Exogenous Abscisic Acid Mediates Berry Quality Improvement by Altered Endogenous Plant Hormones Level in "Ruiduhongyu" Grapevine

Quantitative Proteomics Analysis of ABA- and GA3-Treated Malbec Berries Reveals Insights into H2O2 Scavenging and Anthocyanin Dynamics

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remain unclear. We investigated the impact of ABA and GA3 application on Malbec grapevine berries across three developmental stages. We found similar patterns of berry total anthocyanin accumulation induced by both treatments, closely associated with berry H2O2 levels. Quantitative proteomics from berry skins revealed that ABA and GA3 positively modulated antioxidant defense proteins, mitigating H2O2. Consequently, proteins involved in phenylpropanoid biosynthesis were downregulated, leading to decreased anthocyanin content at the almost ripe stage, particularly petunidin-3-G and peonidin-3-G. Additionally, we noted increased levels of the non-anthocyanins E-viniferin and quercetin in the treated berries, which may enhance H2O2 scavenging at the almost ripe stage. Using a linear mixed-effects model, we found statistical significance for fixed effects including the berry H2O2 and sugar contents, demonstrating their roles in anthocyanin accumulation. In conclusion, our findings suggest a common molecular mechanism by which ABA and GA3 influence berry H2O2 content, ultimately impacting anthocyanin dynamics during ripening.

Enhancing Sugarcane Seedling Resilience to Water Stress through Exogenous Abscisic Acid: A Study on Antioxidant Enzymes and Phytohormone Dynamics

Exogenous hormones play a crucial role in regulating plant growth, development, and stress tolerance. However, the effects of exogenous abscisic acid (ABA) on sugarcane seedlings under water stress remain poorly understood. Here, in this study, a pot experiment was conducted on sugarcane seedlings 4 weeks after transplanting, employing three treatments: control (normal growth), drought (water stress), and drought + ABA (foliar application of 100 μM ABA before water stress). The main objectives of this research are to understand the effects of exogenous ABA on sugarcane seedlings under water stress conditions and to assess the changes in antioxidant enzyme activity and phytohormone levels in response to exogenous ABA. Water stress was induced in the solution culture by adding 25% (w/v) polyethylene glycol (PEG) 6000 to the Hoagland solution. Leaf samples were collected at 3, 6, and 9 days after treatment, and the photosynthetic and biochemical responses of ABA-treated plants to drought stress were investigated. The indole acetic acid (IAA) activity of the ABA-treated drought plants is compared to that of drought plants. Moreover, the endogenous ABA levels of the ABA-treated drought plants were significantly enhanced by 42.2, 39.9, and 42.3% at 3, 6, and 9 days, respectively, compared to those of drought plants. Additionally, the proline content of the ABA-treated drought plants significantly increased by 45 and 80% at 6 and 9 days, respectively, compared to that of drought plants. The expression of the catalase 1 (CAT1) gene was increased in the ABA-treated drought plants by 2.1-fold, 0.7-fold, and 1.37-fold at 3, 6, and 9 days, respectively, compared to that in drought plants. Similarly, the expression of superoxide dismutase, peroxidase, and ascorbate peroxidase genes of the ABA-treated drought plants also increased compared to those of the drought plants. In conclusion, foliar application of ABA mitigated the negative effects of water shortage of sugarcane plants under water stress. Applying ABA improved the antioxidant defense system of sugarcane plants under drought stress, thereby enhancing their photosynthetic activities and productivity.

Using In Vitro Cultured Berries to Unravel the Effects of Heat- and ABA-Induced Stress on Thiol Precursor Biosynthesis in Sauvignon Blanc

Global warming, heat waves, and seasonal drought pose serious threats to crops, such as grapevine, that are valued for their secondary metabolites, which are of primary importance for the wine industry. Discriminating the effects of distinct environmental factors in the open field is challenging. In the present study, in vitro cultured berries of Sauvignon Blanc were exposed to individual and combined stress factors to investigate the effects on the biosynthesis of the thiol precursors. Our results confirm the complexity and extreme reactivity of the accumulation process in grapes. However, they also indicate that heat stress has a positive effect on the production of the Cys-3SH precursor. Moreover, we identified several candidate genes, such as VvGSTs and VvGGT that are potentially involved in biosynthesis and consistently modulated. Nonetheless, we were unable to conclusively determine the effects of stresses on the biosynthesis of other precursors nor could we formulate hypotheses regarding their regulation.

Prohexadione-calcium improves grape quality by regulating endogenous hormones, sugar and acid metabolism and related enzyme activities in grape berries

Prohexadione-Calcium (Pro-Ca) plays key roles in improving fruit quality and yield by regulating various aspects of plant growth. However, the effects of how Pro-Ca regulates the regulation of sugar and acid balance and its impact on the production of volatile aroma substances during fruit growth and development are poorly understood. In this study, the Pro-Ca solutions developed at concentrations of 200, 400, 600 and 800 mg·L-1 were sprayed on the entire "Chardonnay" grape tree 22, 42, 62 and 82 days after initial flowering. The values of endogenous hormones, sugar and acid content, enzyme activities and flavor content were then measured in grapes 45, 65, 85 and 105 days (ripeness stage) after the initial flowering. The results showed that Pro-Ca had significant effects on fruits during development, including reducing ABA content, increasing ZT, GA3 and IAA levels, promoting fruit ripening and enhancing enzymes, which are involved in sugar and acid synthesis. Consequently, these effects led to an increase in sugar and acid content in the berries. Particularly during the ripening phase, the application of 600 mg L-1 Pro-Ca resulted in an increase in soluble sugar content of 11.28% and a significant increase in citric acid and malic acid content of 97.80% and 68.86%, respectively. Additionally, Pro-Ca treatment enhanced both the variety and quantity of aroma compounds present in the berries, with the 600 mg·L-1 Pro-Ca treatment showcasing the most favorable impact on volatile aroma compounds in 'Chardonnay' grapes. The levels of aldehydes, esters, alcohols, phenols, acids, ketones, and terpenes were significantly higher under the 600 mg·L-1 Pro-Ca treatment compared to those of control with 51.46 - 423.85% increase. In conclusion, Pro-Ca can regulate the content of endogenous hormones and the activities of enzymes related to sugar and acid metabolism in fruit, thereby increasing the content of soluble sugar and organic acid in fruit and the diversity and concentration of fruit aroma substances. Among them, foliar spraying 600 mg · L-1 Pro-Ca has the best effect. In the future, we need to further understand the molecular mechanism of Pro-Ca in grape fruit to lay a solid foundation for quality improvement breeding.

Improving berry quality and antioxidant ability in 'Ruidu Hongyu' grapevine through preharvest exogenous 2,4-epibrassinolide, jasmonic acid and their signaling inhibitors by regulating endogenous phytohormones

Grape berries contain a variety of metabolites, such as anthocyanins, sugars, fatty acids, and antioxidants. Endogenous phytohormones strongly influence these metabolites, which regulate berry quality improvement. In this study, we evaluated the effects of 2,4-epibrassinolide (EBR, brassinolide (BR)-like growth regulator), jasmonic acid (JA), and their signaling inhibitors brassinazole (Brz), and sodium diethyldithiocarbamate (DIECA) on berry quality and antioxidant ability. Overall, the pre-harvest application of 0.5 mg L^-1 EBR and 100 μmol L^-1 JA significantly influences the quality of the grape berry. Results showed that EBR was superior to other treatments at enhancing the content of different metabolites, including anthocyanins, fructose, glucose, and a variety of fatty acids, in grapes. EBR and JA also enhanced the synthesis of gibberellin₃ (GA₃), cytokinin (CTK), salicylic acid (SA), JA, methyl jasmonate (MeJA), BR, and abscisic acid (ABA), while inhibiting the synthesis of auxin (IAA). Most genes related to BR/JA and anthocyanins/sugars/fatty acids biosynthesis were up-regulated. The effects of Brz and DIECA on the grape berry quality were totally reversed throughout the study, as shown by EBR and JA. According to correlation analysis, EBR and JA have a beneficial positive interaction that promotes the formation of strong coherences in grape berries between ABA/IAA/ZT-fruit expansion, BR/JA/MeJA/GA₃/ZR-biochemical characteristics development, JA/MeJA/ABA/GA₃/SA/ZR-antioxidant capacity enhancement, and JA/MeJA/IAA/GA₃/ZT/ZR-fatty acids accumulation. In this regard, we concluded that preharvest exogenous 0.5 mg L^-1 EBR and 100 μmol L^-1 JA is a successful way to improve grape berry quality.

Transcriptome analysis revealed the expression levels of genes related to abscisic acid and auxin biosynthesis in grapevine (Vitis vinifera L.) under root restriction

The root system is essential for the stable growth of plants. Roots help anchor plants in the soil and play a crucial role in water uptake, mineral nutrient absorption and endogenous phytohormone formation. Root-restriction (RR) cultivation, a powerful technique, confines plant roots to a specific soil space. In the present study, roots of one-year-old "Muscat Hamburg" grapevine under RR and control (nR) treatments harvested at 70 and 125 days after planting were used for transcriptome sequencing, and in total, 2031 (nR7 vs. nR12), 1445 (RR7 vs. RR12), 1532 (nR7 vs. RR7), and 2799 (nR12 vs. RR12) differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment analysis demonstrated that there were several genes involved in the response to different phytohormones, including abscisic acid (ABA), auxin (IAA), ethylene (ETH), gibberellins (GAs), and cytokinins (CTKs). Among them, multiple genes, such as PIN2 and ERF113, are involved in regulating vital plant movements by various phytohormone pathways. Moreover, following RR cultivation, DEGs were enriched in the biological processes of plant-type secondary cell wall biosynthesis, the defense response, programmed cell death involved in cell development, and the oxalate metabolic process. Furthermore, through a combined analysis of the transcriptome and previously published microRNA (miRNA) sequencing results, we found that multiple differentially expressed miRNAs (DEMs) and DEG combinations in different comparison groups exhibited opposite trends, indicating that the expression levels of miRNAs and their target genes were negatively correlated. Furthermore, RR treatment indeed significantly increased the ABA content at 125 days after planting and significantly decreased the IAA content at 70 days after planting. Under RR cultivation, most ABA biosynthesis-related genes were upregulated, while most IAA biosynthesis-related genes were downregulated. These findings lay a solid foundation for further establishing the network through which miRNAs regulate grapevine root development through target genes and for further exploring the molecular mechanism through which endogenous ABA and IAA regulate root architecture development in grapevine.