24-epibrassinolide enhances drought tolerance in grapevine (Vitis vinifera L.) by regulating carbon and nitrogen metabolism.

KEY MESSAGE: Exogenous application of 24-epibrassinolide can alleviate oxidative damage, improve photosynthetic capacity, and regulate carbon and nitrogen assimilation, thus improving the tolerance of grapevine (Vitis vinifera L.) to drought stress. Brassinosteroids (BRs) are a group of plant steroid hormones in plants and are involved in regulating plant tolerance to drought stress. This study aimed to investigate the regulation effects of BRs on the carbon and nitrogen metabolism in grapevine under drought stress. The results indicated that drought stress led to the accumulation of superoxide radicals and hydrogen peroxide and an increase in lipid peroxidation. A reduction in oxidative damage was observed in EBR-pretreated plants, which was probably due to the improved antioxidant concentration. Moreover, exogenous EBR improved the photosynthetic capacity and sucrose phosphate synthase activity, and decreased the sucrose synthase, acid invertase, and neutral invertase, resulting in improved sucrose (190%) and starch (17%) concentrations. Furthermore, EBR pretreatment strengthened nitrate reduction and ammonium assimilation. A 57% increase in nitrate reductase activity and a 13% increase in glutamine synthetase activity were observed in EBR pretreated grapevines. Meanwhile, EBR pretreated plants accumulated a greater amount of proline, which contributed to osmotic adjustment and ROS scavenging. In summary, exogenous EBR enhanced drought tolerance in grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

Emerging roles of brassinosteroids and light in anthocyanin biosynthesis and ripeness of climacteric and non-climacteric fruits.

Anthocyanins are important pigments that contribute to fruit quality. The regulation of anthocyanin biosynthesis by several transcription factors via sophisticated regulatory networks has been studied in various plants. Brassinosteroids (BRs), a new class of plant hormone, are involved in regulating anthocyanin biosynthesis in fruits. Furthermore, light directly affects the synthesis and distribution of anthocyanins. Here, we summarize the recent progress toward understanding the impact of BR and light on anthocyanin biosynthesis in climacteric and non-climacteric fruits. We review the BR and light signaling pathways and highlight the important transcription factors that are associated with the synthesis of anthocyanins, such as BZR1 (brassinazole-resistant 1, BR signaling pathway), HY5 (elongated hypocotyl 5) and COP1 (constitutively photomorphogenic 1, light signal transduction pathway), which bind with the target genes involved in anthocyanin synthesis. In addition, we review the mechanism by which light signals interact with hormonal signals to regulate anthocyanin biosynthesis.

Effect of ammonium and nitrate supplies on nitrogen and sucrose metabolism of Cabernet Sauvignon (Vitis vinifera cv.).

BACKGROUND: The quality of wine is highly dependent on the quality of berries. Development of berries is influenced by the type and ratio of different nitrogen supplies in the soil. To understand the impact of varying sources and levels of nitrate and ammonium on sucrose and nitrogen metabolism of Vitis vinifera cv. Cabernet Sauvignon, we tested nutrient solutions with four NO3 - -N:NH4 + -N ratios (100:0, 75:25, 50:50, 0:100) through the root system. RESULTS: The form and quantity of nitrogen affected berries and leaves with source-sink relationships. Soluble sugar levels were significantly higher in plants treated with mixed nitrogen sources (75:25 and 50:50) compared to single nitrogen sources (100:0 and 0:100). In particular, treating plants with mixed nitrogen source at a 75:25 ratio resulted in 22% higher fructose levels in berries compared to the 50:50 treatment. In addition, mixed nitrogen treatments resulted in significantly higher amino acid levels and protein content. Mixed nitrogen substrates also increased the expression of enzymes involved in both nitrogen and sucrose metabolism. CONCLUSION: Plants did not maximize the nitrogen supply when single form nitrogen was provided, and the mixed nitrogen substrates consistently increased the amount of available carbon and nitrogen in the berries and leaves. We found that NO3 - -N:NH4 + -N ratio of 75:25 was the optimum formula for improving nitrogen and sucrose metabolism, and reducing the competition between nitrogen and sucrose. By examining the nutrient utilization of plants cultivated with different nitrogen forms, the present study provides insights into improving cultivation and production practices. © 2020 Society of Chemical Industry.

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

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

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

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

Tissue-Specific Expression Analysis of Anthocyanin Biosynthetic Genes in White- and Red-Fleshed Grape Cultivars.

Yan73, a teinturier (dyer) grape variety in China, is one of the few Vitis vinifera cultivars with red-coloured berry flesh. To examine the tissue-specific expression of genes associated with berry colour in Yan73, we analysed the differential accumulation of anthocyanins in the skin and flesh tissues of two red-skinned grape varieties with either red (Yan73) or white flesh (Muscat Hamburg) based on HPLC-MS analysis, as well as the differential expression of 18 anthocyanin biosynthesis genes in both varieties by quantitative RT-PCR. The results revealed that the transcripts of GST, OMT, AM3, CHS3, UFGT, MYBA1, F3'5'H, F3H1 and LDOX were barely detectable in the white flesh of Muscat Hamburg. In particular, GST, OMT, AM3, CHS3 and F3H1 showed approximately 50-fold downregulation in the white flesh of Muscat Hamburg compared to the red flesh of Yan73. A correlation analysis between the accumulation of different types of anthocyanins and gene expression indicated that the cumulative expression of GST, F3'5'H, LDOX and MYBA1 was more closely associated with the acylated anthocyanins and the 3'5'-OH anthocyanins, while OMT and AM3 were more closely associated with the total anthocyanins and methoxylated anthocyanins. Therefore, the transcripts of OMT, AM3, GST, F3'5'H, LDOX and MYBA1 explained most of the variation in the amount and composition of anthocyanins in skin and flesh of Yan73. The data suggest that the specific localization of anthocyanins in the flesh tissue of Yan73 is most likely due to the tissue-specific expression of OMT, AM3, GST, F3'5'H, LDOX and MYBA1 in the flesh.

Promoting effect of foliage sprayed zinc sulfate on accumulation of sugar and phenolics in berries of Vitis vinifera cv. Merlot growing on zinc deficient soil.

The effect of foliage sprayed zinc sulfate on berry development of Vitis vinifera cv. Merlot growing on arid zone Zn-deficient soils was investigated over two consecutive seasons, 2013 and 2014. Initial zinc concentration in soil and vines, photosynthesis at three berry developmental stages, berry weight, content of total soluble solids, titratable acidity, phenolics and expression of phenolics biosynthetic pathway genes throughout the stages were measured. Foliage sprayed zinc sulfate showed promoting effects on photosynthesis and berry development of vines and the promotion mainly occurred from veraison to maturation. Zn treatments enhanced the accumulation of total soluble solids, total phenols, flavonoids, flavanols, tannins and anthocyanins in berry skin, decreasing the concentration of titratable acidity. Furthermore, foliage sprayed zinc sulfate could significantly influence the expression of phenolics biosynthetic pathway genes throughout berry development, and the results of expression analysis supported the promotion of Zn treatments on phenolics accumulation. This research is the first comprehensive and detailed study about the effect of foliage sprayed Zn fertilizer on grape berry development, phenolics accumulation and gene expression in berry skin, providing a basis for improving the quality of grape and wine in Zn-deficient areas.

Effect of Three Training Systems on Grapes in a Wet Region of China: Yield, Incidence of Disease and Anthocyanin Compositions of Vitis vinifera cv. Cabernet Sauvignon.

Grapevine training systems determine the suitability for grape varieties in a specific growing region. We evaluated the influence of three training systems, Single Guyot (SG), Spur-pruned Vertical Shoot-Positioned (VSP), and Four-Arm Kniffin (4AK), on the performance of grapes and vines of Vitis vinifera L. cv. Cabernet Sauvignon in the 2012 and 2013 growing seasons in a wet region of central China. 4AK was the most productive system in comparison to SG and VSP. SG and VSP had lower disease infections of leaves and berries, especially in the mid- and final stage of berry ripening. Three training systems had no impact on berry maturity. PLS-DA (Partial Least Squares-Discriminant) analysis showed that the relatively dry vintage could well discriminate three training systems, but the wet vintage was not. A wet vintage of 2013 had more accumulation of 3'5'-substituted and acylated anthocyanins, including malvidin-3-O-(6-O-acetyl)-glucoside, malvidin-3-O-glucoside, and petunidin-3-O-(cis-6-O-coumaryl)-glucoside, etc. With regard to the effect of training systems, 4AK grapes had the lowest concentrations of total anthocyanins and individual anthocyanins, SG and VSP differed according to the different vintages, and showed highest concentration of total individual anthocyanins in 2012 and 2013, respectively. Generally, VSP benefited the most, contributing to significantly highest levels of total individual anthocyanins, and major anthocyanin, including malvidin-3-O-glucoside and malvidin-3-O-(6-O-acetyl)-glucoside, and the grapes obtained from VSP presented significantly highest proportion of 3'5'-substituted anthocyanins. With regard to the ratios of 3'5'/3'-substituted, methoxylated/non-methoxylated and acylated/non-acylated anthocyanins, the significantly higher levels were also shown in VSP system. In summary, VSP was the best training system for Cabernet Sauvignon to accumulate relatively stable individual anthocyanins in this wet region of China and potentially in other rainy regions.

The ameliorative effects of exogenous melatonin on grape cuttings under water-deficient stress: antioxidant metabolites, leaf anatomy, and chloroplast morphology.

Grapes are an important economic crop and are widely cultivated around the world. Most grapes are grown in arid or semi-arid regions, and droughts take a heavy toll in grape and wine production areas. Developing effective drought-resistant cultivation measures is a priority for viticulture. Melatonin, an indoleamine, mediates many physiological processes in plants. Herein, we examined whether exogenously applied melatonin could improve the resistance of wine grape seedlings grown from cuttings to polyethylene glycol-induced water-deficient stress. The application of 10% polyethylene glycol (PEG) markedly inhibited the growth of cuttings, caused oxidative stress and damage from H2 O2 and O2∙-, and reduced the potential efficiency of Photosystem II and the amount of chlorophyll. Application of melatonin partially alleviated the oxidative injury to cuttings, slowed the decline in the potential efficiency of Photosystem II, and limited the effects on leaf thickness, spongy tissue, and stoma size after application of PEG. Melatonin treatment also helped preserve the internal lamellar system of chloroplasts and alleviated the ultrastructural damage induced by drought stress. This ameliorating effect may be ascribed to the enhanced activity of antioxidant enzymes, increased levels of nonenzymatic antioxidants, and increased amount of osmoprotectants (free proline). We conclude that the application of melatonin to wine grapes is effective in reducing drought stress.

Phenolic profiles and antioxidant properties of young wines made from Yan73 (Vitis vinifera L.) and Cabernet Sauvignon (Vitis vinifera L.) grapes treated by 24-epibrassinolide.

The grape berries of two varieties, Yan73 (Vitis vinifera L.) and Cabernet Sauvignon (CS) (Vitis vinifera L.) were treated with 0.40 mg/L 24-epibrassinolide (EBR), 1.00 mg/L brassinazole (Brz), and deionized water (control), at the veraison period. The EBR treatment significantly increased total phenolic content (TPC), total tannin content (TTC) and total anthocyanin content (TAC) of Yan73 and CS wines, whereas Brz treatment decreased TPC, total flavonoid content (TFC), TAC in the two wines. Moreover, the content of most of the phenolic compounds identified by HPLC-DAD/ESI-MS in EBR-treated wines was significantly higher than that in control. The antioxidant capacities, which determined using DPPH, ABTS and HRSA methods, of the wines were increased by EBR treatment as well. There was a good correlation between the antioxidant capacity and phenolic content. The results demonstrated that EBR could enhance the phenolic compounds and antioxidant capacity of Yan73 and CS wines, but the effects may vary by different cultivars.

Microclimate diversity drives grape quality difference at high-altitude: Observation using PCA analysis and structural equation modeling (SEM).

With the increasing threat of global warming, the cultivation of wine grapes in high-altitude with cool-temperature climates has become a viable option. However, the precise mechanism of environmental factors regulating grape quality remains unclear. Therefore, principal component analysis (PCA) was utilized to evaluate the quality of wine grape (Cabernet Sauvignon) in six high-altitude wine regions (1987, 2076, 2181, 2300, 2430, 2540 m). Structural equation modeling (SEM) was applied for the first time to identify the environmental contribution to grape quality. The wine grape quality existed spatial variation in basic physical attributes (BP), basic chemical compositions (BC), phenolic compounds (PC) and individual phenols. The PCA models (variance > 85 %) well separate wine grapes from the six altitudes into three groups according to scores. The score of grapes at 2300 m was significantly high (3.83), and the grapes of 2540 m showed a significantly low score (1.46). Subsequently, the malic acid, total tannin, total phenol, titratable acid, total anthocyanin, and skin thickness were the main differing indexes. SEM model characterized the relational network of differing indexes and microclimatic factors, which showed that temperature and extreme air temperature had a greater direct effect on differing indexes than light, with great contributions from soil temperature (0.98**), day-night temperature difference (0.825*), and day air temperature (0.789**). Our findings provided a theoretical basis for grape cultivation management in high-altitude regions and demonstrated that the SEM model is a useful tool for exploring the relationship between climate and fruit quality.

VvERF117 positively regulates grape cold tolerance through direct regulation of the antioxidative gene BAS1.

Cold stress significantly threatens grape quality, yield, and geographical distribution. Although ethylene-responsive factors (ERFs) are recognized for their pivotal roles in cold stress, the regulatory mechanisms of many ERFs contributing to tolerance remain unclear. In this study, we identified the cold-responsive gene VvERF117 and elucidated its positive regulatory function in cold tolerance. VvERF117 exhibits transcriptional activity and localizes to the nucleus. VvERF117 overexpression improved cold tolerance in transgenic Arabidopsis, grape calli, and grape leaves, whereas VvERF117 silencing increased cold sensitivity in grape calli and leaves. Furthermore, VvERF117 overexpression remarkably upregulated the expression of several stress-related genes. Importantly, BAS1, encoding a 2-Cys peroxidase (POD), was confirmed as a direct target gene of VvERF117. Meanwhile, compared to the wild-type, POD activity and H2O2 content were remarkably increased and decreased in VvERF117-overexpressing grape calli and leaves, respectively. Conversely, VvERF117 silencing displayed the opposite trend in grape calli and leaves under cold stress. These findings indicate that VvERF117 plays a positive role in cold resistance by, at least in part, enhancing antioxidant capacity through regulating the POD-encoding gene VvBAS1, leading to effective mitigation of reactive oxygen species.

Telomere-to-telomere and gap-free genome assembly of a susceptible grapevine species (Thompson Seedless) to facilitate grape functional genomics.

Grapes are globally recognized as economically significant fruit trees. Among grape varieties, Thompson Seedless holds paramount influence for fresh consumption and for extensive applications in winemaking, drying, and juicing. This variety is one of the most efficient genotypes for grape genetic modification. However, the lack of a high-quality genome has impeded effective breeding efforts. Here, we present the high-quality reference genome of Thompson Seedless with all 19 chromosomes represented as 19 contiguous sequences (N50 = 27.1 Mb) with zero gaps and prediction of all telomeres and centromeres. Compared with the previous assembly (TSv1 version), the new assembly incorporates an additional 31.5 Mb of high-quality sequenced data with annotation of a total of 30 397 protein-coding genes. We also performed a meticulous analysis to identify nucleotide-binding leucine-rich repeat genes (NLRs) in Thompson Seedless and two wild grape varieties renowned for their disease resistance. Our analysis revealed a significant reduction in the number of two types of NLRs, TIR-NB-LRR (TNL) and CC-NB-LRR (CNL), in Thompson Seedless, which may have led to its sensitivity to many fungal diseases, such as powdery mildew, and an increase in the number of a third type, RPW8 (resistance to powdery mildew 8)-NB-LRR (RNL). Subsequently, transcriptome analysis showed significant enrichment of NLRs during powdery mildew infection, emphasizing the pivotal role of these elements in grapevine's defense against powdery mildew. The successful assembly of a high-quality Thompson Seedless reference genome significantly contributes to grape genomics research, providing insight into the importance of seedlessness, disease resistance, and color traits, and these data can be used to facilitate grape molecular breeding efforts.

Exogenously applied abscisic acid to Yan73 (V. vinifera) grapes enhances phenolic content and antioxidant capacity of its wine.

Yan73 is a 'teinturier' red wine variety cultivated in China and widely used in winemaking to strengthen red wine colour. The objective of this study was to evaluate the effect of exogenous abscisic acid (ABA) applied to the grapevine cluster on the antioxidant capacity and phenolic content of the wine made from Yan73. Two hundred mg/l ABA was applied on Yan73 grapevine cluster during veraison. As they mature, these ABA-treated and untreated grape berries were transformed into wines, respectively, and the phenolic content and antioxidant capacity of these wines were compared. The results showed that phenolic content (total phenolics, tannins, flavonoids and anthocyanins) and antioxidant capacity were higher in the wine produced with ABA-treated Yan73 grapes than those in the wine from untreated grapes. Compared to Cabernet Sauvignon wine, Yan73 wine had higher phenolic content and stronger antioxidant capacity. These strongly suggest that exogenously applied ABA to Yan73 grapes can enhance phenolic content and antioxidant capacity of its wine, and Yan73 wine has the higher utilization value and potential for development.

Effects of ultraviolet and infrared radiation absence or presence on the aroma volatile compounds in winegrape during veraison.

Light environmental factors have been identified to influence grape aromas greatly. Among them, the effect of non-visible light on grape aroma compounds has scarcely been investigated during grape growth and development. In the present study, ultraviolet (UV) or infrared (IR) radiation was eliminated in the grape bunch zone, and the grape bunches were irradiated with UV or IR light in vitro. The effect of UV and IR radiation on the grape aroma profile of the Cabernet Sauvignon variety was assessed by headspace solid phase microextraction gas chromatography mass spectrometer (HS-SPME GC-MS). A total of 16 aroma compounds were identified in the grape berries under UV radiation absence (UV-) or IR radiation absence (IR-). They were classified into aliphatic alcohols, aliphatic acids, benzenolds, aldehydes, and monoterpenes. A total of 23 aroma compounds were identified in the grape berries under UV radiation presence (UV+) or IR radiation presence (IR+), which were classified into aliphatic alcohols, aliphatic ketones, aliphatic esters, aliphatic acids, monoterpenes, aldehydes, volatile phenols, and other volatiles. Linalool and hexanal aroma compounds were the most responsive to UV- and UV+, according to OPLS-DA analysis. Hexanal was increased by UV- and decreased by UV+, thus was negatively correlated with UV radiation. Benzaldehyde and 2-decanone were also found as the main differing aroma compounds according to VIP scores in the IR- and IR+, respectively. The significant differences of aroma compounds in three UV and IR intensities were also observed by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS). The content of acetic acid, 2-methylbutanal, and pentanal were reduced with the radiation intensity increase, and the content of 2-3-butanedione, butyl acetate, and 1-hexanol was enhanced, especially with UV radiation. This study improves our understanding of the non-visible light role in volatile aroma compound accumulation and further expands on the useful wavelength for plant growth and development. Our study provides a theoretical basis for non-visible light field management and indoor plant growth applications.

Effects of UVA disappearance and presence on the acylated anthocyanins formation in grape berries.

Ultraviolet A (UVA), the major component of the UV, plays a crucial role in formatting the characteristics of color in wine grapes by influencing its anthocyanin composition and contents. Results showed that anthocyanin biosynthesis was suppressed by UVA screening and enhanced by irradiation. The acetylation and p-coumaroylation of anthocyanins were more pronounced and showed positive correlation with a* and negative correlation with L*, b*, C*, and h, thereby leading to changes in color. Weighted gene co-expression network analysis showed that two modules (red and turquoise) were significantly related to the acetylation and p-coumaroylation of peonidin. In addition, relative gene expression assays and correlation analysis also indicated that VvMYBA1 might influence anthocyanin accumulation by directly regulating VvOMT expression and increasing the flux to the vacuole through VvGST4. In conclusion, the results helped in improving our understanding of the role of UVA in skin color formation.

Involvement of Anthocyanin Biosynthesis of Cabernet Sauvignon Grape Skins in Response to Field Screening and In Vitro Culture Irradiating Infrared Radiation.

To study the role of infrared (IR) radiation in the color change of the grape berry, field screening (IR-) and in vitro culture irradiation (IR+) were used. Acylated anthocyanin biosyntheses, including the biosynthesis of malvidin 3-O-glucoside, peonidin 3-O-glucoside, and their derivatives (acetylation and p-coumaroylation), were inhibited by IR-. IR+ promoted the biosynthesis of malvidin 3-O-glucoside and its derivatives, and IR+ inhibited the biosynthesis of peonidin 3-O-glucoside and its derivatives. WGCNA analysis revealed that the red module positively correlated with the flavonoid pathway. The hub genes were related to the anthocyanin pathway, including VvF3'5'H, VvANS, VvOMT1, VIT_18s0001g09400, and VvGST4. Further, the results revealed that transcription factors like RLK-Pelle, MYB, and C2H2 families were involved in response to IR radiation. Therefore, these results provide a complete understanding of IR radiation in grape skin color formation and the prospect of using supplemental light to improve the overall color of berries.

Characterization of 24-epibrassinolide-mediated modulation of the drought stress responses: Morphophysiology, antioxidant metabolism and hormones in grapevine (Vitis vinifera L.).

Drought stress is one of the major abiotic stresses that limit grape growth and yield. Brassinosteroids (BRs) are a class of phytohormones essential for plant growth, development, and adaptation to environmental stress. This study aimed to reveal the physiological and biochemical mechanisms of exogenous BRs in alleviating the drought stress in grapevines. Two-year-old grape seedlings (Vitis vinifera L.) were sprayed with 24-epibrassinolide (EBR), a synthetic analog of BRs, and then subjected to drought treatment. The results showed that exogenous EBR significantly mitigated the reduction of photosynthetic pigment contents and photosystem II efficiency and decreased the damage to chloroplasts when grape seedlings were subjected to drought stress. Drought stress resulted in the accumulation of reactive oxidative species (ROS) and an increase in lipid peroxidation. A reduction in oxidative damage was observed in EBR-pretreated plants, which was probably due to the elevated antioxidant system. Exogenous EBR improved the activities of superoxide dismutase (14%), catalase (18%), peroxidase (17%), and ascorbate peroxidase (9%), and promoted the accumulation of ascorbic acid (10%) and glutathione (7%) under drought stress. EBR pretreatment also promoted autophagic activity, which contributed to the degradation of damaged chloroplasts. Moreover, EBR pretreatment increased the concentrations of abscisic acid, jasmonic acid, auxin, and gibberellic acid. Taken together, exogenous EBR could ameliorate the deleterious effects of drought stress by up-regulating photosynthetic capacity, antioxidant system, autophagic activity, and hormone concentrations.

The Expression of Aroma Components and Related Genes in Merlot and Marselan Scion-Rootstock Grape and Wine.

Rootstocks were bred and selected from several species in order to enhance the resistance against biotic or abiotic stresses. There are few studies on the effect of rootstocks on aroma and related gene expression. This study focused on the effects of three rootstocks, Kober 5BB (5BB), 1103 Paulsen (1103P), and Selection Oppenheim (SO4), on the aroma and volatile-related gene expression levels of Merlot and Marselan berries and wines. These three rootstocks reduced the total aroma content of Merlot wine. 5BB upregulated VvLoXA and showed increased C6 alcohols. 1103P enhanced the linalool from Merlot berry, with marked upregulation of VvLinNer1. Conversely, rootstocks increased the total aroma content of Marselan berry, verified by the related expression levels of volatile-related genes. For Marselan berry, 5BB and 1103P upregulated five VvGTs and nine genes from the LOX and MEP pathway. 1103P increased the contents of C6 alcohols, C6 aldehydes, and citronellol from Marselan berry. Compared to 5BB and SO4, rootstock 1103P provided berries of better quality and richer aroma volatiles to Merlot and Marselan, while all three of the rootstocks had a significant effect on scion-rootstocks.

Effects of leaf removal on hexose accumulation and the expression of sugar unloading-related genes in syrah grapes.

Leaf removal (LR) around the cluster zone is a common practice for regulating grape quality. The purpose of this study was to assess the effects of cluster-zone leaf removal, applied at the pea-size stage of berry development, on berry soluble sugar, organic acid and phenolic compound, sugar unloading-related gene expression of Vitis. vinifera L. Syrah. Four different severities of leaf removal were applied: no leaf removal (Control), removing 2 leaves above the cluster (LR1), removing 4 leaves above the cluster (LR2), and removing 6 leaves above the cluster (LR3). The three leaf removal treatments (LR), especially removing 4 leaves (LR2), resulted in significantly higher reducing sugar, soluble sugar (glucose, fructose and sucrose), total anthocyanin and citric acid contents as compared to the control group during ripening for both vintages. At harvest, the LR treatments increased the transcript abundance of most sugar unloading-related genes. In addition, VvHT3, VvHT5, VvSUC11, VvSUC12, VvSS and VvcwINV were positively correlated with both reducing sugar contents and soluble sugar contents. Our results suggest that removing 4 leaves above the cluster is useful for improving the quality of Syrah (Vitis vinifera L.) grapes in cool climate regions with excessive leaves. These findings provide insights into the molecular basis of the relationship between leaf removing and hexose (glucose and fructose) accumulation in the grape berries.