Cytokinin but not gibberellin application had major impact on the phenylpropanoid pathway in grape

Integrated Transcriptomic and Proteomic Analysis Identifies Novel Regulatory Genes Associated with Plant Growth Regulator-Induced Astringency in Grape Berries

Astringency influences the sensory characteristics and flavor quality of table grapes. We tested the astringency sensory attributes of berries and investigated the concentration of flavan-3-ols/proanthocyanidins (PAs) in skins after the application of the plant growth regulators CPPU and GA3 to the flowers and young berries of the "Summer Black" grape. Our results showed that CPPU and GA3 applications increase sensory astringency perception scores and flavan-3-ol/proanthocyanidin concentrations. Using integrated transcriptomic and proteomic analysis, differentially expressed transcripts and proteins associated with growth regulator treatment were identified, including those for flavonoid biosynthesis that contribute to the changes in sensory astringency levels. Transient overexpression of candidate astringency-related regulatory genes in grape leaves revealed that VvWRKY71, in combination with VvMYBPA1 and VvMYC1, could promote the biosynthesis of proanthocyanidins, while overexpression of VvNAC83 reduced the accumulation of proanthocyanidins. However, in transient promoter studies in Nicotiana benthamiana, VvWRKY71 repressed the promoter of VvMYBPA2, while VvNAC83 had no significant effect on the promoter activity of four PA-related genes, and VvMYBPA1 was shown to activate its own promoter. This study provides new insights into the molecular mechanisms of sensory astringency formation induced by plant growth regulators in grape berries.

Cytokinin promotes anthocyanin biosynthesis via regulating sugar accumulation and MYB113 expression in Eucalyptus

Anthocyanins are flavonoid-like substances that play important roles in plants' adaptation to various environmental stresses. In this research, we discovered that cytokinin (CK) alone could effectively induce the anthocyanin biosynthesis in Eucalyptus and many other perennial woody plant species, but not in tobacco and Arabidopsis, suggesting a diverse role of CK in regulating anthocyanin biosynthesis in different species. Transcriptomic and metabolomic strategies were used to further clarify the specific role of CK in regulating anthocyanin biosynthesis in Eucalyptus. The results showed that 801 and 2241 genes were differentially regulated at 6 and 24 h, respectively, after CK treatment. Pathway analysis showed that most of the differentially expressed genes were categorized into pathways related to cellular metabolism or transport of metabolites, including amino acids and sugars. The metabolomic results well supported the transcriptome data, which showed that most of the differentially regulated metabolites were related to the metabolism of sugar, amino acids and flavonoids. Moreover, CK treatment significantly induced the accumulation of sucrose in the CK-treated leaves, while sugar starvation mimicked by either defoliation or shading treatment of the basal leaves significantly reduced the sugar increase of the CK-treated leaves and thus inhibited CK-induced anthocyanin biosynthesis. The results of in vitro experiment also suggested that CK-induced anthocyanin in Eucalyptus was sugar-dependent. Furthermore, we identified an early CK-responsive transcription factor MYB113 in Eucalyptus, the expression of which was significantly upregulated by CK treatment in Eucalyptus, but was inhibited in Arabidopsis. Importantly, the overexpression of EgrMYB113 in the Eucalyptus hairy roots was associated with significant anthocyanin accumulation and upregulation of most of the anthocyanin biosynthetic genes. In conclusion, our study demonstrates a key role of CK in the regulation of anthocyanin biosynthesis in Eucalyptus, providing a molecular basis for further understanding the regulatory mechanism and diversity of hormone-regulated anthocyanin biosynthesis in different plant species.

Modification of Gene Expression of Tomato Plants through Foliar Flavonoid Application in Relation to Enhanced Growth

The exogenous application of phenolic compounds is increasingly recognized as a valuable strategy for promoting growth and mitigating the adverse effects of abiotic stress. However, the biostimulant effect under optimal conditions has not been thoroughly explored. In this study, we investigated the impact of foliar application of flavonoids, specifically CropBioLife (CBL), on tomato plants grown under controlled conditions. Our study focused on determining growth parameters, such as cell size, and assessing the concentration of hormones. Principal component analysis (PCA) from all physiological variables was determined. Additionally, we utilized high-throughput mRNA-sequencing technology and bioinformatic methodologies to robustly analyze the transcriptomes of tomato leaves regulated by flavonoids. The findings revealed that CBL primarily influenced cell enlargement by 60%, leading to increased growth. Furthermore, CBL-treated plants exhibited higher concentrations of the hormone zeatin, but lower concentrations of IAA (changes of 50%). Moreover, RNA-seq analysis indicated that CBL-treated plants required increased mineral transport and water uptake, as evidenced by gene expression patterns. Genes related to pathways such as fatty acid degradation, phenylpropanoid biosynthesis, and ABC transporters showed regulatory mechanisms governing internal flavonoid biosynthesis, transport, and tissue concentration, ultimately resulting in higher flavonoid concentrations in tomato leaves.

Aroma profiling of Shine Muscat grape provides detailed insights into the regulatory effect of gibberellic acid and N-(2-chloro-4-pyridinyl)-N-phenylurea applications on aroma quality

As plant growth regulators, gibberellic acid (GA₃) and CPPU [forchlorfenuron, N-(2-chloro-4-pyridinyl)-N-phenylurea] are widely used in the production of table grapes. However, how these compounds regulate the aroma quality remains unclear. By measuring free and bound aroma compounds in Shine Muscat grapes from eight groups during whole growth period, GA₃ and CPPU were both found to significantly promote the synthesis of acyclic monoterpenes and (E)-2-hexenal, and double applications were found to further increase the aroma compound contents. On the other hand, GA₃ and CPPU obviously promoted the expansion of berries, and the effect of promoting the synthesis of aroma compounds was largely diminished. In conclusion, free compound concentrations in berry were almost unaffected by GA₃ and CPPU. From the perspective of aroma compounds, a highly concerted interplay was observed for terpenes, and bound compounds exhibited higher correlations than those of free compounds. In addition, 17 compounds could be used as markers that indicated the developmental timing of berries.

Comparative Transcriptomics of Multi-Stress Responses in Pachycladon cheesemanii and Arabidopsis thaliana

The environment is seldom optimal for plant growth and changes in abiotic and biotic signals, including temperature, water availability, radiation and pests, induce plant responses to optimise survival. The New Zealand native plant species and close relative to Arabidopsis thaliana, Pachycladon cheesemanii, grows under environmental conditions that are unsustainable for many plant species. Here, we compare the responses of both species to different stressors (low temperature, salt and UV-B radiation) to help understand how P. cheesemanii can grow in such harsh environments. The stress transcriptomes were determined and comparative transcriptome and network analyses discovered similar and unique responses within species, and between the two plant species. A number of widely studied plant stress processes were highly conserved in A. thaliana and P. cheesemanii. However, in response to cold stress, Gene Ontology terms related to glycosinolate metabolism were only enriched in P. cheesemanii. Salt stress was associated with alteration of the cuticle and proline biosynthesis in A. thaliana and P. cheesemanii, respectively. Anthocyanin production may be a more important strategy to contribute to the UV-B radiation tolerance in P. cheesemanii. These results allowed us to define broad stress response pathways in A. thaliana and P. cheesemanii and suggested that regulation of glycosinolate, proline and anthocyanin metabolism are strategies that help mitigate environmental stress.

Proteomic and metabolomic integration reveals the effects of pre-flowering cytokinin applications on central carbon metabolism in table grape berries

Consumers around the world prefer high quality table grapes. To achieve higher quality traits at ripening, grapevine producers apply different plant growth regulators. The synthetic cytokinin forchlorfenuron N-(2-chloro-4-pyridinyl)-N'-phenylurea (CPPU) is widely used, its effect on grape quality is poorly understood. We hypothesized that the use of CPPU in pre-flowering can lead to changes in the metabolism that affects grape quality at harvest. Therefore, we investigated the role of CPPU applications on the quality of grapes by integrating proteomics and metabolomics. CPPU-treated grapevines showed a significant increase in berry size and firmness. Proteomic analyses indicated that CPPU-treated berries accumulated enzymes associated with carbohydrate metabolism, glycolysis, and tricarboxylic acid (TCA) cycle at harvest. Metabolomic analyses showed shifts in the abundance of compounds associated with carbohydrate metabolism and TCA cycle in CPPU-treated grapes. These findings suggest that CPPU applications modulate central carbon metabolism, improving grape berry quality.

The Potential Use of Plant Growth Regulators for Modification of the Industrially Valuable Volatile Compounds Synthesis in Hylocreus undatus Stems

The pitaya (dragon fruit) Hylocereus is a genus which belongs to the Cactaceae family. It is native to Mexico, occurring also in other regions of Central and South America. Pitaya fruit is mainly intended for consumption and for this reason the species is grown commercially. The fruit is a rich source of vitamins, biologically active compounds, and dietary fibre. Using in vitro culture can accelerate the process of reproduction and growth of pitaya plants. Profiling of volatile compounds contained in the stem of Hylocereus undatus was carried out using the SPME-GC-MS technique. The main compounds present were hexanal, 2-hexenal and 1-hexanol. The results showed differences in the occurrence of volatile compounds between plants grown in media with an addition of BA (6-benzylaminopurine) and IAA (indole-3-acetic acid), which have been used as plant growth regulators. Statistically significant differences between the contents of volatile compounds were observed in the case of 2-hexenal and 1-hexanol. The effect of BA on reducing the amount of volatile compounds was observed. However, introduction of IAA to the in vitro medium resulted in more compounds being synthesized. This study is the first to describe the volatile compounds in the pitaya stem. The results indicate that plant hormones are able to modify the profile of volatile compounds.

Identification and expression analysis of invertase family genes during grape (Vitis vinifera L.) berry development under CPPU and GA treatment

Sugar is crucial for grape berry, whether used for fresh food or wine. However, berry enlargement treatment with forchlorfenuron (N-(2-chloro4-pyridyl)-N'-phenylurea) (CPPU, a synthetic cytokinin) and gibberellin (GA) always had adverse effects on sugar accumulation in some grape varieties, especially CPPU. Therefore exploring the molecular mechanisms behind these adverse effects could provide a foundation for improving or developing technology to mitigate the effects of CPPU/GA treatments for grape growers. In the present study, invertase (INV) family, the key gene controlling sugar accumulation, was identified and characterized on the latest annotated grape genome. Their express pattern, as well as invertase activity and sugar content, were analyzed during grape berry development under CPPU and GA₃ treatment to explore the potential role of INV members under berry enlargement treatment in grapes. Eighteen INV genes were identified and divided into two sub-families: 10 neutral INV genes (Vv-A/N-INV1-10) and 8 acid INV genes containing 5 CWINV (VvCWINV1-5) and 3 VIN (VvVIN1-3). At the early development stage, both CPPU and GA₃ treatment decreased the hexose level in berries of 'Pinot Noir' grape, whereas the activity of three types inverstase (soluble acid INV, insoluble acid INV, and neutral INV) increased. Correspondingly, most of INV members were up-regulated by GA₃ /CPPU application at least one sampling time point during early berry development, including VvCWINV1, 2, 3, 4, 5, VvVIN1, 2, 3 and Vv-A/N-INV1, 2, 5, 6, 7, 8, 10. At maturity, the sugar content in CPPU-treated berries is still lower than that in the control. Soluble acid INV and neutral INV, rather than insoluble acid INV, presented lower activity in CPPU-treated berries. Meanwhile, several corresponding genes, such as VvVIN2 and Vv-A/N-INV2, 8, 10 in ripening berries were obviously down-regulated by CPPU treatment. These results suggested that most of INV members could be triggered by berry enlargement treatment during early berry development, whereas VvVINs and Vv-A/N-INVs, but not VvCWINVs, could be the limiting factor resulting in decreased sugar accumulation in CPPU-treated berries at maturity. In conclusion, this study identified the INV family on the latest annotated grape genome and selected several potential members involving in the limit of CPPU on final sugar accumulation in grape berry. These results provide candidate genes for further study of the molecular regulation of CPPU and GA on sugar accumulation in grape.

In Vitro Cultures of Scutellaria brevibracteata subsp. subvelutina as a Source of Bioactive Phenolic Metabolites

Some of the more than 350 Scutellaria species, such as S. baicalensis and S. lateriflora, have been used in traditional medicine and today play an important role in official phytotherapy. Other species have been less investigated, and their therapeutic potential is unknown. This is one of the few studies on Scutellaria brevibracteata subsp. subvelutina, and the first research of this species' in vitro cultures. The aim of this study was to establish an in vitro culture and analyse its phytochemical profile and biological activity. In the methanolic extracts from biomass cultured on six solid Murashige and Skoog (MS) medium variants supplemented with different combinations of 6-benzylaminopurine (BAP) and 1-naphthaleneacetic acid (NAA) in the range 0.5-3 mg/L analysed by HPLC, the presence of specific flavonoids (baicalein, baicalin, wogonin, wogonoside, scutellarin, chrysin), phenylpropanoid glycosides (verbascoside, isoverbascoside), and phenolic acids (p-hydroxybenzoic, caffeic, ferulic, m-coumaric acids) was confirmed. The dominant metabolites were wogonoside and verbascoside with the highest content of 346 and 457 mg/100 g DW, respectively. Thus, the extract with the highest content of bioactive metabolites was selected for further research and subjected to evaluation of antioxidant and antimicrobial potential. The extract exhibited good free radical scavenging activity (IC₅₀ = 0.92 ± 0.01 mg/mL) and moderate reducing power and chelating activity. The brine shrimp lethality bioassay proved its lack of biotoxicity. Antimicrobial activity was tested against sixteen strains of Gram-positive and Gram-negative bacteria and fungi. The strongest growth inhibitory activity was observed against Trichophyton tonsurans.

Modification of wine phenolic profiles by gibberellic acid application in 'Cabernet Gernischt' grapevines before anthesis

BACKGROUND

Vitis vinifera L. 'Cabernet Gernischt' grapes from the Yantai wine region of China usually form dense clusters and contain low phenolic content. We applied five concentrations (ranged from 5 to 25 mg L^-1 ) of gibberellic acid (GA₃ ) to 'Cabernet Gernischt' before anthesis to decrease cluster compactness in two consecutive vintages. Yield indices, grape maturity, and wine phenolic compounds were determined.

RESULTS

GA₃ application significantly reduced cluster compactness, bunch weight, and yield per vine, but it did not significantly improve fruit ripening. The levels of total phenolics, total tannins, and total anthocyanins in wine were enhanced by GA₃ application, with 10 and 15 mg L^-1 GA₃ treatments consistently producing a significant increase in the concentrations of mavidin, cyanidin, and their derivatives. Specifically, trans-resveratrol was consistently significantly increased by 15 mg L^-1 GA₃ application. Principal component analysis of phenolic compounds demonstrated the differences among wines produced from GA₃ treatment groups and the control.

CONCLUSION

Overall, wine phenolic profiles could be significantly modified by application of low concentrations of GA₃ before anthesis. Application of high levels of GA₃ is not recommended due to significant yield decrease. © 2022 Society of Chemical Industry.

Key metabolites and mechanistic insights in forchlorfenuron controlling kiwifruit development

Forchlorfenuron (CPPU) is a plant growth regulator widely applied on kiwifruit to improve yield, however, there are rarely reports on its effects on the nutrients of kiwifruits. Based on UHPLC-Q-TOF-MS, the effects of CPPU on metabolism profile and nutrient substances of two kiwifruit varieties during development were investigated by non-targeted metabolomics. A total of 115 metabolites were identified, and 29 differential metabolites were confirmed and quantified using certified reference standards. Metabolic profile indicated that CPPU promoted kiwifruit development during the main expansion stages at the molecular level, and the effects varied slightly for different varieties. In the early and middle stages of kiwifruit development, the anthocyanin, flavone and flavonol biosynthesis were down-regulated in both varieties, and flavanols biosynthesis was down-regulated only in Hayward variety. Arginine biosynthesis was down-regulated at all stages till the harvest. Although the synthesis of these nutrient substances in kiwifruits was mostly down-regulated by CPPU, the negative effects became mild at harvest time, and positively, the significant increase of sucrose and decrease of organic acids at harvest time could help to improve the taste of kiwifruits.

Effects of the application of forchlorfenuron (CPPU) on the composition of verdejo grapes

The application of cytokinins such as forchlorfenuron (CPPU) has been widely used in table grape varieties to increase yield and berry size. However, the potential interest of these phytoregulators in wine grapes have been scarcely analyzed. The objective of this study has been to evaluate the influence of CPPU treatment on the agronomic performance and composition of Verdejo grapes. The trial was conducted in 2021, in the Protected Designation of Origin “Rueda” (Spain). CPPU was applied using a concentration of 15 mg/L, by spraying the bunches when the berries were 5-6 mm in diameter. The photosynthesis rates and the stem water potential, measured after the application, tended to decrease in the treated plants without modify the values ​​of vine yield and vigour. The treatment significantly affected the content of soluble solids and total polyphenols of the grape must, detecting increases of 15.4% and 7%, respectively, compared to the controls. Preliminary results suggest that the application of CPPU on the bunches could improve the quality of the Verdejo grapes. The treatment would be interesting to apply in cultivation conditions where the harvest has difficulties to reach an adequate level of maturity, such as excessive vigour or too cold climate.

Mechanism of [CO2] Enrichment Alleviated Drought Stress in the Roots of Cucumber Seedlings Revealed via Proteomic and Biochemical Analysis

Cucumber is one of the most widely cultivated greenhouse vegetables, and its quality and yield are threatened by drought stress. Studies have shown that carbon dioxide concentration ([CO₂]) enrichment can alleviate drought stress in cucumber seedlings; however the mechanism of this [CO₂] enrichment effect on root drought stress is not clear. In this study, the effects of different drought stresses (simulated with 0, 5% and 10% PEG 6000, i.e., no, moderate, and severe drought stress) and [CO₂] (400 μmol·mol^-1 and 800 ± 40 μmol·mol^-1) on the cucumber seedling root proteome were analyzed using the tandem mass tag (TMT) quantitative proteomics method. The results showed that after [CO₂] enrichment, 346 differentially accumulating proteins (DAPs) were found only under moderate drought stress, 27 DAPs only under severe drought stress, and 34 DAPs under both moderate and severe drought stress. [CO₂] enrichment promoted energy metabolism, amino acid metabolism, and secondary metabolism, induced the expression of proteins related to root cell wall and cytoskeleton metabolism, effectively maintained the balance of protein processing and degradation, and enhanced the cell wall regulation ability. However, the extent to which [CO₂] enrichment alleviated drought stress in cucumber seedling roots was limited under severe drought stress, which may be due to excessive damage to the seedlings.

Effects of gibberellins on important agronomic traits of horticultural plants

Horticultural plants such as vegetables, fruits, and ornamental plants are crucial to human life and socioeconomic development. Gibberellins (GAs), a class of diterpenoid compounds, control numerous developmental processes of plants. The roles of GAs in regulating growth and development of horticultural plants, and in regulating significant progress have been clarified. These findings have significant implications for promoting the quality and quantity of the products of horticultural plants. Here we review recent progress in determining the roles of GAs (including biosynthesis and signaling) in regulating plant stature, axillary meristem outgrowth, compound leaf development, flowering time, and parthenocarpy. These findings will provide a solid foundation for further improving the quality and quantity of horticultural plants products.

Infection by Moniliophthora perniciosa reprograms tomato Micro-Tom physiology, establishes a sink, and increases secondary cell wall synthesis

Witches' broom disease of cacao is caused by the pathogenic fungus Moniliophthora perniciosa. By using tomato (Solanum lycopersicum) cultivar Micro-Tom (MT) as a model system, we investigated the physiological and metabolic consequences of M. perniciosa infection to determine whether symptoms result from sink establishment during infection. Infection of MT by M. perniciosa caused reductions in root biomass and fruit yield, a decrease in leaf gas exchange, and down-regulation of photosynthesis-related genes. The total leaf area and water potential decreased, while ABA levels, water conductance/conductivity, and ABA-related gene expression increased. Genes related to sugar metabolism and those involved in secondary cell wall deposition were up-regulated upon infection, and the concentrations of sugars, fumarate, and amino acids increased. 14C-glucose was mobilized towards infected MT stems, but not in inoculated stems of the MT line overexpressing CYTOKININ OXIDASE-2 (35S::AtCKX2), suggesting a role for cytokinin in establishing a sugar sink. The up-regulation of genes involved in cell wall deposition and phenylpropanoid metabolism in infected MT, but not in 35S::AtCKX2 plants, suggests establishment of a cytokinin-mediated sink that promotes tissue overgrowth with an increase in lignin. Possibly, M. perniciosa could benefit from the accumulation of secondary cell walls during its saprotrophic phase of infection.

Phenylalanine ammonia lyase is more relevant than Chalcone synthase and Chalcone isomerase in the biosynthesis of flavonoids during postharvest senescence of broccoli

Broccoli contains a high content of nutraceutical compounds, such as glucosinolates and flavonoids. In this work, the effect of different treatments that modulate postharvest senescence of broccoli was evaluated and flavonoid metabolism during postharvest storage was analyzed at 20°C. A decrease in hue angle (HUE°) and chlorophylls and an increase in flavonoid content were detected during senescence. It observed that most of the treatments that delayed senescence also decreased flavonoid content, except visible light and UV-C treatments. In all cases, a direct correlation between those treatments that increased flavonoid biosynthesis and BoPAL gene expression was detected. This response was not detected in the expression of the other two flavonoid synthesis relevant genes BoCHS and BoCHI, suggesting that BoPAL has a greater influence on the regulation of the via, during broccoli senescence. PRACTICAL APPLICATIONS: Broccoli is a vegetable with valuable nutritional properties. Because it is in full development at the time of harvest, it has a short shelf life. In this work, it is showed that visible light and UV-C treatments not only delayed the senescence of broccoli, but also increased flavonoid content. Our results suggest that the most important enzyme in the phenylpropanoid biosynthesis pathway during broccoli postharvest is phenylalanine ammonia lyase, and that this may be a key point in regulating the biosynthesis of these nutritionally valuable compounds.

Extraction and Analysis of Phenolic Compounds from Grape Berries

Phenolics are ubiquitous compounds that represent the most abundant and diverse class of plant metabolites. From an analytical point of view, phenolics can be divided into soluble phenolics such as phenolic acids, phenylpropanoids, flavonoids and quinones, and nonsoluble compounds such as proanthocyanidins, lignins, and cell wall-bound hydroxycinnamic acids. Extraction of phenolics from the sample material is the first step toward their analysis. Biochemical methods for determination of total phenolics content were widely used in the past but modern chromatographic and mass spectrometric methods for identification and quantification of individual compounds are available in recent years. In this chapter, we describe methods for phenolic compounds extraction used in our laboratories from berries of Vitis vinifera and analytical methods including HPLC coupled to DAD detector and Q-TOF LC/MS for their analysis.

The Effect of Ethanol Treatment on the Quality of a New Table Grape Cultivar It 681-30 Stored at Low Temperature and after a 7-Day Shelf-Life Period at 20 °C: A Molecular Approach

Despite the fact that many studies have examined the effectiveness of different gaseous postharvest treatments applied at low temperature to maintain table grape quality, the use of ethanol vapor has hardly been investigated. Thus, this work has studied the effectiveness of ethanol vapor-generating sachets in the maintenance of It 681–30 table grape quality, a new cultivar, during storage at low temperature and after the shelf-life period at 20 °C. To this end, various quality assessments have been carried out and the effect of the ethanol treatment on the expression of different genes (phenylpropanoids, transcription factors, PRs, and aquaporins) was determined. The results indicated that the application of ethanol vapor reduced the total decay incidence, weight loss, and the rachis browning index in It 681–30 grapes stored at 0 °C and after the shelf-life period at 20 °C, as compared to non-treated samples. Moreover, the modulation of STS7 and the different PR genes analyzed seems to play a part in the molecular mechanisms activated to cope with fungal attacks during the postharvest of It 681–30 grapes, and particularly during the shelf-life period at 20 °C. Furthermore, the expression of aquaporin transcripts was activated in samples showing higher weight loss. Although further work is needed to elucidate the role of ethanol in table grape quality, the results obtained in this work provide new insight into the transcriptional regulation triggered by ethanol treatment.