The grapevine VviPrx31 peroxidase as a candidate gene involved in anthocyanin degradation in ripening berries under high temperature

Grapevine varieties show different sensitivities to flavonoid alterations caused by high temperatures under two irrigation conditions

This study aimed to assess the response of four red grapevine (Vitis vinifera L.) varieties to elevated temperature, drought and their combination, focusing on the concentration and profile of grape flavonoids. Fruit-bearing cuttings of Tempranillo, Cabernet Sauvignon, Merlot and Grenache grew in greenhouses under, either ambient temperature (T) or ambient temperature + 4 °C (T+4). Plants also received either full irrigation (FI, substrate field capacity) or deficit irrigation (DI, 50 % substrate field capacity). In general, T+4 decreased the concentration of anthocyanins, but DI mitigated this effect. T+4 and DI increased the abundance of methylated anthocyanins and flavonols with additive effects. Grapes under T+4 had higher abundance of acylated anthocyanins, while DI increased the proportion of tri-hydroxylated anthocyanins and flavonols. The impact of interacting elevated temperature and drought on grape composition was genotype dependent. In terms of anthocyanin concentration and profile, Tempranillo was the most affected variety, whereas Grenache was less sensitive.

Phenolic profile, antioxidant capacity and oxidoreductase enzyme activity in autochthonous grape varieties from Bosnia and Herzegovina

The variability of phenolic compounds among grape varieties has an important role in selecting winemaking techniques, but the use of phenolic profiles for quality control is still fragmented and incomplete. Given the recent climate change and global warming, biochemical characterisation of secondary metabolites in autochthonous grape varieties is a very important factor for their preservation and sustainable agriculture. Two autochthonous grape varieties from the western Herzegovina region in Bosnia and Herzegovina have been selected for the research targeting at the evaluation of their phenolic profiles, antioxidant activities, and the correlation with oxidoreductase enzymes polyphenol oxidase and Class III peroxidase, in different berry tissues. The obtained results indicate a similar qualitative profile of phenolic compounds in exocarp and mesocarp in both varieties, but their concentrations and antioxidant activity vary significantly. The correlation between phenolic compounds and oxidoreductase enzyme activities in different grape berry tissues is discussed in this article.

Combined Metabolome and Transcriptome Analysis Revealed the Accumulation of Anthocyanins in Grape Berry (Vitis vinifera L.) under High-Temperature Stress

In grape (Vitis vinifera L.) cultivation, high temperatures (HTs) usually reduce the accumulation of anthocyanins. In order to elucidate the regulatory mechanism of anthocyanin biosynthesis under high-temperature environments, we investigated the effects of HT stress at veraison (5% coloring of grape ears) on fruit coloration and anthocyanin biosynthesis in 'Summer Black' (XH) and 'Flame seedless' (FL) grapevines. Compared to the control group (35 °C), the total anthocyanin content of XH and FL grapes subjected to a high-temperature (HT) treatment group (40 °C) decreased significantly as the HT treatment continued, but showed an upward trend with fruit development. However, the concentration of procyanidins increased significantly following HT treatment but decreased with fruit development. Nonetheless, FL grapes showed some resistance to the HT condition, producing anthocyanin content at ripeness comparable to the control group, demonstrating a greater adaptability to HT conditions than XH grapes. Based on the CIRG index, at stage S4, the fruit of FL was classified as dark red, while XH was classified as blue-black in the control group. Anthocyanin-targeted metabonomics identified eight different types of anthocyanins accumulating in the peels of XH and FL grapes during ripening, including cyanidins, delphinidins, malvidins, pelargonidins, peonidins, petunidins, procyanidins, and flavonoids. Malvidins were the most abundant in the two grape varieties, with malvidin-3-O-glucoside being more sensitive to high temperatures. HT treatment also down-regulated the expression of structural genes and regulators involved in the anthocyanin synthesis pathways. We used the WGCNA method to identify two modules that were significantly correlated with total anthocyanin and procyanidin contents. Among them, MYBCS1, bHLH137, WRKY65, WRKY75, MYB113-like, bZIP44, and GST3 were predicted to be involved in grape anthocyanin biosynthesis. In conclusion, this study conducted in-depth research on the HT inhibition of the biosynthesis of anthocyanins in XH and FL grapes, for reference.

Napa Valley Cabernet Sauvignon Proanthocyanidin Changes During Fruit Ripening: A Multi-Appellation Survey

In 2015, an experiment was designed to investigate the distribution and variance of in winegrape flavonoids across the ripening phase in the Napa Valley. This Cabernet Sauvignon experiment was intended to evaluate the polyphenol differences across Napa Valley in order to understand parameters controlling "proanthocyanidin activity." This method has shown promise in understanding proanthocyanidin (PA) astringency based on size distribution, pigmentation, conformation, and composition. Results from whole berry partial extractions showed that seed PA material was driving PA activity early in the ripening phase, while the formation of the pigmented polymer led to a decrease later in the growing season. Multivariate analysis showed that the main drivers of changes across the ripening phase were the molecular masses of PAs and the amount of pigmentation. Given the high amount of variability seen in the experiment between sites in such a small geographical area, the results suggest that manipulation of PA activity may be possible in the vineyard, perhaps explaining variations in wine mouthfeel attributes between locations. These results can be used to develop furthermore controlled experiments targeting the variables responsible for PA activity changes.

For a Colorful Life: Recent Advances in Anthocyanin Biosynthesis during Leaf Senescence

Leaf senescence is the last stage of leaf development, and it is accompanied by a leaf color change. In some species, anthocyanins are accumulated during leaf senescence, which are vital indicators for both ornamental and commercial value. Therefore, it is essential to understand the molecular mechanism of anthocyanin accumulation during leaf senescence, which would provide new insight into autumn coloration and molecular breeding for more colorful plants. Anthocyanin accumulation is a surprisingly complex process, and significant advances have been made in the past decades. In this review, we focused on leaf coloration during senescence. We emphatically discussed several networks linked to genetic, hormonal, environmental, and nutritional factors in regulating anthocyanin accumulation during leaf senescence. This paper aims to provide a regulatory model for leaf coloration and to put forward some prospects for future development.

Use of an automatic fruit-zone cooling system to cope with multiple summer stresses in Sangiovese and Montepulciano grapes

Grapevines are frequently subjected to heatwaves and limited water availability during ripening. These conditions can have consequences for the physiological health of the vines. Moreover, the situation is often exacerbated by intense solar radiation, resulting in reduced yield due to sunburn and a decline in quality. In light of these challenges, our study aimed to develop a fruit-zone cooling system designed to mitigate grape sunburn damage and improve the microclimate conditions within the vineyard. The system comprises a network of proximal sensors that collect microclimate data from the vineyard and an actuator that activates nebulizers when the temperature exceeds the threshold of 35°C. The research was conducted over two years (2022 and 2023) in Bologna (Italy) using potted Sangiovese and Montepulciano vines. These two vintages were characterized by high temperatures, with varying amounts of rainfall during the test period, significantly impacting the evaporative demand, which was notably higher in 2023. Starting from the veraison stage we compared three treatments: Irrigated control vines (WW); Control vines subjected to 50% water restriction during the month of August (WS); WS vines treated with nebulized water in the bunch area during the stress period (WS+FOG). The application of nebulized water effectively reduced the temperature of both the air around the clusters and the clusters themselves. As we expected, Montepulciano showed better single leaf assimilation rate and stomatal conductance under non-limiting water conditions than Sangiovese while their behavior was unaffected under water-scarce conditions. Importantly, for the first time, we demonstrated that nebulized water positively affected gas exchange in both grape varieties. In addition to this, the vines treated with the misting system exhibited higher productivity compared to WS vines without affecting technological maturity. In the 2023 vintage, the activation of the system prevented the ripening blockage that occurred in Montepulciano under water stress. Regarding the concentration of total anthocyanins, a significant increase in color was observed in WS+FOG treatment, suggesting a predominant role of microclimate on anthocyanin biosynthesis and reduction of oxidative phenomena. In conclusion, the fruit-zone cooling system proved to be an invaluable tool for mitigating the adverse effects of multiple summer stresses.

Vineyard microclimate alterations induced by black inter-row mulch through transcriptome reshaped the flavoromics of cabernet sauvignon grapes

BACKGROUND

Weed control is essential for agricultural floor management in vineyards and the inter-row mulching is an eco-friendly practice to inhibit weed growth via filtering out photosynthetically active radiation. Besides weed suppression, inter-row mulching can influence grapevine growth and the accumulation of metabolites in grape berries. However, the complex interaction of multiple factors in the field challenges the understanding of molecular mechanisms on the regulated metabolites. In the current study, black geotextile inter-row mulch (M) was applied for two vintages (2016-2017) from anthesis to harvest. Metabolomics and transcriptomics analysis were conducted in two vintages, aiming to provide insights into metabolic and molecular responses of Cabernet Sauvignon grapes to M in a semi-arid climate.

RESULTS

Upregulation of genes related to photosynthesis and heat shock proteins confirmed that M weakened the total light exposure and grapes suffered heat stress, resulting in lower sugar-acid ratio at harvest. Key genes responsible for enhancements in phenylalanine, glutamine, ornithine, arginine, and C6 alcohol concentrations, and the downward trend in ε-viniferin, anthocyanins, flavonols, terpenes, and norisoprenoids in M grapes were identified. In addition, several modules significantly correlated with the metabolic biomarkers through weighted correlation network analysis, and the potential key transcription factors regulating the above metabolites including VviGATA11, VviHSFA6B, and VviWRKY03 were also identified.

CONCLUSION

This study provides a valuable overview of metabolic and transcriptomic responses of M grapes in semi-arid climates, which could facilitate understanding the complex regulatory network of metabolites in response to microclimate changes.

Longer cluster hanging time decreases the impact of grapevine red blotch disease in Vitis vinifera L. Merlot across two seasons

BACKGROUND

Grapevine red blotch virus (GRBV) is a recently discovered virus and a major concern for the wine industry. Prior research indicated that GRBV delays grape ripening by reducing °Brix and anthocyanin concentrations in grapes from infected vines, resulting in higher ethanol concentrations in wines made from healthy fruit compared to diseased vines, which have an impact on sensory properties. In this study, infected fruit (Vitis vinifera L. Merlot) was sequentially harvested (in 2016 and 2017) and chaptalized (in 2017) to ameliorate the impact of GRBV on grape and final wine composition.

RESULTS

Chemical parameters including phenolic and volatile profiles of grapes and their subsequent wines were measured. Sensory properties were determined by descriptive analyses. Results demonstrated that GRBV decreased sugar accumulation and anthocyanin synthesis in grapes. Wines from GRBV grapes harvested at later ripening stage produced wines that were more similar chemically and sensorially to wines made from healthy fruit than to wines made from GRBV fruit harvested earlier.

CONCLUSION

A longer hang time of GRBV grapes is a potential strategy to mitigate the impacts of GRBV. However, chaptalization of diseased fruit must was inefficient at increasing similarities to wines made from healthy fruit. © 2023 Society of Chemical Industry.

Effect of applied shading during fruit ripening on tannin structure-activity relationships of grape skin extracts

BACKGROUND

Historically, the effect of wine grape shading on flavonoids has investigated the impact of light incidence on proanthocyanidin (PA), flavonol, or anthocyanin concentration. In addition to concentration, the current experiment was designed to look at changes in PA composition, size and tannin activity through ripening. Tannin activity is a methodology for assessing the impact of structure and size on the affinity of tannin towards a hydrophobic surface and is considered to be a proxy for predicted astringency descriptive quality. In 2016 a shade cloth study was imposed on Cabernet Sauvignon on Mt Veeder, within the larger Napa Valley viticultural area. A control, which was unshaded, and two treatments consisting of 40% and 80% shade were applied at the onset of veraison.

RESULTS

Results showed significant differences in the composition and concentration of anthocyanins throughout ripening. Compositional differences in PA were also observed, where shaded treatments had a significantly higher proportion of galloylated subunits. The molecular mass of the extracted tannin was significantly lower in the unshaded control than in the 80% shade treatment. These factors led to a lower measured tannin activity in extracts from exposed fruit.

CONCLUSION

This work suggests that manipulation of canopy architecture, such as artificial shading, leads to changes in berry pigmentation, tannin composition and activity. These results show that the astringency and mouthfeel characteristics of a wine may be altered by vineyard management practices. © 2023 Society of Chemical Industry.

AcMYB10 Involved in Anthocyanin Regulation of 'Hongyang' Kiwifruit Induced via Fruit Bagging and High-Postharvest-Temperature Treatments

Light and temperature are key factors influencing the accumulation of anthocyanin in fruit crops. To assess the effects of fruit bagging during development and high post-ripening temperature on 'Hongyang' kiwifruit, we compared the pigmentation phenotypes and expression levels of anthocyanin-related genes between bagged and unbagged treatments, and between 25 °C and 37 °C postharvest storage temperatures. Both the bagging and 25 °C treatments showed better pigmentation phenotypes with higher anthocyanin concentrations. The results of the qRT-PCR analysis revealed that the gene expression levels of LDOX (leucoanthocyanidin dioxygenase), F3GT (UDP-flavonoid 3-O-glycosyltransferase ), AcMYB10, and AcbHLH42 were strongly correlated and upregulated by both the bagging treatment and 25 °C storage. The results of bimolecular fluorescence complementation and luciferase complementation imaging assays indicated an interaction between AcMYB10 and AcbHLH42 in plant cells, whereas the results of a yeast one-hybrid assay further demonstrated that AcMYB10 activated the promoters of AcLODX and AcF3GT. These results strongly suggest that enhanced anthocyanin synthesis is caused by the promoted expression of AcLODX and AcF3GT, regulated by the complex formed by AcMYB10-AcbHLH42.

The role of environmental stress in fruit pigmentation

For many fruit crops, the colour of the fruit outwardly defines its eating quality. Fruit pigments provide reproductive advantage for the plant as well as providing protection against unfavourable environmental conditions and pathogens. For consumers these colours are considered attractive and provide many of the dietary benefits derived from fruits. In the majority of species, the main pigments are either carotenoids and/or anthocyanins. They are produced in the fruit as part of the ripening process, orchestrated by phytohormones and an ensuing transcriptional cascade, culminating in pigment biosynthesis. Whilst this is a controlled developmental process, the production of pigments is also attuned to environmental conditions such as light quantity and quality, availability of water and ambient temperature. If these factors intensify to stress levels, fruit tissues respond by increasing (or ceasing) pigment production. In many cases, if the stress is not severe, this can have a positive outcome for fruit quality. Here, we focus on the principal environmental factors (light, temperature and water) that can influence fruit colour.

Model-assisted analysis for tuning anthocyanin composition in grape berries

Anthocyanin composition is responsible for the red colour of grape berries and wines, and contributes to their organoleptic quality. However, anthocyanin biosynthesis is under genetic, developmental and environmental regulation, making its targeted fine-tuning challenging. We constructed a mechanistic model to simulate the dynamics of anthocyanin composition throughout grape ripening in Vitis vinifera, employing a consensus anthocyanin biosynthesis pathway. The model was calibrated and validated using six datasets from eight cultivars and 37 growth conditions. Tuning the transformation and degradation parameters allowed us to accurately simulate the accumulation process of each individual anthocyanin under different environmental conditions. The model parameters were robust across environments for each genotype. The coefficients of determination (R2) for the simulated versus observed values for the six datasets ranged from 0.92 to 0.99, while the relative root mean square errors (RRMSEs) were between 16.8 and 42.1 %. The leave-one-out cross-validation for three datasets showed R2 values of 0.99, 0.96 and 0.91, and RRMSE values of 28.8, 32.9 and 26.4 %, respectively, suggesting a high prediction quality of the model. Model analysis showed that the anthocyanin profiles of diverse genotypes are relatively stable in response to parameter perturbations. Virtual experiments further suggested that targeted anthocyanin profiles may be reached by manipulating a minimum of three parameters, in a genotype-dependent manner. This model presents a promising methodology for characterizing the temporal progression of anthocyanin composition, while also offering a logical foundation for bioengineering endeavours focused on precisely adjusting the anthocyanin composition of grapes.

Modeling purple basil, sage, spearmint, and sweet basil responses to daily light integral and mean daily temperature

Mean daily temperature (MDT) and daily light integral (DLI) can interact to influence growth and development of plants. Our objectives were to determine 1) the extent DLI and MDT influence growth and development of purple basil 'Dark Opal' (Ocimum basilicum), sage 'Extrakta' (Salvia officinalis), spearmint 'Spanish' (Mentha spicata), and sweet basil 'Nufar' (Ocimum basilicum) and 2) the influence on purple basil color. Young plants were transplanted into hydroponic systems in five greenhouse compartments with MDT set points of 23, 26, 29, 32, or 35°C and DLIs from 5 to 19 mol·m‒2·d‒1, respectively. At harvest, growth, development, and leaf color was measured. Branch number of all genera increased as MDT increased from ~23 to 35°C. Sweet basil branch number increased as DLI increased from 5.5 to 13.2 mol·m‒2·d‒1, but the effect of DLI was attenuated as MDT decreased. In contrast, increasing DLI from ~5-6 to ~18-19 mol·m‒2·d‒1 increased sage and spearmint branch number more when MDT was lower (~23°C) compared to ~35°C, while branch number of purple basil was not influenced by DLI. The optimal MDT (MDTopt) for sage and spearmint fresh mass decreased from 27.5 to 23.5°C and from 30.4 to 27.8°C, respectively, as DLI increased from 6 to 18 mol·m‒2·d‒1, while sweet basil fresh mass MDTopt increased from 32.6 to 35.5°C as DLI increased from 6 to 11 mol·m‒2·d‒1. Purple basil was greener [hue angle (h°) = 99° to 138°] when MDT was ~35°C regardless of DLI, but when MDT was lower (~25°C), basil was more purple (h° = 335°) at a DLI of 18.7 compared to 5.0 mol·m‒2·d‒1 (h° = 98°). Taken together, MDT and DLI can have a large impact on plant growth, development, and color and can be manipulated to achieve desired characteristics.

Impact of Climate Change on Altered Fruit Quality with Organoleptic, Health Benefit, and Nutritional Attributes

As a consequence of global climate change, acute water deficit conditions, soil salinity, and high temperature have been on the rise in their magnitude and frequency, which have been found to impact plant growth and development negatively. However, recent evidence suggests that many fruit plants that face moderate abiotic stresses can result in beneficial effects on the postharvest storage characters of the fruits. Salinity, drought, and high temperature conditions stimulate the synthesis of abscisic acid (ABA), and secondary metabolites, which are vital for fruit quality. The secondary metabolites like phenolic acids and anthocyanins that accumulate under abiotic stress conditions have antioxidant activity, and therefore, such fruits have health benefits too. It has been noticed that fruits accumulate more sugar and anthocyanins owing to upregulation of phenylpropanoid pathway enzymes. The novel information that has been generated thus far indicates that the growth environment during fruit development influences the quality components of the fruits. But the quality depends on the trade-offs between productivity, plant defense, and the frequency, duration, and intensity of stress. In this review, we capture the current knowledge of the irrigation practices for optimizing fruit production in arid and semiarid regions and enhancement in the quality of fruit with the application of exogenous ABA and identify gaps that exist in our understanding of fruit quality under abiotic stress conditions.

Temperature variability during the growing season affects the quality attributes of table grapes in Pothwar-insight from a new emerging viticulture region in South Asia

Rising air temperature due to climate change has posed a mammoth challenge to global viticulture and key berry quality traits are compromised. Exploring the effects of seasonal temperature variability on berry ripening and quality attributes in different viticulture regions may help in sustainable viticulture industry. The present research was designed to explore the effect of temperature variables on key quality attributes of table grape cultivars in Pothwar region of Pakistan. Key berry quality traits such as total soluble solids (TSS), titratable acidity (TA), maturity indices (MI), ascorbic acid, sugars, total polyphenol contents (TPC) and total anthocyanin contents (TAC) were unlocked for four important table grape cultivars under varying environmental conditions at Chakwal and Islamabad districts for two consecutive vintages of 2019 and 2020. The district Chakwal has up to 0.92 °C, 1.35 °C, 1.12°C and 0.81°C higher Tmin, Tmax, Tmean and diurnal temperature variation (DTV) respectively, compared to Islamabad particularly for the 2019 vintage. The results of the present study revealed that the warmer site (Chakwal) has significantly (P ≤0.05) higher juice pH, TSS (°brix) and maturity indices (MI) particularly for the relatively hotter vintage of 2019. Interestingly, MI was 33% higher for the relatively warmer vintage of 2019 compared to 2020 with relatively lower acidity (up to 38%). Moreover, higher titratable acidity (11.2%), ascorbic acid (28.5%), polyphenols (20.3%) and anthocyanins (10.6%) were noticed for the colder Islamabad compared to Chakwal. Although elevated temperature for warmer location and vintage favoured berry ripening, however key biochemical attributes such as titratable acidity, ascorbic acid, polyphenols and anthocyanins were negatively affected. The findings of the present research provide useful insight into the impact of growing season temperature on key berry attributes and may help devise adaptation strategies to improve berry quality.

Temperature differences between sites lead to altered phenylpropanoid metabolism in a varietal dependent manner

Elevated temperature has already caused a significant loss of wine growing areas and resulted in inferior fruit quality, particularly in arid and semi-arid regions. The existence of broad genetic diversity in V. vinifera is key in adapting viticulture to climate change; however, a lack of understanding on the variability in berry metabolic response to climate change remains a major challenge to build ad-hoc strategies for quality fruit production. In the present study, we examined the impact of a consistent temperature difference between two vineyards on polyphenol metabolism in the berries of 20 red V. vinifera cultivars across three consecutive seasons (2017-2019). The results emphasize a varietal specific response in the content of several phenylpropanoid metabolites; the interaction factor between the variety and the vineyard location was also found significant. Higher seasonal temperatures were coupled with lower flavonol and anthocyanin contents, but such reductions were not related with the level of expression of phenylpropanoid related genes. Hierarchical clustering analyses of the metabolic data revealed varieties with a location specific response, exceptional among them was Tempranillo, suggesting a greater susceptibility to temperature of this cultivar. In conclusion, our results indicate that the extensive genetic capacity of V. vinifera bears a significant potential to withstand temperature increase associated with climate change.

Evaluation of the Effect of Preharvest Melatonin Spraying on Fruit Quality of 'Yuluxiang' Pear Based on Principal Component Analysis

Melatonin (MT), an indoleamine compound, has a pleiotropic effect on plant growth and development and can regulate the quality of tree fruit. Systematic research on the effect of preharvest MT spraying on pear fruit quality and technical solutions for MT application to regulate pear fruit quality are still lacking. Thus, here we aimed to evaluate the effects of different spraying times, concentrations, and exogenous MT application times on 'Yuluxiang' pear fruit quality. Our results showed that the single fruit weight and vertical and horizontal diameters of pear fruit sprayed with MT twice at 30 and 90 d after full bloom were the largest, and the red and green values of the treatment were the highest. MT-treated pears had higher contents of total soluble solids, soluble sugar, sucrose, sorbitol, fructose, and glucose and lower contents of titratable acid, malic acid, and citric acid. Moreover, exogenous MT treatment increased the pear peel strength. Based on the principal component analysis of 10 fruit quality indices, the suitable periods for MT spraying on 'Yuluxiang' pears were 30 and 90 d after full bloom, the suitable concentration was 100 μmol/L, and the suitable number of times was two. This study provides a theoretical reference for optimizing MT application and improving pear fruit quality.

Investigating the impact of pedoclimatic conditions on the oenological performance of two red cultivars grown throughout southern Italy

The cultivated grapevine, Vitis vinifera subsp. vinifera, possesses a rich biodiversity with numerous varieties. Each variety adapts differently to varying pedoclimatic conditions, which greatly influence the terroir expression of wine regions. These conditions impact vine growth, physiology, and berry composition, ultimately shaping the unique characteristics and typicity of the wines produced. Nowadays, the potential of the different adaptation capacities of grape varieties has not yet been thoroughly investigated. We addressed this issue by studying two grape varieties, Aglianico and Cabernet Sauvignon, in two different pedoclimatic conditions of Southern Italy. We evaluated and compared the effect of different pedoclimatic conditions on plant physiology, the microbial quality of grapes using Next-Generation Sequencing (NGS) technology, the expression trends of key genes in ripe berries and the concentration of phenolic compounds in grapes and wines by HPLC-MS, HPLC-DAD, NMR and spectrophotometric analyses. Metabolomic and microbiome data were integrated with quantitative gene expression analyses to examine varietal differences and plasticity of genes involved in important oenological pathways. The data collected showed that the phenotypic response of studied grapes in terms of vigor, production, and fruit quality is strongly influenced by the pedoclimatic conditions and, in particular, by soil physical properties. Furthermore, Aglianico grape variety was more influenced than the Cabernet Sauvignon by environmental conditions. In conclusion, the obtained findings not only reinforce the terroir concept and our comprehension of grape's ability to adapt to climate variations but can also have implications for the future usage of grape genetic resources.

Crop forcing technique and irrigation strategy modified the content and phenolic profile of cv. Tempranillo grape berries grown in a semi-arid climate

BACKGROUND

Climate change modifies the content and phenolic profiles of grapes and wines. It is known that high temperatures, related to climate change, reduce anthocyanins and procyanidin (catechin and tannin) compounds accumulated in the berries. In recent years, with the aim of improving the phenolic composition of the berries, the technique of crop forcing has been proposed to delay grape ripening to a more favourable period of temperatures.

RESULTS

In this study, crop forcing was applied to cv. Tempranillo vines on two different dates, after flowering (F1) and after fruit set (F2), and compared to a treatment control (NF, without forcing). Additionally, as a secondary factor, two irrigation strategies were established in each treatment: irrigation with no water stress, and a pre-veraison deficit irrigation. The study was carried out in three consecutive years (2017-2019). For most of the parameters analysed, no interaction was found. Therefore, for these parameters, the effect of each of these techniques was investigated independently. Regardless of the irrigation strategy, F2 berries achieved higher contents of catechins and anthocyanins than NF berries. Each year, regardless of the irrigation strategy, crop forcing increased the content of monoglucoside forms, and had a positive effect on the total content of malvidin, petunidin, delphinidin, peonidin and malvidin derivatives, but only affected acetyl and coumaryl forms in 2017. However, the effect of irrigation strategy was less significant and consistent, being more dependent on the vintage.

CONCLUSION

Regardless of vine water status, crop forcing technique applied after fruit set could be used by vine growers to delay ripening of the grapes and thus achieve an increase in the anthocyanin characteristics of the grapes. © 2023 Society of Chemical Industry.

Glutathione to ameliorate growth criterions and chemical constituents of geranium irrigated with salt water

Essential oil of geranium (Pelargonium graveolensL) has biological activities that make it used in food and pharmaceutical manufactures. High salinity is one of the factors that lead to lack of expansion in the production of medicinal and aromatic plants, especially in the new reclaimed soil located at arid and semi arid regions. Glutathione is a natural antioxidant that can help plants to withstand unfavorable environmental conditions such as the salinity of irrigation water. This trial aimed to diminish the undesirable effect of exposure to irrigation with salt water on geranium herbs through subjected them to exogenous application of glutathione. Geranium plants were irrigated with various concentrations of salt water with sodium chloride (0.0, 34.2, 51.3, and 68.4 mM) without (0 mg/L) or with glutathione (375 mg/L). Plants exposed to various rates of saline irrigation water with glutathione resulted in higher values of growth criterions (fresh and dry aerial parts), photosynthetic pigments, carbohydrates, protein, proline, essential oil (% or yield), antioxidant enzymes (peroxidase and superoxide dismutase), nitrogen, phosphorous, potassium, calcium, iron, zinc, manganese and copper than those subjected to saline irrigation water without glutathione. Higher amounts were found in sodium and chloride of plant treated with saline irrigation water than those treated saline irrigation water with glutathione. It may be summarized that productivity of geranium plants can be improved with adapting them under saline irrigation conditions by adding glutathione. This trial benefits the producers of geranium to alleviate the hurtful effects of salinity in reclaimed regions with adding glutathione.

How Extracellular Reactive Oxygen Species Reach Their Intracellular Targets in Plants

Reactive oxygen species (ROS) serve as secondary messengers that regulate various developmental and signal transduction processes, with ROS primarily generated by NADPH OXIDASEs (referred to as RESPIRATORY BURST OXIDASE HOMOLOGs [RBOHs] in plants). However, the types and locations of ROS produced by RBOHs are different from those expected to mediate intracellular signaling. RBOHs produce O2•- rather than H2O2 which is relatively long-lived and able to diffuse through membranes, and this production occurs outside the cell instead of in the cytoplasm, where signaling cascades occur. A widely accepted model explaining this discrepancy proposes that RBOH-produced extracellular O2•- is converted to H2O2 by superoxide dismutase and then imported by aquaporins to reach its cytoplasmic targets. However, this model does not explain how the specificity of ROS targeting is ensured while minimizing unnecessary damage during the bulk translocation of extracellular ROS (eROS). An increasing number of studies have provided clues about eROS action mechanisms, revealing various mechanisms for eROS perception in the apoplast, crosstalk between eROS and reactive nitrogen species, and the contribution of intracellular organelles to cytoplasmic ROS bursts. In this review, we summarize these recent advances, highlight the mechanisms underlying eROS action, and provide an overview of the routes by which eROS-induced changes reach the intracellular space.

The Effect of Netting Bags on the Postharvest Quality, Bioactive and Nutritional Compounds, and the Spoilage Microorganisms Content of Bell Peppers

The packaging nets used for bell peppers act as a form of protection. However, the manufacturing is based on polymers that cause serious environmental problems. The effects of nets made of biodegradable materials, such as poly(lactic) acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), and cactus stem residues, were evaluated on four different colors of 'California Wonder' bell peppers stored over a 25-day storage period under controlled and ambient temperature conditions. Compared to commercial polyethylene nets, the bell peppers kept in the biodegradable nets did not show notable differences with respect to color, weight loss, total soluble solids, and titratable acidity. However, there were significant differences (p < 0.05) in terms of phenol content, carotenoids (orange bell peppers), anthocyanins, and vitamin C, with an overall tendency to show a higher content in those kept in PLA 60%/PBTA 40%/cactus stem flour 3% compared to commercial packaging. In addition, the same net notably reduced the development of bacteria, fungi, and yeasts during the storage of red, orange, and yellow bell peppers. As postharvest packaging for bell peppers, this net could be considered a viable option for the storage of this product.

Global transcriptome and gene co-expression network analyses reveal regulatory and non-additive effects of drought and heat stress in grapevine

Despite frequent co-occurrence of drought and heat stress, the molecular mechanisms governing plant responses to these stresses in combination have not often been studied. This is particularly evident in non-model, perennial plants. We conducted large scale physiological and transcriptome analyses to identify genes and pathways associated with grapevine response to drought and/or heat stress during stress progression and recovery. We identified gene clusters with expression correlated to leaf temperature and water stress and five hub genes for the combined stress co-expression network. Several differentially expressed genes were common to the individual and combined stresses, but the majority were unique to the individual or combined stress treatments. These included heat-shock proteins, mitogen-activated kinases, sugar metabolizing enzymes, and transcription factors, while phenylpropanoid biosynthesis and histone modifying genes were unique to the combined stress treatment. Following physiological recovery, differentially expressed genes were found only in plants under heat stress, both alone and combined with drought. Taken collectively, our results suggest that the effect of the combined stress on physiology and gene expression is more severe than that of individual stresses, but not simply additive, and that epigenetic chromatin modifications may play an important role in grapevine responses to combined drought and heat stress.

Genetic diversity and local adaption of alfalfa populations (Medicago sativa L.) under long-term grazing

Genomic information on alfalfa adaptation to long-term grazing is useful for alfalfa genetic improvement. In this study, 14 alfalfa populations were collected from long-term grazing sites (> 25 years) across four soil zones in western Canada. Alfalfa cultivars released between 1926 and 1980 were used to compare degree of genetic variation of the 14 populations. Six agro-morphological and three nutritive value traits were evaluated from 2018 to 2020. The genotyping-by-sequencing (GBS) data of the alfalfa populations and environmental data were used for genotype-environment association (GEA). Both STRUCTURE and UPGMA based on 19,853 SNPs showed that the 14 alfalfa populations from long-term grazing sites had varying levels of parentages from alfalfa sub-species Medicago sativa and M. falcata. The linear regression of STRUCTURE membership probability on phenotypic data indicated genetic variations of forage dry matter yield, spring vigor and plant height were low, but genetic variations of regrowth, fall plant height, days to flower and crude protein were still high for the 14 alfalfa populations from long-term grazing sites. The GEA identified 31 SNPs associated with 13 candidate genes that were mainly associated with six environmental factors of. Candidate genes underlying environmental factors were associated with a variety of proteins, which were involved in plant responses to abiotic stresses, i.e., drought, cold and salinity-alkali stresses.

Diverse Physiological Roles of Flavonoids in Plant Environmental Stress Responses and Tolerance

Flavonoids are characterized as the low molecular weight polyphenolic compounds universally distributed in planta. They are a chemically varied group of secondary metabolites with a broad range of biological activity. The increasing amount of evidence has demonstrated the various physiological functions of flavonoids in stress response. In this paper, we provide a brief introduction to flavonoids' biochemistry and biosynthesis. Then, we review the recent findings on the alternation of flavonoid content under different stress conditions to come up with an overall picture of the mechanism of involvement of flavonoids in plants' response to various abiotic stresses. The participation of flavonoids in antioxidant systems, flavonoid-mediated response to different abiotic stresses, the involvement of flavonoids in stress signaling networks, and the physiological response of plants under stress conditions are discussed in this review. Moreover, molecular and genetic approaches to tailoring flavonoid biosynthesis and regulation under abiotic stress are addressed in this review.

Natural variations of HSFA2 enhance thermotolerance in grapevine

Heat stress limits growth and development of crops including grapevine which is a popular fruit in the world. Genetic variability in crops thermotolerance is not well understood. We identified and characterized heat stress transcription factor HSFA2 in heat sensitive Vitis vinifera 'Jingxiu' (named as VvHSFA2) and heat tolerant Vitis davidii 'Tangwei' (named as VdHSFA2). The transcriptional activation activities of VdHSFA2 are higher than VvHSFA2, the variation of single amino acid (Thr315Ile) in AHA1 motif leads to the difference of transcription activities between VdHSFA2 and VvHSFA2. Based on 41 Vitis germplasms, we found that HSFA2 is differentiated at coding region among heat sensitive V. vinifera, and heat tolerant Vitis davidii and Vitis quinquangularis. Genetic evidence demonstrates VdHSFA2 and VvHSFA2 are positive regulators in grape thermotolerance, and the former can confer higher thermotolerance than the latter. Moreover, VdHSFA2 can regulate more target genes than VvHSFA2. As a target gene of both VdHSFA2 and VvHSFA2, overexpression of MBF1c enhanced the grape thermotolerance whereas dysfunction of MBF1c resulted in thermosensitive phenotype. Together, our results revealed that VdHSFA2 confers higher thermotolerance than VvHSFA2, and MBF1c acts as their target gene to induce thermotolerance. The VdHSFA2 may be adopted for molecular breeding in grape thermotolerance.

Prospecting the Resilience of Several Spanish Ancient Varieties of Red Grape under Climate Change Scenarios

BACKGROUND

Climate change results in warmer air temperatures and an uncertain amount and distribution of annual precipitations, which will directly impact rainfed crops, such as the grapevine. Traditionally, ancient autochthones grapevine varieties have been substituted by modern ones with higher productivity. However, this homogenization of genotypes reduces the genetic diversity of vineyards which could make their ability to adapt to challenges imposed by future climate conditions difficult. Therefore, this work aimed to assess the response of four ancient grapevine varieties to high temperatures under different water availabilities, focusing on plant water relations, grape technological and phenolic maturity, and the antioxidant capacity of the must.

METHODS

The study was conducted on fruit-bearing cuttings grown in pots in temperature-gradient greenhouses. A two-factorial design was established where two temperature regimes, ambient and elevated (ambient + 4 °C), were combined with two water regimes, full irrigation and post-veraison deficit irrigation, during fruit ripening.

RESULTS

There were significant differences among the ancient varieties regarding plant water relations and fruit quality.

CONCLUSION

This research underlines the importance of evaluating the behavior of ancient grapevine varieties that could offer good options for the adaptation of viticulture to future climate conditions.

A recessive mutation in muscadine grapes causes berry color-loss without influencing anthocyanin pathway

Anthocyanins, a major class of flavonoids, are important pigments of grape berries. Despite the recent discovery of the genetic cause underlying the loss of color, the metabolomic and molecular responses are unknown. Anthocyanin quantification among diverse berry color muscadines suggests that all genotypes could produce adequate anthocyanin quantities, irrespective of berry color. Transcriptome profiling of contrasting color muscadine genotypes proposes a potential deficiency that occurs within the anthocyanin transport and/or degradation mechanisms and might cause unpigmented berries. Genome-wide association studies highlighted a region on chromosome-4, comprising several genes encoding glutathione S-transferases involved in anthocyanin transport. Sequence comparison among genotypes reveals the presence of two GST4b alleles that differ by substituting the conserved amino acid residue Pro₁₇₁-to-Leu. Molecular dynamics simulations demonstrate that GST4b2–Leu₁₇₁ encodes an inactive protein due to modifications within the H-binding site. Population genotyping suggests the recessive inheritance of the unpigmented trait with a GST4b2/2 homozygous. A model defining colorless muscadines’ response to the mutation stimulus, avoiding the impact of trapped anthocyanins within the cytoplasm is established.

Transcriptome profiling and mutational analysis suggest a potential deficiency in anthocyanin transport by glutathione S-transferases and/or degradation mechanisms that might cause unpigmented berries.

Lily WRKY factor LlWRKY22 promotes thermotolerance through autoactivation and activation of LlDREB2B

Most of WRKY transcription factors play important roles in plant development, protection against disease, and response to abiotic stress; however, their roles in lily are largely unknown. Transcriptome analysis in lily (Lilium longiflorum) led to the identification and isolation of a WRKY-IIe gene, LlWRKY22, which was found to be activated at high temperature and play a positive role in thermotolerance regulation. LlWRKY22 expression was continuously activated by heat stress. We further found that LlWRKY22 protein localized to the nucleus and exhibited transactivation activity in both yeast and plant cells, and that its C terminus contributed to its transactivation activity. Meanwhile, overexpression of LlWRKY22 in lily improved thermotolerance and activated the expression of heat-related LlDREB2B gene; however, silencing of LlWRKY22 exerted the opposite effects. Further analysis revealed that LlWRKY22 directly activated the expression of LlDREB2B by binding to two tandem W-box elements on its promoter. Simultaneously, we also found that LlWRKY22 can directly bind its own promoter, thereby activating its own expression and forming a positive regulatory loop. Combined, our findings demonstrated that LlWRKY22 may be a new regulator of heat stress response and positively participates in the establishment of thermotolerance by activating itself and LlDREB2B.

Light Intensity- and Spectrum-Dependent Redox Regulation of Plant Metabolism

Both light intensity and spectrum (280–800 nm) affect photosynthesis and, consequently, the formation of reactive oxygen species (ROS) during photosynthetic electron transport. ROS, together with antioxidants, determine the redox environment in tissues and cells, which in turn has a major role in the adjustment of metabolism to changes in environmental conditions. This process is very important since there are great spatial (latitude, altitude) and temporal (daily, seasonal) changes in light conditions which are accompanied by fluctuations in temperature, water supply, and biotic stresses. The blue and red spectral regimens are decisive in the regulation of metabolism because of the absorption maximums of chlorophylls and the sensitivity of photoreceptors. Based on recent publications, photoreceptor-controlled transcription factors such as ELONGATED HYPOCOTYL5 (HY5) and changes in the cellular redox environment may have a major role in the coordinated fine-tuning of metabolic processes during changes in light conditions. This review gives an overview of the current knowledge of the light-associated redox control of basic metabolic pathways (carbon, nitrogen, amino acid, sulphur, lipid, and nucleic acid metabolism), secondary metabolism (terpenoids, flavonoids, and alkaloids), and related molecular mechanisms. Light condition-related reprogramming of metabolism is the basis for proper growth and development of plants; therefore, its better understanding can contribute to more efficient crop production in the future.

Identification of Candidate Genes Responsible for Flower Colour Intensity in Gentiana triflora

Gentians cultivated in Japan (Gentiana triflora and Gentiana scabra and hybrids) have blue flowers, but flower colour intensity differs among cultivars. The molecular mechanism underlying the variation in flower colour intensity is unclear. Here, we produced F₂ progeny derived from an F₁ cross of intense- and faint-blue lines and attempted to identify the genes responsible for flower colour intensity using RNA-sequencing analyses. Comparative analysis of flower colour intensity and transcriptome data revealed differentially expressed genes (DEGs), although known flavonoid biosynthesis-related genes showed similar expression patterns. From quantitative RT-PCR (qRT-PCR) analysis, we identified two and four genes with significantly different expression levels in the intense- and faint-blue flower lines, respectively. We conducted further analyses on one of the DEGs, termed GtMIF1, which encodes a putative mini zinc-finger protein homolog, which was most differently expressed in faint-blue individuals. Functional analysis of GtMIF1 was performed by producing stable tobacco transformants. GtMIF1-overexpressing tobacco plants showed reduced flower colour intensity compared with untransformed control plants. DNA-marker analysis also confirmed that the GtMIF1 allele of the faint-blue flower line correlated well with faint flower colour in F₂ progeny. These results suggest that GtMIF1 is one of the key genes involved in determining the flower colour intensity of gentian.

Climate Change Effects on Grapevine Physiology and Biochemistry: Benefits and Challenges of High Altitude as an Adaptation Strategy

Grapevine berry quality for winemaking depends on complex and dynamic relationships between the plant and the environment. Winemakers around the world are demanding a better understanding of the factors that influence berry growth and development. In the last decades, an increment in air temperature, CO₂ concentration and dryness occurred in wine-producing regions, affecting the physiology and the biochemistry of grapevines, and by consequence the berry quality. The scientific community mostly agrees in a further raise as a result of climate change during the rest of the century. As a consequence, areas most suitable for viticulture are likely to shift into higher altitudes where mean temperatures are suitable for grape cultivation. High altitude can be defined as the minimum altitude at which the grapevine growth and development are differentially affected. At these high altitudes, the environments are characterized by high thermal amplitudes and great solar radiations, especially ultraviolet-B (UV-B). This review summarizes the environmental contribution of global high altitude-related climatic variables to the grapevine physiology and wine composition, for a better evaluation of the possible establishment of vineyards at high altitude in climate change scenarios.

Color fading in lotus (Nelumbo nucifera) petals is manipulated both by anthocyanin biosynthesis reduction and active degradation

Flower color is a key trait that determines the ornamental quality of aquatic lotus (Nelumbo nucifera). Color fading significantly decreases the ornamental value of lotus flowers. However, the molecular mechanism underlying lotus petal discoloration remains largely unknown. Here, the anthocyanin content and global transcriptional profiling of lotus petals of cultivar 'Qiusanse' in four developmental stages were analyzed. Five anthocyanin components were detected, and the total anthocyanin content decreased as the petal color changed from red to nearly white. Moreover, the malondialdehyde (MDA) content and peroxidase (POD) activity increased during color fading. RNA-seq analysis revealed a total of 4,092 differentially expressed genes (DEGs) between petal developmental stages. Notably, oxidoreductase and hydrolase activity related genes were overrepresented in DEGs. The expression pattern of key anthocyanin biosynthesis genes including, CHS, F3H, ANS, UFGT, and transcription factor regulators, including MYBs, WRKYs and bHLHs were correlated with anthocyanin accumulation. Interestingly, DEGs associated with anthocyanin degradation and vacuolar pH regulation, including peroxidase, proton pumps regulators such as WRKY3 and MYB5-like, were significantly upregulated during the late stages of flowering. This study reveals for the first time the transcriptional dynamics during lotus petal discoloration. Our results suggest the involvement of anthocyanin biosynthesis repressors and degrading genes as well as pH regulators in controlling color fading of lotus petals. The study also provides valuable information and candidate genes for improving the lotus flower color.

High Temperature Alters Anthocyanin Concentration and Composition in Grape Berries of Malbec, Merlot, and Pinot Noir in a Cultivar-Dependent Manner

Climate is determinant for grapevine geographical distribution, berry attributes, and wine quality. Due to climate change, a 2−4 °C increase in mean diurnal temperature is predicted by the end of the century for the most important Argentine viticulture region. We hypothesize that such temperature increase will affect color intensity and other quality attributes of red grapes and wines. The present study investigated the effect of high temperature (HT) on anthocyanin concentration and composition, pH, and resveratrol and solids content in berries of three major wine-producing varieties during fruit ripening in two seasons. To this end, a structure that increased mean diurnal temperature by 1.5−2.0 °C at berry sites, compared to Control (C) plants grown without such structure, was implemented in field grown vineyards of Malbec, Merlot, and Pinot Noir. Results revealed a cultivar-dependent response to HT conditions, with Malbec and Pinot Noir berries exhibiting significant decreases in total anthocyanin concentration (TAC) at veraison and harvest, respectively, while Merlot maintained an unaffected pigment content under HT. The decrease in TAC was associated with reduced levels of delphinidin, cyanidin, petunidin, peonidin, and malvidin glycosides, and increased ratios of acylated (AA)/non-acylated anthocyanins (NAA), suggesting pigment acylation as a possible stress-response mechanism for attenuating HT negative effects. Under HT, Pinot Noir, which does not produce AA, was the only cultivar with lower TAC at harvest (p < 0.05). pH, resveratrol, and solids content were not affected by HT. Our results predict high, medium, and low plasticity with regard to color quality attributes for Malbec, Merlot, and Pinot Noir, respectively, in the context of climate change.

Genome-Wide Characterization and Anthocyanin-Related Expression Analysis of the B-BOX Gene Family in Capsicum annuum L

The transcription factors, B-box (BBX), belong to a subfamily of the zinc finger family of proteins and exhibit multiple biological functions in plant growth, development, and abiotic stress response pathways. In this study, a total of 23 CaBBX members were identified using the pepper reference genome database. According to the gene structure, conserved domains, and the phylogenetic tree, 23 CaBBX genes were divided into four groups, wherein the analysis of the promoter region indicated the presence of cis-acting elements related to plant development, hormones, and stress response. Interspecies collinearity analysis showed that the CaBBXs had three duplicated gene pairs, and the highest gene density was found on chromosomes 2 and 7. Transcriptome RNA-seq data and quantitative polymerase chain reaction (qRT-PCR) analysis of pepper plants spanning the entire period showed that more than half of the CaBBX genes were widely expressed in diversity tissues of pepper. Co-expression network analysis indicated that the CaBBXs and the anthocyanin structural genes had a close co-expression relationship. Thus, it was reasonably speculated that the CaBBX genes may be involved in the regulation of anthocyanin biosynthesis. Overall, this study involved the genome-wide characterization of the CaBBX family and may serve as a solid foundation for further investigations on CaBBX genes involved in the anthocyanin synthesis mechanisms and development in pepper.

Biosynthesis and regulation of anthocyanin pathway genes

Anthocyanins are the phenolic compounds responsible for coloring pigments in fruits and vegetables. Anthocyanins offer a wide range of health benefits to human health. Their scope has expanded dramatically in the past decade, making anthocyanin control, influx, and outflow regulation fascinating for many researchers. The main culprit is anthocyanin stability and concentration form, which demands novel ways because these are critical in the food industry. This review aims to examine anthocyanin synthesis via triggering transcription genes that code for anthocyanin-producing enzymes. The balance between production and breakdown determines anthocyanin accumulation. Thus, increasing the anthocyanin content in food requires the stability of molecules in the vacuolar lumen, the pigment fading process, and a better understanding of the mechanism. The promising option is biosynthesis by metabolically engineered microorganisms with a lot of success. This study aims to look into and evaluate the existing literature on anthocyanin production, namely the biosynthesis of anthocyanin pathway genes, production by microbial cell factories, and the regulatory factors that can modulate the production of anthocyanins. Understanding these mechanisms will provide new biotechnological approaches.Key points• Factors affecting the regulation of anthocyanins• Focus on degradation, biosynthesis pathway genes, and alternative systems for the production of anthocyanins• Microbial cell factories can be used to produce large amounts of anthocyanins.

Foliar application of kaolin and zeolites to adapt the adverse effects of climate change in Vitis vinifera L. cv. Sangiovese

One of the first effects of climate change in wine-growing areas is the advancement of phenological stages, especially concerning early berry ripening. In this condition, the decoupling between technological and phenolic maturity often occurs. Anthocyanins in red grapes are among the compounds that mostly contribute to phenolic maturity. However, their accumulation in the grape berries is known to be impaired by high temperatures. Therefore, this study aims to evaluate the efficacy of mineral-based compounds treatments with kaolin and zeolite, based on chabasite, on the enhancement of anthocyanins accumulation, also at the molecular level, analysing the gene expressions along the flavonoid biosynthesis pathway during ripening of Sangiovese berries. In addition, the temperature of berries and grape leaves, vine water status, leaf photosynthetic efficiency, total soluble solids, titratable acidity and pH were measured throughout the growing season. Hence, in the current study, it has been demonstrated the efficacy of kaolin and zeolite treatments not only in lowering the daily maximum grape berries temperature but also in the improvement of grapes anthocyanins accumulation correlated with the enhancement of expression of those genes involved in their biosynthesis pathway. Moreover, treatments had no significant effect on productive parameters.

Plant Flavonoids in Mediterranean Species: A Focus on Flavonols as Protective Metabolites under Climate Stress

Flavonoids are specialized metabolites largely widespread in plants where they play numerous roles including defense and signaling under stress conditions. These compounds encompass several chemical subgroups such as flavonols which are one the most represented classes. The most studied flavonols are kaempferol, quercetin and myricetin to which research attributes antioxidative properties and a potential role in UV-defense through UV-screening mechanisms making them critical for plant adaptation to climate change. Despite the great interest in flavonol functions in the last decades, some functional aspects remain under debate. This review summarizes the importance of flavonoids in plant defense against climate stressors and as signal molecules with a focus on flavonols in Mediterranean plant species. The review emphasizes the relationship between flavonol location (at the organ, tissue and cellular scales) and their function as defense metabolites against climate-related stresses. It also provides evidence that biosynthesis of flavonols, or flavonoids as a whole, could be a crucial process allowing plants to adapt to climate change, especially in the Mediterranean area which is considered as one of the most sensitive regions to climate change over the globe.

Anthocyanin stability and degradation in plants

Anthocyanins, a flavonoid group of polyphenolic compounds, have evolved in plants since the land was colonized by plants. These bioactive compounds play critical roles in diverse physiological processes. They are synthesized in the cytosol and transported into the vacuole for storage or to other destinations, where they function as bioactive molecules. The mechanisms of anthocyanin synthesis and transport have been well studied. However, the precise regulation of the mechanisms of anthocyanin degradation remains to be elucidated. In this review, we highlight recent progress in the understanding of the characteristics and functions of anthocyanins and class III peroxidases, as well as of the existing evidence of the effects of class III peroxidases on the degradation of anthocyanins and the possible regulatory mechanisms involved.

Natural and Synthetic Flavylium-Based Dyes: The Chemistry Behind the Color

Flavylium compounds are a well-known family of pigments because they are prevalent in the plant kingdom, contributing to colors over a wide range from shades of yellow-red to blue in fruits, flowers, leaves, and other plant parts. Flavylium compounds include a large variety of natural compound classes, namely, anthocyanins, 3-deoxyanthocyanidins, auronidins, and their respective aglycones as well as anthocyanin-derived pigments (e.g., pyranoanthocyanins, anthocyanin-flavan-3-ol dimers). During the past few decades, there has been increasing interest among chemists in synthesizing different flavylium compounds that mimic natural structures but with different substitution patterns that present a variety of spectroscopic characteristics in view of their applications in different industrial fields. This Review provides an overview of the chemistry of flavylium-based compounds, in particular, the synthetic and enzymatic approaches and mechanisms reported in the literature for obtaining different classes of pigments, their physical-chemical properties in relation to their pH-dependent equilibria network, and their chemical and enzymatic degradation. The development of flavylium-based systems is also described throughout this Review for emergent applications to explore some of the physical-chemical properties of the multistate of species generated by these compounds.

Characterisation of the class III peroxidase gene family in carrot taproots and its role in anthocyanin and lignin accumulation

Plant class III peroxidases (CIII Prxs) are involved in numerous essential plant life processes, such as plant development and differentiation, lignification and seed germination, and defence against pathogens. However, there is limited information about the structure-function relationships of Prxs in carrots. This study identified 75 carrot peroxidases (DcPrxs) and classified them into seven subgroups based on phylogenetic analysis. Gene structure analysis revealed that these DcPrxs had between one and eight introns, while conserved motif analysis showed a typical motif composition and arrangement for CIII Prx. In addition, eighteen tandem duplication events, but only eight segmental duplications, were identified among these DcPrxs, indicating that tandem duplication was the main contributor to the expansion of this gene family. Histochemical analyses showed that lignin was mainly localised in the cell walls of xylem, and Prx activity was determined in the epidermal region of taproots. The xylem always showed higher lignin concentration and lower Prx activity compared to the phloem in the taproots of both carrot cultivars. Combining these observations with RNA sequencing, some Prx genes were identified as candidate genes related to lignification and pigmentation. Three peroxidases (DcPrx30, DcPrx32, DcPrx62) were upregulated in the phloem of both genotypes. Carrot taproots are an attractive resource for natural food colourants and this study elucidated genome-wide insights of Prx for the first time, developing hypotheses concerning their involvement with lignin and anthocyanin in purple carrots. The findings provide an essential foundation for further studies of Prx genes in carrot, especially on pigmentation and lignification mechanisms.

The Complexity of Modulating Anthocyanin Biosynthesis Pathway by Deficit Irrigation in Table Grapes

Deficit irrigation (DI) is an irrigation scheduling technique that is used in grapes to improve red color development; however, results are not always satisfactory in table grapes. The red color in grapes is mainly due to the plant pigment anthocyanin. In the present study, the anthocyanin biosynthesis in Scarlet Royal grapes (Vitis vinifera L.) grown in the San Joaquin and Coachella Valleys, and subjected to two different DI strategies was investigated. The objective of this study was to identify potential regulatory factors that may lead to potential treatments to improve red color in table grapes, especially under warm climate conditions. In both locations, DI induced the expression of several genes involved in three major pathways that control the red color in table grapes: anthocyanin biosynthesis, hormone biosynthesis, and antioxidant system. DI at veraison induced anthocyanin accumulation and enhanced red color in berries at harvest time. However, anthocyanin accumulation was lower at the Coachella Valley compared to the San Joaquin Valley. The lower level of anthocyanin was associated with lower expression of critical genes involved in anthocyanin biosynthesis, such as flavonoid-3-O-glucosyltransferase (UFGT), myb-related regulatory gene (R2R3-MYB) (MYBA1), basic helix-loop-helix (bHLH) (MYCA1) and the tryptophan-aspartic acid repeat (WDR or WD40) proteins (WDR1). Further, gene expression analysis revealed the association of ABA biosynthesis gene 9-cis-epoxycarotenoid dioxygenase (NCED1), 1-aminocyclopropane-1-carboxylic acid oxidase (ACO3), and the gibberellic acid (GA) catabolic gene GA2 oxidase (GA2ox1) in the induction of anthocyanin biosynthesis. An increase in the chalcone synthase gene (CHS2) was observed in response to DI treatments in both sites. However, CHS2 expression was higher in Coachella Valley after ending the DI treatment, suggesting the involvement of environmental stress in elevating its transcripts. This data was also supported by the lower level of antioxidant gene expression and enzyme activities in the Coachella Valley compared to the San Joaquin Valley. The present data suggested that the lack of grape red coloration could partially be due to the lower level of antioxidant activities resulting in accelerated anthocyanin degradation and impaired anthocyanin biosynthesis. It seems that under challenging warmer conditions, several factors are required to optimize anthocyanin accumulation via DI, including an active antioxidant system, proper light perception, and hormonal balance.

Phenolic Characterization of Cabernet Sauvignon Wines From Different Geographical Indications of Mendoza, Argentina: Effects of Plant Material and Environment

The chemical and sensory characteristics of the wines are related to the geographical origin of the grape, as a result of the interplay between the plant material (G), its acclimatization to the environment (E) and the human factor that influences both the vineyard and the winery. The range of phenotypes that a single genotype can express depending on its environment is known as phenotypic plasticity and is the result of G × E interaction. The present study evaluated the independent and interactive effects of Cabernet Sauvignon plant materials (G: Clone 7 and Mount Eden) implanted in different geographical indications of Mendoza, Argentina (E: Agrelo, Pampa El Cepillo, Altamira and Gualtallary) according to fruit yield and phenolic profiles of wines. The experiment was carried out during 2018 and 2019 vintages using a multifactorial design. When berries reached 24 °Brix, the clusters were harvested, analyzed and wines elaborated by a standardized procedure. Then, the anthocyanin and non-anthocyanin phenolic profiles of wines were determined by high-performance liquid chromatography with diode array and fluorescence detection (HPLC-DAD–FLD). The results revealed significant G × E interactions for yield traits, including the number of clusters per plant. Differential chemical composition and quality parameters of the resulting wines, markedly affected by E, were observed; that is the geographical location of the vineyards. There were similarities in the phenolic composition between Pampa El Cepillo and Altamira, while larger differences between Agrelo and Gualtallary were observed. Gualtallary presented the highest levels of anthocyanins, quercetin and trans-resveratrol. The increased amount of these compounds in Gualtallary was associated with an increased UV-B exposure of plants at this high altitude environment. This is the first report that characterizes the effects of plant material and environment for Cabernet Sauvignon. These results are of oenological and viticulture interest for the wine industry demonstrating that the selection of the plant material and the vineyard location for Cabernet Sauvignon can considerably affect the quality attributes of wines.

Metabolomics-Based Evaluation of Crop Quality Changes as a Consequence of Climate Change

Fruit composition determines the fruit quality and, consequently, consumer acceptance. As fruit quality can be modified by environmental conditions, it will be impacted by future alterations produced by global warming. Therefore, agricultural activities will be influenced by the changes in climatological conditions in cultivable areas, which could have a high socioeconomic impact if fruit production and quality decline. Currently, different stresses are being applied to several cultivated species to evaluate their impact on fruit metabolism and plant performance. With the use of metabolomic tools, these changes can be precisely measured, allowing us to determine changes in the patterns of individual compounds. As these changes depend on both the stress severity and the specific species involved and even on the specific cultivar, individual analysis must be conducted. To date, the most-studied crops have mainly been crops that are widely cultivated and have a high socioeconomic impact. In the near future, with the development of these metabolomic strategies, their implementation will be extended to other species, which will allow the adaptation of cultivation conditions and the development of varieties with high adaptability to climatological changes.

OsTTG1, a WD40 repeat gene, regulates anthocyanin biosynthesis in rice

Anthocyanins play an important role in the growth of plants, and are beneficial to human health. In plants, the MYB-bHLH-WD40 (MBW) complex activates the genes for anthocyanin biosynthesis. However, in rice, the WD40 regulators remain to be conclusively identified. Here, a crucial anthocyanin biosynthesis gene was fine mapped to a 43.4-kb genomic region on chromosome 2, and a WD40 gene OsTTG1 (Oryza sativa TRANSPARENT TESTA GLABRA1) was identified as ideal candidate gene. Subsequently, a homozygous mutant (osttg1) generated by CRISPR/Cas9 showed significantly decreased anthocyanin accumulation in various rice organs. OsTTG1 was highly expressed in various rice tissues after germination, and it was affected by light and temperature. OsTTG1 protein was localized to the nucleus, and can physically interact with Kala4, OsC1, OsDFR and Rc. Furthermore, a total of 59 hub transcription factor genes might affect rice anthocyanin biosynthesis, and LOC_Os01g28680 and LOC_Os02g32430 could have functional redundancy with OsTTG1. Phylogenetic analysis indicated that directional selection has driven the evolutionary divergence of the indica and japonica OsTTG1 alleles. Our results suggest that OsTTG1 is a vital regulator of anthocyanin biosynthesis, and an important gene resource for the genetic engineering of anthocyanin biosynthesis in rice and other plants.

Improved genome assembly and pan-genome provide key insights into eggplant domestication and breeding

Eggplant (Solanum melongena L.) is an important horticultural crop and one of the most widely grown vegetables from the Solanaceae family. It was domesticated from a wild, prickly progenitor carrying small, round, non-anthocyanic fruits. We obtained a novel, highly contiguous genome assembly of the eggplant '67/3' reference line, by Hi-C retrofitting of a previously released short read- and optical mapping-based assembly. The sizes of the 12 chromosomes and the fraction of anchored genes in the improved assembly were comparable to those of a chromosome-level assembly. We resequenced 23 accessions of S. melongena representative of the worldwide phenotypic, geographic, and genetic diversity of the species, and one each from the closely related species Solanum insanum and Solanum incanum. The eggplant pan-genome contained approximately 51.5 additional megabases and 816 additional genes compared with the reference genome, while the pan-plastome showed little genetic variation. We identified 53 selective sweeps related to fruit color, prickliness, and fruit shape in the nuclear genome, highlighting selection leading to the emergence of present-day S. melongena cultivars from its wild ancestors. Candidate genes underlying the selective sweeps included a MYBL1 repressor and CHALCONE ISOMERASE (for fruit color), homologs of Arabidopsis GLABRA1 and GLABROUS INFLORESCENCE STEMS2 (for prickliness), and orthologs of tomato FW2.2, OVATE, LOCULE NUMBER/WUSCHEL, SUPPRESSOR OF OVATE, and CELL SIZE REGULATOR (for fruit size/shape), further suggesting that selection for the latter trait relied on a common set of orthologous genes in tomato and eggplant.

In through the out door: Biochemical mechanisms affecting flavonoid glycoside catabolism in plants

Plants are the sole source of flavonoids, a chemical category that includes flavonols. For the most part, flavonols occur as glycosides with numerous postulated biological roles in plants, including photoprotection, modulation of hormone translocation, and sequestration of reactive oxygen species. Flavonol glycosides are often considered as dead-end metabolites because related flavonoids (i.e., anthocyanins) occur in terminal tissues such as flowers and fruit, but recent evidence points to their turnover in planta, including developing photosynthetic tissues. Although microbial degradation pathways for flavonol glycosides of plant origin are well described, plant catabolic pathways are little studied by comparison. This review will address our current understanding of biochemical processes leading to the loss of flavonol glycosides in plants, with a specific emphasis on the evidence for flavonol-specific β-glucosidases. Complete elucidation of these catabolic pathways is dependent on the identification of regiospecific modifying steps, including enzymes associated with the hydrolysis of rhamnosylated flavonols, as well as flavonol peroxidation and their encoding genes. Herein, we highlight challenges for the identification of hypothetical plant α-rhamnosidases and peroxidases involved in flavonol glycoside degradation, and the potential biological role of this catabolism in mitigating oxidative stress in developing and postharvest plant tissues.

Effects of Defoliation at Fruit Set on Vine Physiology and Berry Composition in Cabernet Sauvignon Grapevines

Grapevine canopy defoliation is a fundamentally important technique for the productivity and quality of grapes. Leaf removal is a pivotal operation on high-density vines which aims to improve air circulation, light exposure, and leaf gas exchange. The effects of leaf removal (LR) on vine physiology and berry composition in Cabernet Sauvignon grapevines were studied during the 2018–2019 growing season in the Bolgheri area, Tuscany, Italy. The basal leaves were removed at fruit set at two severity levels (removal of four basal leaves of each shoot (LR4) and removal of eight basal leaves (LR8)). The two treatments were compared with the not defoliated control (CTRL). The following physiological parameters of vines were measured: leaf gas exchange, leaf water potential, chlorophyll fluorescence and indirect chlorophyll content. The results showed that defoliation increased single leaf photosynthesis. In addition, qualitative grape parameters (phenolic and technological analyses) and daytime and night-time berry temperature were studied. The results showed that leaf removal had an impact on total soluble solids (°Brix), titratable acidity, and pH. The LR8-treated grapes had higher titratable acidity, while those in the LR4 treatment had higher °Brix and extractable anthocyanin and polyphenol content. Berry weight was not significantly influenced by the timing and severity of basal defoliation. Therefore, this research aims to investigate the effects of defoliation at the fruit set on vines performance.