. Berry temperature was as much as 3.5 ºC lower in white- compared to black-berried Tempranillo. An RNA-seq study combined with targeted and untargeted metabolomics revealed that ripening fruits of white-berried variants were characterized by the up-regulation of photosynthesis-related and other light-responsive genes and by their higher accumulation of specific terpene aroma precursors, fatty acid-derived aldehyde volatiles, and phenylpropanoid precursor amino acids. MYBA1-MYBA2 function proved essential for flavonol trihydroxylation in black-berried somatic variants, which were also characterized by enhanced expression of pathogen defence genes in the berry skin and increased accumulation of C6-derived alcohol and ester volatiles and γ-aminobutyric acid. Collectively, our results indicate that anthocyanin depletion has side-effects on grape composition by altering the internal microenvironment of the berry and the partitioning of the phenylpropanoid pathway. Our findings show how fruit colour can condition other fruit features, such as flavour potential and stress homeostasis.

Transcription factor VvWRKY70 inhibits both norisoprenoid and flavonol biosynthesis in grape

Norisoprenoids and flavonols are important secondary metabolites in grape berries (Vitis vinifera L.). The former is a class of ubiquitous flavor and fragrance compounds produced by the cleavage of carotenoids, and the latter, which is derived from the flavonoid metabolic pathway, has been proposed as a general quality marker for red grapes. However, the transcriptional regulatory mechanisms underlying norisoprenoid and flavonol production are still not fully understood. In this study, we characterized a transcription factor, VvWRKY70, as a repressor of both norisoprenoid and flavonol biosynthesis in grape berries, and its expression was downregulated by light and high-temperature treatment. Overexpressing VvWRKY70 in grape calli reduced norisoprenoid and flavonol production, particularly under light exposure or at high temperature, by repressing the expression of several related genes in the isoprenoid and flavonoid metabolic pathways. VvWRKY70 downregulated β-CAROTENE HYDROXYLASE 2 (VvBCH2) and CHALCONE SYNTHASE 3 (VvCHS3) expression based on yeast 1-hybrid analysis combined with electrophoretic mobility shift assay and chromatin immunoprecipitation-quantitative PCR. We discuss the role of VvWRKY70 in the coordinated regulatory network of isoprenoid and flavonoid metabolism. These findings provide a theoretical basis to improve flavor, color, and other comprehensive qualities of fruit crops and their processing products.

Aroma precursors of Grignolino grapes (Vitis vinifera L.) and their modulation by vintage in a climate change scenario

Current climatic conditions may cause significant changes in grapevine phenology and maturity dynamics linked often with changes to ecoclimatic indicators. The influence exerted by different meteorological conditions during four consecutive years on the aromatic potential of Grignolino grapes was investigated for the first time. The samples were collected from three vineyards characterized by different microclimatic conditions mainly related to the vineyard exposure and by a different age of the plants. Important differences as far as temperature and rainfall patterns are concerned during ripening were observed among the 4 years. Grape responses to abiotic stress, with particular emphasis on aromatic precursors, were evaluated using gas chromatography coupled to mass spectrometry. The results highlighted significant differences among the vintages for each vineyard in terms of the berry weight and the aromatic precursor concentration. For the grapes of the younger-vine vineyard, the content of aroma compounds showed a different variability among the vintages if compared to the old-vine vineyards. Optimal conditions in terms of temperature and rainfall during the green phase followed by a warm and dry post-veraison period until harvest favored all classes of compounds especially terpenoids mainly in the grapes of the old vines. High-temperature (>30°C) and low-rainfall pattern before veraison led to high benzenoid contents and increased differences among vineyards such as berry weight, whereas cooler conditions favored the terpenoid levels in grapes from southeast-oriented vineyards. In a hilly environment, lack of rainfall and high temperature that lately characterize the second part of berry development seem to favor the grape quality of Grignolino, a cultivar of medium-late ripening, by limiting the differences on bunch ripening, allowing a greater accumulation of secondary metabolites but maintaining at the same time an optimum balance sugar/acidity.

The Combination of Both Heat and Water Stresses May Worsen Botryosphaeria Dieback Symptoms in Grapevine

(1) Background: Grapevine trunk diseases (GTDs) have become a global threat to vineyards worldwide. These diseases share three main common features. First, they are caused by multiple pathogenic micro-organisms. Second, these pathogens often maintain a long latent phase, which makes any research in pathology and symptomatology challenging. Third, a consensus is raising to pinpoint combined abiotic stresses as a key factor contributing to disease symptom expression. (2) Methods: We analyzed the impact of combined abiotic stresses in grapevine cuttings artificially infected by two fungi involved in Botryosphaeria dieback (one of the major GTDs), Neofusicoccum parvum and Diplodia seriata. Fungal-infected and control plants were subjected to single or combined abiotic stresses (heat stress, drought stress or both). Disease intensity was monitored thanks to the measurement of necrosis area size. (3) Results and conclusions: Overall, our results suggest that combined stresses might have a stronger impact on disease intensity upon infection by the less virulent pathogen Diplodia seriata. This conclusion is discussed through the impact on plant physiology using metabolomic and transcriptomic analyses of leaves sampled for the different conditions.

Overhead photoselective shade films mitigate effects of climate change by arresting flavonoid and aroma composition degradation in wine

INTRODUCTION

Overhead photoselective shade films installed in vineyards improve berry composition in hot grape-growing regions. The aim of the study was to evaluate the flavonoid and aroma profiles and composition of wines from Cabernet Sauvignon grapes (Vitis vinifera L.) treated with partial solar radiation exclusion.

METHODS

Experimental design consisted in a randomized experiment with four shade films (D1, D3, D4, D5) with differing solar radiation spectra transmittance and compared to an uncovered control (C0) performed over two seasons (2021 and 2022) in Oakville (CA, USA). Berries were collected by hand at harvest and individual vinifications for each treatment and season were conducted in triplicates. Then, wine chemical composition, flavonoid and aromatic profiles were analyzed.

RESULTS

The wines from D4 treatment had greater color intensity and total phenolic index due to co-pigmentation with anthocyanins. Shade film wines D5 and D1 from the 2020 vintage demonstrated increased total anthocyanins in the hotter of the two experimental years. In 2021, reduced cluster temperatures optimized total anthocyanins in D4 wines. Reduced cluster temperatures modulated anthocyanin acylation, methylation and hydroxylation in shade film wines. Volatile aroma composition was analyzed using gas chromatography mass spectroscopy (GCMS) and D4 wines exhibited a more fruity and pleasant aroma profile than C0 wines.

DISCUSSION

Results provided evidence that partial solar radiation exclusion in the vineyard using overhead shade films directly improved flavonoid and aroma profiles of resultant wines under hot vintage conditions, providing a tool for combatting air temperatures and warmer growing conditions associated with climate change.

Transcriptomic and metabolomic integration as a resource in grapevine to study fruit metabolite quality traits

Transcriptomics and metabolomics are methodologies being increasingly chosen to perform molecular studies in grapevine (Vitis vinifera L.), focusing either on plant and fruit development or on interaction with abiotic or biotic factors. Currently, the integration of these approaches has become of utmost relevance when studying key plant physiological and metabolic processes. The results from these analyses can undoubtedly be incorporated in breeding programs whereby genes associated with better fruit quality (e.g., those enhancing the accumulation of health-promoting compounds) or with stress resistance (e.g., those regulating beneficial responses to environmental transition) can be used as selection markers in crop improvement programs. Despite the vast amount of data being generated, integrative transcriptome/metabolome meta-analyses (i.e., the joint analysis of several studies) have not yet been fully accomplished in this species, mainly due to particular specificities of metabolomic studies, such as differences in data acquisition (i.e., different compounds being investigated), unappropriated and unstandardized metadata, or simply no deposition of data in public repositories. These meta-analyses require a high computational capacity for data mining a priori, but they also need appropriate tools to explore and visualize the integrated results. This perspective article explores the universe of omics studies conducted in V. vinifera, focusing on fruit-transcriptome and metabolome analyses as leading approaches to understand berry physiology, secondary metabolism, and quality. Moreover, we show how omics data can be integrated in a simple format and offered to the research community as a web resource, giving the chance to inspect potential gene-to-gene and gene-to-metabolite relationships that can later be tested in hypothesis-driven research. In the frame of the activities promoted by the COST Action CA17111 INTEGRAPE, we present the first grapevine transcriptomic and metabolomic integrated database (TransMetaDb) developed within the Vitis Visualization (VitViz) platform (https://tomsbiolab.com/vitviz). This tool also enables the user to conduct and explore meta-analyses utilizing different experiments, therefore hopefully motivating the community to generate Findable, Accessible, Interoperable and Reusable (F.A.I.R.) data to be included in the future.

Reducing the source/sink ratio of grapevine to face global warming in a semi-arid climate: Effects on volatile composition of Cabernet Sauvignon grapes and wines

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Distal leaf removal increased the solar radiation of the cluster zone in the first few days after applying LR treatments.

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Distal leaf removal was beneficial for accumulating C6 alcohols, terpenes, and the free form of (Z)-β-damascenone in grapes.

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Distal leaf removal significantly increased the fruity and floral intensity of wines because of the increased esters and β-damascenone.

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Whether leaf removal in the same vines over consecutive years or not (1-LRs vs 2-LRs) had limited effects on wines aroma profiles.

The heterogeneity of the vineyard environment caused high variability in grape metabolites and flavor profiles, and the phenomenon was more prominent in recent years of climate change. Herein, distal leaf removal was applied in semi-arid Xinjiang to adjust the source to sink ratio of grapevines for three consecutive years (2018–2020). The grape-derived volatiles showed high correlations with specific climate factors such as temperature changes in the growth period. Results showed that distal leaf removal increased the solar radiation reaching the clusters in the first few days after applying LR treatments while not affecting the temperature. The improvement in fruity and floral aroma intensity by distal leaf removal was founded not only in grape metabolites but also in wines. Moderate cluster exposure brought by distal leaf removal was beneficial for the accumulation of isoprenoids, which therefore increased the fruity and floral intensity of wines. The carry-over effect did not show in consecutively defoliated vines among vintages regarding the wine aroma profile.

Monoterpenoids Evolution and MEP Pathway Gene Expression Profiles in Seven Table Grape Varieties

This research investigated the evolution of both monoterpenoids and expression profiles of related biosynthesis genes in the MEP pathway in seven different table grape varieties from veraison to maturity stage in two seasons, and the correlation was further evaluated between monoterpenoid accumulation and expression of these genes studied in these varieties. Results showed that linalool, trans-furan linalool oxide, geraniol, and cis-furan linalool oxide were the main compounds in the five Muscat varieties two seasons. ‘Zaomeiguixiang’ had the highest contents of geraniol and β-Citronellol. ‘Xiangfei’ had the most abundant of linalool and cis-furan linalool oxide, whereas the neutral varieties of ‘Moldova’ and ‘Christmas Rose’ had the least amount. Monoterpenoid volatiles have been grouped in three evolutionary patterns in the berry development of these varieties. ‘Zaomeiguixiang’ and ‘Xiangfei’ had distinct different pattern of terpenoids evolution profiles. Pearson’s correlation analysis showed that in the MEP pathway, the first biosynthesis gene VvDXS3 was significantly correlated to the accumulation of monoterpenoids, and appeared to be an important candidate gene for synthesis of the monoterpenoids.

The Effect of Topo-Climate Variation on the Secondary Metabolism of Berries in White Grapevine Varieties (Vitis vinifera)

Exploiting consistent differences in radiation and average air temperature between two experimental vineyards (Ramat Negev, RN and Mitzpe Ramon, MR), we examined the impact of climate variations on total carotenoids, redox status, and phenylpropanoid metabolism in the berries of 10 white wine grapevine (Vitis vinifera) cultivars across three consecutive seasons (2017-2019). The differences in carotenoid and phenylpropanoid contents between sites were seasonal and varietal dependent. However, the warmer RN site was generally associated with higher H₂O₂ levels and carotenoid degradation, and lower flavonol contents than the cooler MR site. Enhanced carotenoid degradation was positively correlated with radiation and daily degree days, leading to a greater drop in content from véraison to harvest in Colombard, Sauvignon Blanc, and Semillon berries. Analyses of berry H₂O₂ and phenylpropanoids suggested differences between cultivars in the links between H₂O₂ and flavonol contents. Generally, however, grapes with higher H₂O₂ content seem to have lower flavonol contents. Correlative network analyses revealed that phenylpropanoids at the warmer RN site are tightly linked to the radiation and temperature regimes during fruit ripening, indicating potentially harmful effect of warmer climates on berry quality. Specifically, flavan-3-ols were negatively correlated with radiation at RN. Principal component analysis showed that Muscat Blanc, Riesling, Semillon, and Sauvignon Blanc were the most site sensitive cultivars. Our results suggest that grapevine biodiversity is likely the key to withstand global warming hazards.

Effects of Defoliation Treatments of Babica Grape Variety(Vitis vinifera L.) on Volatile Compounds Content in Wine

The aim of this study was to determine the effects of defoliation performed in the Babica red grape variety on the volatile compounds in produced wine. Three treatments were performed during 2017 and 2018: the removal of six leaves before flowering (FL) and at the end of veraison (VER), as well as control (C). Volatile compounds were analyzed using a gas chromatograph coupled to a mass spectrophotometric detector. Results were statistically evaluated by analysis of variance (ANOVA at the p = 0.05 level) and principal component analysis (PCA). Defoliation treatments were affected by the concentration of several compounds, but only in one year. The VER2017 treatment significantly increased the concentration of three aliphatic esters up to 8 C atoms and octanoic acid ethyl ester. The FL2017 treatment increased the concentration of three aliphatic alcohols. The FL2018 treatment has significantly enhanced the concentration ethyl cinnamate but decreased the concentrations of eugenol and dihydro-2-methyl-3(2H)-thiophenone. Both defoliation treatments reduced the concentration of γ-decanolactone in 2017. Aldehydes, monoterpenoles, and monoterpenes remained unaffected by the defoliation treatments. Vintage was found to be the largest source of variability for most volatile compounds under investigation, which was confirmed by PCA. The effect of defoliation in the mild-Mediterranean climate was found to mostly depend on seasonal weather conditions.

Biogenic volatile organic compounds in the grapevine response to pathogens, beneficial microorganisms, resistance inducers, and abiotic factors

The synthesis of volatile organic compounds (VOCs) in plants is triggered in response to external stimuli, and these compounds can migrate to distal tissues and neighbouring receivers. Although grapevine VOCs responsible for wine aroma and plant-insect communications are well characterized, functional properties of VOCs produced in response to phytopathogens, beneficial microorganisms, resistance inducers, and abiotic factors have been less studied. In this review, we focused on the emission patterns and potential biological functions of VOCs produced by grapevines in response to stimuli. Specific grapevine VOCs are emitted in response to the exogenous stimulus, suggesting their precise involvement in plant defence response. VOCs with inhibitory activities against pathogens and responsible for plant resistance induction are reported, and some of them can also be used as biomarkers of grapevine resistance. Likewise, VOCs produced in response to beneficial microorganisms and environmental factors are possible mediators of grapevine-microbe communications and abiotic stress tolerance. Although further functional studies may improve our knowledge, the existing literature suggests that VOCs have an underestimated potential application as pathogen inhibitors, resistance inducers against biotic or abiotic stresses, signalling molecules, membrane stabilizers, and modulators of reactive oxygen species. VOC patterns could also be used to screen for resistant traits or to monitor the plant physiological status.

Secondary Metabolites Coordinately Protect Grapes from Excessive Light and Sunburn Damage during Development

Sunburn is a physiological disorder that reduces grape quality and vineyard yield. It is the result of excessive sunlight and high temperatures. As climate change continues to increase air temperatures, reports of sunburn damage in vineyards worldwide are becoming more frequent. Grapes produce secondary metabolites (carotenoids, polyphenols and aroma compounds) to counter photooxidative stress and acclimate to higher radiation environments. This study evaluated changes in these compounds in during ripening when grapes were exposed post-flowering (ED) and at véraison (LD), and compared them to a nondefoliated control (ND). ND contained more α-terpineol and violaxanthin, and the defoliated treatments contained more zeaxanthin, β-carotene, C₆ compounds and flavonoids. ED berries adapted better to higher-light environments, displayed larger changes in secondary metabolite concentrations and lower levels of sunburn damage than LD berries did. The composition of berries with increasing sunburn damage was evaluated for the first time. Berries with no damage had the lowest concentrations of flavonoids and oxidized glutathione, and the highest concentrations of chlorophyll and α-terpineol. As damage increased, destruction of photosynthetic pigments, increase in polyphenols and loss of aroma compounds were evidenced. A significant effect of temperature and developmental stage on grape composition was also observed. This study provides a holistic overview of changes in secondary metabolites experienced by grape berries when exposed to excessive light, how these vary along development and how they affect sunburn incidence.

Influence of cluster positions in the canopy and row orientation on the flavonoid and volatile compound profiles in Vitis vinifera L. Cabernet franc and Chardonnay berries

Sunlight conditions around grape clusters vary with their positions, and can have a significant effect on grape berry compounds. This study investigated the influence of cluster positions in the canopy (interior and two exterior canopy sides) and vineyard row orientation (north-south and east-west) on flavonoid and volatile compound profiles of Vitis vinifera L. cvs 'Cabernet franc' (CF) and 'Chardonnay' (CH) berries in two consecutive years. The experimental vineyard was located in Jiaodong Peninsula of China, which is characterized by a temperate monsoon-type climate and relatively short sunlight duration. Clusters located in the interior of the canopy received less sunlight irradiation than the exterior positions, and the average temperature around clusters located in different positions differed slightly. The results showed that over two years, the positions of clusters in the canopy had no consistent impact on cluster weight, berry weight, juice total soluble solids or titratable acidity for either cultivar. For both cultivars, the interior clusters had lower total flavonol concentrations than the exterior clusters, while the position of clusters in the canopy had no major impacts on the composition of anthocyanins and flavan-3-ols. The volatile compounds were somewhat influenced by the positions of clusters in the canopy, while some bound norisoprenoids and terpenoids had lower levels in interior clusters than in exterior clusters. These results will help winegrowers make decisions regarding harvest strategies.

Combined Metabolite and Transcriptome Profiling Reveals the Norisoprenoid Responses in Grape Berries to Abscisic Acid and Synthetic Auxin

The abscisic acid (ABA) increase and auxin decline are both indicators of ripening initiation in grape berry, and norisoprenoid accumulation also starts at around the onset of ripening. However, the relationship between ABA, auxin, and norisoprenoids remains largely unknown, especially at the transcriptome level. To investigate the transcriptional and posttranscriptional regulation of the ABA and synthetic auxin 1-naphthaleneacetic acid (NAA) on norisoprenoid production, we performed time-series GC-MS and RNA-seq analyses on Vitis vinifera L. cv. Cabernet Sauvignon grape berries from pre-veraison to ripening. Higher levels of free norisoprenoids were found in ABA-treated mature berries in two consecutive seasons, and both free and total norisoprenoids were significantly increased by NAA in one season. The expression pattern of known norisoprenoid-associated genes in all samples and the up-regulation of specific alternative splicing isoforms of VviDXS and VviCRTISO in NAA-treated berries were predicted to contribute to the norisoprenoid accumulation in ABA and NAA-treated berries. Combined weighted gene co-expression network analysis (WGCNA) and DNA affinity purification sequencing (DAP-seq) analysis suggested that VviGATA26, and the previously identified switch genes of myb RADIALIS (VIT_207s0005g02730) and MAD-box (VIT_213s0158g00100) could be potential regulators of norisoprenoid accumulation. The positive effects of ABA on free norisoprenoids and NAA on total norisoprenoid accumulation were revealed in the commercially ripening berries. Since the endogenous ABA and auxin are sensitive to environmental factors, this finding provides new insights to develop viticultural practices for managing norisoprenoids in vineyards in response to changing climates.

Influence of attenuated reflected solar radiation from the vineyard floor on volatile compounds in Cabernet Sauvignon grapes and wines of the north foot of Mt. Tianshan

In this study, fruit-zone microclimate was modified by three treatments, including inter-row mulch (M), the combination of leaf removal applied at the onset of veraison and inter-row mulch (MLR-BV), and the combination of leaf removal applied at complete veraison and inter-row mulch (MLR-EV), in a semi-arid climate in three consecutive years (2015-2017). M decreased fruit-zone reflected solar radiation from vineyard floor and low temperature (10-20 °C) duration, whereas it increased soil temperature and high temperature (> 30 °C) duration. MLR-BV and MLR-EV increased fruit-zone incident photosynthetically active radiation while decreased the duration of 20-25 °C compared to M. Notably, M significantly decreased grape total norisoprenoid concentrations in 2015-2017, and total terpenoid concentrations in 2015-2016. Applying leaf removal applied at the onset of veraison could compensate the decreases of total norisoprenoids and terpenoids caused by M when two treatments were applied together. Besides, M significantly increased grape total C₆/C₉ compound concentrations, besides, (Z)-3-hexen-1-ol concentrations were significantly higher in grapes of M than those of MLR-BV in 2015-2017. Light exposure and high temperature duration after veraison had strong positive correlations with total norisoprenoids and terpenoids, besides, low temperature duration was positively correlated with total norisoprenoids. In addition, light exposure after veraison had strong negative correlations with total C₆/C₉ compounds. With respect to the volatile compounds in wines, M significantly decreased the concentrations of isopentanol and ethyl acetate, and the concentrations of ethyl cinnamate, phenylacetaldehyde, phenylethyl alcohol and 3-methylthio-1-propanol were significantly lower in MLR-BV and MLR-EV than in M. The outcome of this study can assist winegrowers to properly adjust vineyard managements to optimize the concentrations of desired volatile compounds in grapes and wines.

Bioinformatics Resources for Plant Abiotic Stress Responses: State of the Art and Opportunities in the Fast Evolving -Omics Era

Abiotic stresses are among the principal limiting factors for productivity in agriculture. In the current era of continuous climate changes, the understanding of the molecular aspects involved in abiotic stress response in plants is a priority. The rise of -omics approaches provides key strategies to promote effective research in the field, facilitating the investigations from reference models to an increasing number of species, tolerant and sensitive genotypes. Integrated multilevel approaches, based on molecular investigations at genomics, transcriptomics, proteomics and metabolomics levels, are now feasible, expanding the opportunities to clarify key molecular aspects involved in responses to abiotic stresses. To this aim, bioinformatics has become fundamental for data production, mining and integration, and necessary for extracting valuable information and for comparative efforts, paving the way to the modeling of the involved processes. We provide here an overview of bioinformatics resources for research on plant abiotic stresses, describing collections from -omics efforts in the field, ranging from raw data to complete databases or platforms, highlighting opportunities and still open challenges in abiotic stress research based on -omics technologies.