Stilbene accumulation and expression of stilbene biosynthesis pathway genes in wild grapevine Vitis amurensis Rupr

Wild Vitis Species as Stilbenes Sources: Cane Extracts and Their Antibacterial Activity against Listeria monocytogenes

Grapevines (Vitis spp.) produce several valuable polyphenol-type secondary metabolites including various stilbenoids. Although the potential application of stilbenes may offer alternative solutions to food safety or health challenges, only little information is available on their antibacterial activity against foodborne pathogens. In this work, high-performance liquid chromatography was used to analyze the stilbenoid profile of various wild Vitis species, including V. amurensis, V. davidii, V. pentagona, and V. romanetii, selected from the gene bank for grapes at the University of Pécs, Hungary. We found that the stilbene profile of cane extracts is strongly genotype-dependent, showing the predominant presence of ε-viniferin with a wide concentration range ≈ 320-3870 µg/g dry weight. A novel yet simple and efficient extraction procedure was developed and applied for the first time on grape canes, resulting in ε-viniferin-rich crude extracts that were tested against Listeria monocytogenes, an important foodborne pathogen. After 24 h exposure, V. pentagona and V. amurensis crude extracts completely eliminated the bacteria at a minimum bactericidal concentration of 42.3 µg/mL and 39.2 µg/mL of ε-viniferin, respectively. On the other hand, V. romanetii extract with 7.8 µg/mL of ε-viniferin resulted in 4 log reduction in the viable bacterial cells, while V. davidii extract with 1.4 µg/mL of ε-viniferin did not show significant antibacterial activity. These findings indicate that the ε-viniferin content was directly responsible for the antibacterial effect of cane extract. However, pure ε-viniferin (purity > 95%) required a higher concentration (188 µg/mL) to eradicate the bacteria under the same conditions, suggesting the presence of other antibacterial compounds in the cane extracts. Investigating the onset time of the bactericidal action was conducted through a kinetic experiment, and results showed that the reduction in living bacterial number started after 2 h; however, the bactericidal action demanded 24 h of exposure. Our results revealed that the canes of V. pentagona and V. amurensis species are a crucial bio-source of an important stilbene with antimicrobial activity and health benefits.

The Effect of External Treatment of Arabidopsis thaliana with Plant-Derived Stilbene Compounds on Plant Resistance to Abiotic Stresses

Stilbenes are a group of plant phenolic secondary metabolites, with trans-resveratrol (3,5,4'-trihydroxy-trans-stilbene) being recognized as the most prominent and studied member. Stilbenes have a great potential for use in agriculture and medicine, as they have significant activities against plant pathogens and have valuable beneficial effects on human health. In this study, we analyzed the effects of direct application of stilbenes, stilbene precursor, and stilbene-rich extract solutions to the plant foliar surface for increasing the resistance of Arabidopsis thaliana to various abiotic stresses (heat, cold, drought, and soil salinity). Exogenous treatment of A. thaliana with stilbenes (trans-resveratrol, piceid, and spruce bark extract) and phenolic precursor (p-coumaric acid or CA) during germination resulted in considerable growth retardation of A. thaliana plants: a strong delay in the root and stem length of 1-week-old seedlings (in 1.3-4.5 fold) and rosette diameter of 1-month-old plants (in 1.2-1.8 fold), while the 2-month-old treated plants were not significantly different in size from the control. Plant treatments with stilbenes and CA increased the resistance of A. thaliana to heat and, to a lesser extent, to soil salinity (only t-resveratrol and spruce extract) to drought (only CA), while cold resistance was not affected. Plant treatments with stilbenes and CA resulted in a significant increase in plant resistance and survival rates under heat, with plants showing 1.5-2.3 times higher survival rates compared to untreated plants. Thus, exogenous stilbenes and a CA are able to improve plant survival under certain abiotic stresses via specific activation of the genes involved in the biosynthesis of auxins, gibberellins, abscisic acid, and some stress-related genes. The present work provides new insights into the application of stilbenes to improve plant stress tolerance.

The Effect of Stress Hormones, Ultraviolet C, and Stilbene Precursors on Expression of Calcineurin B-like Protein (CBL) and CBL-Interacting Protein Kinase (CIPK) Genes in Cell Cultures and Leaves of Vitis amurensis Rupr

Calcium serves as a crucial messenger in plant stress adaptation and developmental processes. Plants encode several multigene families of calcium sensor proteins with diverse functions in plant growth and stress responses. Several studies indicated that some calcium sensors may be involved in the regulation of secondary metabolite production in plant cells. The present study aimed to investigate expression of calcineurin B-like proteins (CBL) and CBL-interacting protein kinase (CIPK) in response to conditions inducting biosynthesis of stilbenes in grapevine. We investigated CBL and CIPK gene expression in wild-growing grapevine Vitis amurensis Rupr., known as a rich stilbene source, in response to the application of stilbene biosynthesis-inducing conditions, including application of stress hormones (salicylic acid or SA, methyl jasmonate or MeJA), phenolic precursors (p-coumaric acids or CA), and ultraviolet irradiation (UV-C). The influence of these effectors on the levels of 13 VaCBL and 27 VaCIPK mRNA transcripts as well as on stilbene production was analyzed by quantitative real-time RT-PCR in the leaves and cell cultures of V. amurensis. The data revealed that VaCBL4-1 expression considerably increased after UV-C treatment in both grapevine cell cultures and leaves. The expression of VaCIPK31, 41-1, and 41-2 also increased, but this increase was mostly detected in cell cultures of V. amurensis. At the same time, expression of most VaCBL and VaCIPK genes was markedly down-regulated both in leaves and cell cultures of V. amurensis, which may indicate that the CBLs and CIPKs are involved in negative regulation of stilbene accumulation (VaCBL8, 10a-2, 10a-4, 11, 12, VaCIPK3, 9-1, 9-2, 12, 21-1, 21-2, 33, 34, 35, 36, 37, 39, 40, 41-3, 41-4). The results obtained provide new information of CBL and CIPK implication in the regulation of plant secondary metabolism in response to stress hormones, metabolite precursors, and UV-C irradiation.

Resveratrol: Its Path from Isolation to Therapeutic Action in Eye Diseases

Due to the confirmed therapeutic potential of resveratrol (Rv) for eye diseases, namely its powerful anti-angiogenic and antioxidant effects, this molecule must be studied more deeply. Nowadays, the pharmaceutic and pharmacokinetic available studies offer a troubling picture because of its low stability and bioavailability. To overcome this problem, researchers started to design and create different delivery systems that could improve the delivery amount of Rv. Therefore, this review aims to shed light on the proper and efficient techniques to isolate, purify and quantify the Rv molecule, and how this therapeutic molecule can be a part of a delivery system. The Rv great impact on aspects regarding its stability, bioavailability and absorption are also debated here, based on the existent literature on in vitro and in vivo human and animal studies. Moreover, after its absorption the Rv influence at the molecular level in ocular pathologies is described. In addition, the present review summarizes the available literature about Rv, hoping that Rv will gain more attention to investigate its unexplored side.

Chemistry, Biosynthesis and Pharmacology of Viniferin: Potential Resveratrol-Derived Molecules for New Drug Discovery, Development and Therapy

Viniferin is a resveratrol derivative. Resveratrol is the most prominent stilbenoid synthesized by plants as a defense mechanism in response to microbial attack, toxins, infections or UV radiation. Different forms of viniferin exist, including alpha-viniferin (α-viniferin), beta-viniferin (β-viniferin), delta-viniferin (δ-viniferin), epsilon-viniferin (ε-viniferin), gamma-viniferin (γ-viniferin), R-viniferin (vitisin A), and R2-viniferin (vitisin B). All of these forms exhibit a range of important biological activities and, therefore, have several possible applications in clinical research and future drug development. In this review, we present a comprehensive literature search on the chemistry and biosynthesis of and the diverse studies conducted on viniferin, especially with regards to its anti-inflammatory, antipsoriasis, antidiabetic, antiplasmodic, anticancer, anti-angiogenic, antioxidant, anti-melanogenic, neurodegenerative effects, antiviral, antimicrobial, antifungal, antidiarrhea, anti-obesity and anthelminthic activities. In addition to highlighting its important chemical and biological activities, coherent and environmentally acceptable methods for establishing vinferin on a large scale are highlighted to allow the development of further research that can help to exploit its properties and develop new phyto-pharmaceuticals. Overall, viniferin and its derivatives have the potential to be the most effective nutritional supplement and supplementary medication, especially as a therapeutic approach. More researchers will be aware of viniferin as a pharmaceutical drug as a consequence of this review, and they will be encouraged to investigate viniferin and its derivatives as pharmaceutical drugs to prevent future health catastrophes caused by a variety of serious illnesses.

Effect of VaMyb40 and VaMyb60 Overexpression on Stilbene Biosynthesis in Cell Cultures of Grapevine Vitis amurensis Rupr

Stilbenes are plant defense compounds known to rapidly accumulate in grapevine and some other plant species in response to microbial infection and several abiotic stresses. Stilbenes have attracted considerable attention due to valuable biological effects with multi-spectrum therapeutic application. However, there is a lack of information on natural signaling pathways and transcription factors regulating stilbene biosynthesis. It has been previously shown that MYB R2R3 transcription factor genes VaMyb40 and VaMyb60 were up-regulated in cell cultures of wild-growing grapevine Vitis amurensis Rupr. in response to UV irradiation. In this study, the effects of VaMyb40 or VaMyb60 overexpression in cell cultures of V. amurensis on their capability to produce stilbenes were investigated. Overexpression of the VaMyb60 gene led to a considerable increase in the content of stilbenes in three independently transformed transgenic lines in 5.9–13.9 times, while overexpression of the VaMyb40 gene also increased the content of stilbenes, although to a lesser extent (in 3.4–4.0 times) in comparison with stilbene levels in the empty vector-transformed calli. Stilbene content and stilbene production in the VaMyb60-transgenic calli reached 18.8 mg/g of dry weight (DW) and 150.8 mg/L, respectively. Using HPLC analysis, we detected eight individual stilbenes: t-resveratrol diglucoside, t-piceid, t-resveratrol, ε-viniferin, δ-viniferin, cis-resveratrol, cis-piceid, t-piceatannol. T-resveratrol prevailed over other stilbenoid compounds (53.1–89.5% of all stilbenes) in the VaMyb-overexpressing cell cultures. Moreover, the VaMyb40- and VaMyb60-transformed calli were capable of producing anthocyanins up to 0.035 mg/g DW, while the control calli did not produce anthocyanins. These findings show that the VaMyb40 and VaMyb60 genes positively regulate the stilbene biosynthesis as strong positive transcription regulators and can be used in biotechnological applications for stilbene production or high-quality viticulture and winemaking.

Effect of Calmodulin-like Gene (CML) Overexpression on Stilbene Biosynthesis in Cell Cultures of Vitis amurensis Rupr

Stilbenes are plant phenolics known to rapidly accumulate in grapevine and other plants in response to injury or pathogen attack and to exhibit a great variety of healing beneficial effects. It has previously been shown that several calmodulin-like protein (CML) genes were highly up-regulated in cell cultures of wild-growing grapevine Vitis amurensis Rupr. in response to stilbene-modulating conditions, such as stress hormones, UV-C, and stilbene precursors. Both CML functions and stilbene biosynthesis regulation are still poorly understood. In this study, we investigated the effect of overexpression of five VaCML genes on stilbene and biomass accumulation in the transformed cell cultures of V. amurensis. We obtained 16 transgenic cell lines transformed with the VaCML52, VaCML65, VaCML86, VaCML93, and VaCML95 genes (3–4 independent lines per gene) under the control of the double CaMV 35S promoter. HPLC-MS analysis showed that overexpression of the VaCML65 led to a considerable and consistent increase in the content of stilbenes of 3.8–23.7 times in all transformed lines in comparison with the control calli, while biomass accumulation was not affected. Transformation of the V. amurensis cells with other analyzed VaCML genes did not lead to a consistent and considerable effect on stilbene biosynthesis in the cell lines. The results indicate that the VaCML65 gene is implicated in the signaling pathway regulating stilbene biosynthesis as a strong positive regulator and can be useful in viticulture and winemaking for obtaining grape cultivars with a high content of stilbenes and stress resistance.

The Bark of the Spruce Picea jezoensis Is a Rich Source of Stilbenes

Stilbenes are plant phenolic secondary metabolites that show beneficial effects on human health and possess high antifungal activity against plant pathogens. Currently, a search for plant sources with high stilbene levels is relevant, since stilbene content in various plant species can vary substantially and is often at a low level. In this paper, the bark and wood of Picea jezoensis were analyzed for the content and composition of stilbenes and compared with other known stilbene sources. The HPLC-MS analysis of P. jezoensis bark and wood extracted with different solvents and at different temperatures revealed the presence of 11 and 5 stilbenes, respectively. The highest number of stilbenes of 171 and 229 mg per g of the dry weight (mg/g DW) was extracted from the bark of P. jezoensis using methanol or ethanol at 60 °C for 2 h. Trans-astringin, trans-piceid, and trans-isorhapontin prevailed over other stilbenoids (99% of all detected stilbenes). The most abundant stilbene was trans-isorhapontin, reaching 217 mg/g DW or 87% of all stilbenes. An increase in the extraction time from 2 to 6 h did not considerably increase the detected level of stilbenes, while lower extraction temperatures (20 and 40 °C) significantly lowered stilbene yield. The content of stilbenes in the P. jezoensis bark considerably exceeded stilbene levels in other stilbene-producing plant species. The present data revealed that the bark of P. jezoensis is a rich source of stilbenes (primarily trans-isorhapontin) and provided effective stilbene extraction procedures.

Exogenous Stilbenes Improved Tolerance of Arabidopsis thaliana to a Shock of Ultraviolet B Radiation

Excessive ultraviolet B (UV-B) irradiation is one of the most serious threats leading to severe crop production losses. It is known that secondary metabolite biosynthesis plays an important role in plant defense and forms a protective shield against excessive UV-B irradiation. The contents of stilbenes and other plant phenolics are known to sharply increase after UV-B irradiation, but there is little direct evidence for the involvement of stilbenes and other plant phenolics in plant UV-B protection. This study showed that foliar application of trans-resveratrol (1 and 5 mM) and trans-piceid (5 mM) considerably increased tolerance to a shock of UV-B (10 min at 1800 µW cm⁻² of irradiation intensity) of four-week-old Arabidopsis thaliana plants that are naturally incapable of stilbene production. Application of trans-resveratrol and trans-piceid increased the leaf survival rates by 1–2%. This stilbene-induced improvement in UV-B tolerance was higher than after foliar application of the stilbene precursors, p-coumaric and trans-cinnamic acids (only 1–3%), but less than that after treatment with octocrylene (19–24%), a widely used UV-B absorber. Plant treatment with trans-resveratrol increased expression of antioxidant and stress-inducible genes in A.thaliana plants and decreased expression of DNA repair genes. This study directly demonstrates an important positive role of stilbenes in plant tolerance to excessive UV-B irradiation, and offers a new approach for plant UV-B protection.

The Influence of the Grapevine Bacterial and Fungal Endophytes on Biomass Accumulation and Stilbene Production by the In Vitro Cultivated Cells of Vitis amurensis Rupr

Plant endophytes are known to alter the profile of secondary metabolites in plant hosts. In this study, we identified the main bacterial and fungal representatives of the wild grape Vitis amurensis Rupr. microbiome and investigated a cocultivation effect of the 14 endophytes and the V. amurensis cell suspension on biomass accumulation and stilbene biosynthesis. The cocultivation of the V. amurensis cell culture with the bacteria Agrobacterium sp., Bacillus sp., and Curtobacterium sp. for 2 weeks did not significantly affect the accumulation of cell culture fresh biomass. However, it was significantly inhibited by the bacteria Erwinia sp., Pantoea sp., Pseudomonas sp., and Xanthomonas sp. and fungi Alternaria sp., Biscogniauxia sp., Cladosporium sp., Didymella sp. 2, and Fusarium sp. Cocultivation of the grapevine cell suspension with the fungi Didymella sp. 1 and Trichoderma sp. resulted in cell death. The addition of endophytic bacteria increased the total stilbene content by 2.2–5.3 times, while the addition of endophytic fungi was more effective in inducing stilbene accumulation by 2.6–16.3 times. The highest content of stilbenes in the grapevine cells cocultured with endophytic fungi was 13.63 and 13.76 mg/g of the cell dry weight (DW) after cultivation with Biscogniauxia sp. and Didymella sp. 2, respectively. The highest content of stilbenes in the grapevine cells cocultured with endophytic bacteria was 4.49 mg/g DW after cultivation with Xanthomonas sp. The increase in stilbene production was due to a significant activation of phenylalanine ammonia lyase (PAL) and stilbene synthase (STS) gene expression. We also analyzed the sensitivity of the selected endophytes to eight antibiotics, fluconazole, and trans-resveratrol. The endophytic bacteria were sensitive to gentamicin and kanamycin, while all selected fungal strains were resistant to fluconazole with the exception of Cladosporium sp. All endophytes were tolerant of trans-resveratrol. This study showed that grape endophytes stimulate the production of stilbenes in grape cell suspension, which could further contribute to the generation of a new stimulator of stilbene biosynthesis in grapevine or grape cell cultures.

Resveratrol Alleviates the KCl Salinity Stress of Malus hupehensis Rhed

Applying large amounts of potash fertilizer in apple orchards for high apple quality and yield aggravates KCl stress. As a phytoalexin, resveratrol (Res) participates in plant resistance to biotic stress. However, its role in relation to KCl stress has never been reported. Herein we investigated the role of Res in KCl stress response of Malus hupehensis Rehd., a widely used apple rootstock in China which is sensitive to KCl stress. KCl-stressed apple seedlings showed significant wilting phenotype and decline in photosynthetic rate, and the application of 100 μmol Res alleviated KCl stress and maintained photosynthetic capacity. Exogenous Res can strengthen the activities of peroxidase and catalase, thus eliminating reactive oxygen species production induced by KCl stress. Moreover, exogenous Res can decrease the electrolyte leakage by accumulating proline for osmotic balance under KCl stress. Furthermore, exogenous Res application can affect K+/Na+ homeostasis in cytoplasm by enhancing K+ efflux outside the cells, inhibiting Na+ efflux and K+ absorption, and compartmentalizing K+ into vacuoles through regulating the expression of K+ and Na+ transporter genes. These findings provide a theoretical basis for the application of exogenous Res to relieve the KCl stress of apples.

Profile of Stilbenes and Other Phenolics in Fanagoria White and Red Russian Wines

Grapes and wines represent the most important source of edible stilbenes and other phenolic metabolites, which demonstrate a wide range of valuable biological activities. However, there is no information about the profile and content of phenolic compounds in Russian wines. We firstly analyzed phenolics (stilbenes, phenolic acids, and flavonols) in some representatives of Russian wines, including eleven red and seven white Russian wines from Fanagoria, Krasnodarsky Territory. The Russian red wines contained six stilbenes (trans-resveratrol, cis-resveratrol, trans-, cis-piceid, trans-piceatannol, δ-viniferin), while the white wines contained only five stilbenes (cis-resveratrol, trans-, cis-piceid, trans-piceatannol, trans-resveratrol). More than a half of the total stilbenes in the wines (65% of all stilbenes) were presented by trans-piceid and cis-piceid, while trans-resveratrol reached 16% of all the stilbenes. The red wines also contained six phenolic acids and six flavonols, while the white wines contained six phenolic acids and only three flavonols. Myrecitin-3-O-glucoside, quercetin-3-O-glucoside, and myricetin were the major flavonols in the red wines, while dihydroquercetin-3-O-rhamnoside was the major flavonol in the white wines. The red wines contained markedly higher amounts of stilbenes, phenolic acids, and flavonols than the white wines. Thus, the data showed that young red Russian Fanagoria wines represent a rich source of phenolic compounds. The study also revealed that younger wines were more abundant in phenolics, and wine storage for six months in the dark at +10 °C led to a decrease in the total content of phenolics, primarily monomeric stilbenes and quercetin-3-O-glucoside and quercetin flavonols.

Impact of Environmental Factors on Stilbene Biosynthesis

Stilbenes are a small family of polyphenolic secondary metabolites that can be found in several distantly related plant species. These compounds act as phytoalexins, playing a crucial role in plant defense against phytopathogens, as well as being involved in the adaptation of plants to abiotic environmental factors. Among stilbenes, trans-resveratrol is certainly the most popular and extensively studied for its health properties. In recent years, an increasing number of stilbene compounds were subjected to investigations concerning their bioactivity. This review presents the most updated knowledge of the stilbene biosynthetic pathway, also focusing on the role of several environmental factors in eliciting stilbenes biosynthesis. The effects of ultraviolet radiation, visible light, ultrasonication, mechanical stress, salt stress, drought, temperature, ozone, and biotic stress are reviewed in the context of enhancing stilbene biosynthesis, both in planta and in plant cell and organ cultures. This knowledge may shed some light on stilbene biological roles and represents a useful tool to increase the accumulation of these valuable compounds.

Grape Berry Secondary Metabolites and Their Modulation by Abiotic Factors in a Climate Change Scenario-A Review

Temperature, water, solar radiation, and atmospheric CO₂ concentration are the main abiotic factors that are changing in the course of global warming. These abiotic factors govern the synthesis and degradation of primary (sugars, amino acids, organic acids, etc.) and secondary (phenolic and volatile flavor compounds and their precursors) metabolites directly, via the regulation of their biosynthetic pathways, or indirectly, via their effects on vine physiology and phenology. Several hundred secondary metabolites have been identified in the grape berry. Their biosynthesis and degradation have been characterized and have been shown to occur during different developmental stages of the berry. The understanding of how the different abiotic factors modulate secondary metabolism and thus berry quality is of crucial importance for breeders and growers to develop plant material and viticultural practices to maintain high-quality fruit and wine production in the context of global warming. Here, we review the main secondary metabolites of the grape berry, their biosynthesis, and how their accumulation and degradation is influenced by abiotic factors. The first part of the review provides an update on structure, biosynthesis, and degradation of phenolic compounds (flavonoids and non-flavonoids) and major aroma compounds (terpenes, thiols, methoxypyrazines, and C13 norisoprenoids). The second part gives an update on the influence of abiotic factors, such as water availability, temperature, radiation, and CO₂ concentration, on berry secondary metabolism. At the end of the paper, we raise some critical questions regarding intracluster berry heterogeneity and dilution effects and how the sampling strategy can impact the outcome of studies on the grapevine berry response to abiotic factors.

Phytostilbenes as agrochemicals: biosynthesis, bioactivity, metabolic engineering and biotechnology

Covering: 1976 to 2020. Although constituting a limited chemical family, phytostilbenes represent an emblematic group of molecules among natural compounds. Ever since their discovery as antifungal compounds in plants and their ascribed role in human health and disease, phytostilbenes have never ceased to arouse interest for researchers, leading to a huge development of the literature in this field. Owing to this, the number of references to this class of compounds has reached the tens of thousands. The objective of this article is thus to offer an overview of the different aspects of these compounds through a large bibliography analysis of more than 500 articles. All the aspects regarding phytostilbenes will be covered including their chemistry and biochemistry, regulation of their biosynthesis, biological activities in plants, molecular engineering of stilbene pathways in plants and microbes as well as their biotechnological production by plant cell systems.

Characterization of Stilbene Composition in Grape Berries from Wild Vitis Species in Year-To-Year Harvest

Asian and American Vitis species possess a strong potential for crossbreeding programs, owing to their several resistance properties. Stilbenes are phenolic compounds present in grape berries and are well-known for their main role as phytoalexins and resistance to biotic stresses in plants. However, their identification and quantification in grape berries from wild Vitis remains unexplored. A mass spectrometry multiple reaction monitoring method combined with the analysis of pure standards allowed for the unambiguous characterization of 20 stilbenes in the grape berry skin extracts of nine native Vitis species and one cultivated Vitis vinifera species (cv. Cabernet Sauvignon). A main occurrence of monomeric (Z-piceid, E-piceid, E-isorhapontin, and E-astringin), dimeric (E-ε-viniferin, Z-ε-viniferin, and pallidol), and oligomeric (isohopeaphenol and r-viniferin) stilbenes was highlighted. Some stilbenes were clearly characterized for the first time in grape berries, such as the dimers ampelopsin A, E-vitisinol C, and parthenocissin A as well as the tetramers r2-viniferin and r-viniferin. Stilbene composition and content varied widely among several Vitis species and vintage years.

Overexpression of stilbene synthase genes to modulate the properties of plants and plant cell cultures

Plant stilbenes have attracted special attention as they possess valuable health benefits and improve plant resistance to environmental stresses. Stilbenes are synthesized via the phenylpropanoid pathway, where stilbene synthase (STS, EC 2.3.1.95) directly catalyzes the formation of t-resveratrol (monomeric stilbene). This review discusses the features of using STS genes in genetic engineering and plant biotechnology with the purpose to increase plant resistance to environmental stresses and to modify secondary metabolite production.

Metabolic Profile and Evaluation of Biological Activities of Extracts from the Stems of Cissus trifoliata

Cissus trifoliata (L.) L belongs to the Vitaceae family and is an important medicinal plant used in Mexico for the management of infectious diseases and tumors. The present study aimed to evaluate the metabolic profile of the stems of C. trifoliata and to correlate the results with their antibacterial and cytotoxic activities. The hexane extract was analyzed using gas chromatography coupled with mass spectrometry (GC-MS) and the CHCl₃-MeOH and aqueous extracts by ultraperformance liquid chromatography quadrupole time of fly mass spectrometry (UPLC-QTOF-MS). The antibacterial activity was determined by broth microdilution and the cytotoxicity was evaluated using MTS cell proliferation assay. Forty-six metabolites were putatively identified from the three extracts. Overall, terpenes, flavonoids and stilbenes characterize the metabolic profile. No antibacterial activity was found in any extract against the fifteen bacteria strains tested (MIC >500 µg/mL). However, high cytotoxic activity (IC₅₀ ≤ 30 µg/mL) was found in the hexane and aqueous extracts against hepatocarcinoma and breast cancer cells (Hep3B, HepG2 and MCF7). This is the first report of the bioactive compounds of C. trifoliata stems and their antibacterial and cytotoxic properties. The metabolic profile rich in anticancer compounds correlate with the cytotoxic activity of the extracts from the stems of C. trifoliata. This study shows the antitumor effects of this plant used in the traditional medicine and justifies further research of its anticancer activity.

Effect of spruce PjSTS1a, PjSTS2, or PjSTS3 gene overexpression on stilbene biosynthesis in callus cultures of Vitis amurensis Rupr

Stilbenes are natural compounds protecting plants against microbial pathogens and known to possess valuable biologically active properties. In the present study, we established transgenic grapevine callus cell cultures overexpressing three stilbene synthase (STS) genes of spruce Picea jezoensis PjSTS1a, PjSTS2, and PjSTS3. Transformation of Vitis amurensis calli with the PjSTS1a, PjSTS2, and PjSTS3 genes significantly increased total content of stilbenes in 3.6-6, 2.5-2.9, and 4.1-16.1 times, respectively, in comparison with the control calli. The most pronounced positive effect on the accumulation of stilbenes was observed for the PjSTS3-overexpressing calli where the total content of stilbenes was increased up to 3.1 mg/g DW, and the stilbene production reached 25.4 mg/L. These values were higher than those achieved for the grapevine callus cell cultures overexpressing three STS genes from V. amurensis. Thus, transformation of grapevine cell cultures with spruce STS genes with a relatively low degree of homology to the endogenous VaSTSs is a more effective strategy for induction of plant secondary metabolite biosynthesis than using the grapevine genes for the overexpression experiments.

Induction of Transgene Suppression in Plants via External Application of Synthetic dsRNA

Recent investigations show that exogenously applied small interfering RNAs (siRNA) and long double-stranded RNA (dsRNA) precursors can be taken up and translocated in plants to induce RNA interference (RNAi) in the plant or in its fungal pathogen. The question of whether genes in the plant genome can undergo suppression as a result of exogenous RNA application on plant surface is almost unexplored. This study analyzed whether it is possible to influence transcript levels of transgenes, as more prone sequences to silencing, in Arabidopsis genome by direct exogenous application of target long dsRNAs. The data revealed that in vitro synthesized dsRNAs designed to target the gene coding regions of enhanced green fluorescent protein (EGFP) or neomycin phosphotransferase II (NPTII) suppressed their transcript levels in Arabidopsis. The fact that, simple exogenous application of polynucleotides can affect mRNA levels of plant transgenes, opens new opportunities for the development of new scientific techniques and crop improvement strategies.

The effect of ultraviolet-C and precursor feeding on stilbene biosynthesis in spruce Picea jezoensis

This study examines the effects of p-coumaric (CoA) and caffeic (CaA) acids on stilbene biosynthesis in one-year-old needles of Picea jezoensis (Lindl. et Gord.) Fisch ex Carr. under control conditions and after ultraviolet (UV-C) irradiation. HPLC analysis revealed that while UV-C irradiation slightly affected the total stilbene content, CoA and CaA feeding increased the total content of stilbenes by 1.2-1.3-fold. UV-C treatment combined with CoA-feeding of the P. jezoensis cuttings exerted the most pronounced stimulatory effect on stilbene accumulation leading to the total stilbene content of 9.18 mg/g of dry weight or DW. This increase correlated with the elevated transcription of the stilbene synthase PjSTS1a and PjSTS1b genes. UV-C treatment in combination with CaA feeding of P. jezoensis did not considerably influence stilbene content. These results revealed a positive effect of UV-C radiation and phenolic precursors on the content of stilbenes in spruce needles.

Regulation of stilbene biosynthesis in plants

This review analyzes the advances in understanding the natural signaling pathways and environmental factors regulating stilbene biosynthesis. We also discuss the studies reporting on stilbene content and repertoire in plants. Stilbenes, including the most-studied stilbene resveratrol, are a family of phenolic plant secondary metabolites that have been the subject of intensive research due to their valuable pharmaceutical effects and contribution to plant disease resistance. Understanding the natural mechanisms regulating stilbene biosynthesis in plants could be useful for both the development of new plant protection strategies and for commercial stilbene production. In this review, we focus on the environmental factors and cell signaling pathways regulating stilbene biosynthesis in plants and make a comparison with the regulation of flavonoid biosynthesis. This review also analyzes the recent data on stilbene biosynthetic genes and summarizes the available studies reporting on both stilbene content and stilbene composition in different plant families.

Gnetin-C and other resveratrol oligomers with cancer chemopreventive potential

Resveratrol has been extensively studied to investigate its biological effects, including its chemopreventive potential against cancer. Over the past decade, various resveratrol oligomers, both naturally occurring and synthetic, have been described. These resveratrol oligomers result from the polymerization of two or more resveratrol units to form dimers, trimers, tetramers, or even more complex derivatives. Some oligomers appear to have antitumor activities that are similar or superior to monomeric resveratrol. In this review, we discuss resveratrol oligomers with anticancer potential, with emphasis on well-characterized compounds, such as the dimer gnetin-C and other oligomers from Gnetum gnemon, whose safety, pharmacokinetic, and biological activities have been studied in humans.

Glucosylation of Smoke-Derived Volatiles in Grapevine (Vitis vinifera) is Catalyzed by a Promiscuous Resveratrol/Guaiacol Glucosyltransferase

Vinification of grapes (Vitis vinifera) exposed to forest fire smoke can yield unpalatable wine due to the presence of taint compounds from smoke and the release of smoke derived volatiles from their respective glycosides during the fermentation process or in-mouth during consumption. To identify glycosyltransferases (GTs) involved in the formation of glycosidically bound smoke-derived volatiles we performed gene expression analysis of candidate GTs in different grapevine tissues. Second, substrates derived from bushfire smoke or naturally occurring in grapes were screened with the candidate recombinant GTs. A resveratrol GT (UGT72B27) gene, highly expressed in grapevine leaves and berries was identified to be responsible for the production of the phenolic glucosides. UGT72B27 converted the stilbene trans-resveratrol mainly to the 3-O-glucoside. Kinetic analyses yielded specificity constants (k_cat/K_M) of 114, 17, 9, 8, and 2 mM^-1 s^-1 for guaiacol, trans-resveratrol, syringol, methylsyringol, and methylguaiacol, respectively. This knowledge will help to design strategies for managing the risk of producing smoke-affected wines.