Foliar application of nettle and Japanese knotweed extracts on Vitis vinifera: impact on phenylpropanoid biosynthesis and antioxidant activity during veraison and harvest of cv. Touriga Franca

BACKGROUND

Plant-based extracts have been recently used as sustainable tools to improve biotic and abiotic stress tolerance and increase grape (Vitis vinifera L.) quality. However, knowledge about the effect of these extracts on secondary metabolism compounds, that are fundamental for grape and wine quality, is still scarce. In this study, a trial was installed in an experimental vineyard with the variety Touriga Franca located at University of Trás-os-Montes e Alto Douro, Baixo Corgo sub-region of the Douro Demarcated Region, Portugal in two growing seasons: 2019 and 2020. The aim was to evaluate the effect of foliar application of nettle (Urtica spp.) extract (NE) and Japanese knotweed (Reynoutria japonica) extract (JKE) on grapevines leaves and berries bioactive compounds contents and antioxidant activity, at veraison and harvest.

RESULTS

The application of NE increased the total carotenoids in leaves and the total phenolics content and the antioxidant activity (ferric reducing antioxidant power, FRAP) in berries while JKE increased flavonoids content in leaves and the antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH) in berries.

CONCLUSION

These extracts seem to have a stimulatory effect on grapevine, enhancing bioactive compounds contents and antioxidant capacity and, consequently, the physiological performance of the plant and the quality of the berries. © 2024 Society of Chemical Industry.

[Site-directed mutagenesis enhances the activity of benzylidene acetone synthase of polyketide synthase from Polygonum cuspidatum]

Polygonum cuspidatum polyketide synthase 1 (PcPKS1) has the catalytic activity of chalcone synthase (CHS) and benzylidene acetone synthase (BAS), which can catalyze the production of polyketides naringenin chalcone and benzylidene acetone, and then catalyze the synthesis of flavonoids or benzylidene acetone. In this study, three amino acid sites (Thr133, Ser134, Ser33) that may affect the function of PcPKS1 were identified by analyzing the sequences of PcPKS1, the BAS from Rheum palmatum and the CHS from Arabidopsis thaliana, as well as the conformation of the catalytic site of the enzyme. Molecular modification of PcPKS1 was carried out by site-directed mutagenesis, and two mutants were successfully obtained. The in vitro enzymatic reactions were carried out, and the differences in activity were detected by high performance liquid chromatography (HPLC). Finally, mutants T133LS134A and S339V with bifunctional activity were obtained. In addition to bifunctional activities of BAS and CHS, the modified PcPKS1 had much higher BAS activity than that of the wild type PcPKS1 under the conditions of pH 7.0 and pH 9.0, respectively. It provides a theoretical basis for future use of PcPKS1 in genetic engineering to regulate the biosynthesis of flavonoids and raspberry ketones.

PcWRKY11, an II-d WRKY Transcription Factor from Polygonum cuspidatum, Enhances Salt Tolerance in Transgenic Arabidopsis thaliana

Being an invasive plant, Polygonum cuspidatum is highly resilient and can survive in unfavorable environments for long periods; however, its molecular mechanisms associated with such environmental resistance are largely unknown. In this study, a WRKY transcription factor (TF) gene, PcWRKY11, was identified from P. cuspidatum by analyzing methyl jasmonate (MeJA)-treated transcriptome data. It showed a high degree of homology with WRKY11 from Arabidopsis thaliana, containing a WRKY domain and a zinc finger structure and II-d WRKY characteristic domains of HARF, a calmodulin-binding domain (C-motif), and a putative nuclear localization signal (NLS) through sequence alignment and functional element mining. qPCR analysis showed that the expression of PcWRKY11 can be induced by NaCl, osmotic stress, and UV-C. In this study, we also found that overexpression of PcWRKY11 in A. thaliana could significantly increase salt tolerance. To explore its possible molecular mechanism, further investigations showed that compared with the wild type (WT), under salt stress, the transgenic plants showed a lower malondialdehyde (MDA) content, higher expression of ascorbate peroxidase (APX) and superoxide dismutase (SOD), and higher enzyme activity of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Moreover, the transgenic plants also showed higher expression of Δ¹-pyrroline-5-carboxylate synthase (AtP5CS), and higher contents of proline and soluble sugar. Taken together, these results indicate that PcWRKY11 may have a positive role in plants’ adaptation to salinity conditions by reducing reactive oxygen species (ROS) levels and increasing osmosis substance synthesis.

Molecular Analysis of UV-C Induced Resveratrol Accumulation in Polygonum cuspidatum Leaves

Resveratrol is one of the most studied plant secondary metabolites owing to its numerous health benefits. It is accumulated in some plants following biotic and abiotic stress pressures, including UV-C irradiation. Polygonum cuspidatum represents the major natural source of concentrated resveratrol but the underlying mechanisms as well as the effects of UV-C irradiation on resveratrol content have not yet been documented. Herein, we found that UV-C irradiation significantly increased by 2.6-fold and 1.6-fold the resveratrol content in irradiated leaf samples followed by a dark incubation for 6 h and 12 h, respectively, compared to the untreated samples. De novo transcriptome sequencing and assembly resulted into 165,013 unigenes with 98 unigenes mapped to the resveratrol biosynthetic pathway. Differential expression analysis showed that P.cuspidatum strongly induced the genes directly involved in the resveratrol synthesis, including phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate-CoA ligase and stilbene synthase (STS) genes, while strongly decreased the chalcone synthase (CHS) genes after exposure to UV-C. Since CHS and STS share the same substrate, P. cuspidatum tends to preferentially divert the substrate to the resveratrol synthesis pathway under UV-C treatment. We identified several members of the MYB, bHLH and ERF families as potential regulators of the resveratrol biosynthesis genes.

Tolerance of Japanese knotweed s.l. to soil artificial polymetallic pollution: early metabolic responses and performance during vegetative multiplication

The expansion of invasive Japanese knotweed s.l. is of particular concern because of its aptitudes to rapidly colonize diverse environments, especially anthropized habitats generally characterized by their pollution with heavy metals. Whether the presence of heavy metals impacts the performance traits of this plant is a central question to better understand its invasive properties, though no controlled approach to assess these effects was yet reported. In this aim, we undertook greenhouse experiments where rhizome fragments of Japanese knotweed s.l. (Fallopia japonica and Fallopia × bohemica) were grown during 1 and 3 months, in a soil pot artificially polluted or not with heavy metals added in mixture (Cd, Cr, Pb, Zn). Our results showed that (i) the presence of heavy metals delayed rhizome regeneration and induced lowered plant part weights but did not affect plant height after 3 months; (ii) the effect of metals on the metabolic profiles of belowground part extracts was only detectable after 1 month and not after 3 months of growth, though it was possible to highlight the effect of metals independently of time and genotype for root extracts, and torosachrysone seemed to be the most induced compound; and (iii) the hybrid genotype tested was able to accumulate relatively high concentrations of metals, over or close to the highest reported ones for this plant for Cr, Cd and Zn, whereas Pb was not accumulated. These findings evidence that the presence of heavy metals in soil has a low impact on Fallopia sp. overall performance traits during rhizome regeneration, and has a rather stimulating effect on plant growth depending on pollution level.

Polydatin Restores Endothelium-Dependent Relaxation in Rat Aorta Rings Impaired by High Glucose: A Novel Insight into the PPARβ-NO Signaling Pathway

Polydatin, a natural component from Polygonum Cuspidatum, has important therapeutic effects on metabolic syndrome. A novel therapeutic strategy using polydatin to improve vascular function has recently been proposed to treat diabetes-related cardiovascular complications. However, the biological role and molecular basis of polydatin’s action on vascular endothelial cells (VECs)-mediated vasodilatation under diabetes-related hyperglycemia condition remain elusive. The present study aimed to assess the contribution of polydatin in restoring endothelium-dependent relaxation and to determine the details of its underlying mechanism. By measuring endothelium-dependent relaxation, we found that acetylcholine-induced vasodilation was impaired by elevated glucose (55 mmol/L); however, polydatin (1, 3, 10 μmol/L) could restore the relaxation in a dose-dependent manner. Polydatin could also improve the histological damage to endothelial cells in the thoracic aorta. Polydatin’s effects were mediated via promoting the expression of endothelial NO synthase (eNOS), enhancing eNOS activity and decreasing the inducible NOS (iNOS) level, finally resulting in a beneficial increase in NO release, which probably, at least in part, through activation of the PPARβ signaling pathway. The results provided a novel insight into polydatin action, via PPARβ-NO signaling pathways, in restoring endothelial function in high glucose conditions. The results also indicated the potential utility of polydatin to treat diabetes related cardiovascular diseases.

Quality assessment of Japanese knotweed (Fallopia japonica) grown on Prince Edward Island as a source of resveratrol

Japanese knotweed (Fallopia japonica , also known as Polygonum cuspidatum) is a common invasive plant species on Prince Edward Island (PEI), Canada, whereas it has been used in Chinese medicine and more recently as a raw material for extracting resveratrol. This paper reports on the quantification of resveratrol, polydatin, emodin, and physcion in roots, stems, and leaves of Japanese knotweed samples from PEI and British Columbia (BC), Canada, and nine provinces of China, by ultraperformance liquid chromatography (UPLC). The results showed that the root contains a much higher level of resveratrol than the stem and leaf, and it is accumulated in its highest level in October. PEI-grown knotweed contains similar levels of resveratrol and polydatin compared to Chinese samples collected in the month of October, but the contents of the other anthraquinones (emodin and physcion) are different. As such, Japanese knotweed grown in PEI could be a commercially viable source of raw material for resveratrol production; however, caution has to be taken in harvesting the right plant species.

Biotransformation of polydatin to resveratrol in Polygonum cuspidatum roots by highly immobilized edible Aspergillus niger and Yeast

A new biotransformation method of producing resveratrol with co-immobilized edible Aspergillus niger and Yeast (AY) was investigated. The biotransformation conditions were optimized for the resveratrol production under 30 °C, pH 6.5, 2 days, liquid-solid ratio 12:1 (mL/g), the yield of resveratrol reached 33.45 mg/g, which increased 11-fold to that of untreated one. The conversion rate of polydatin reached 96.7%. The residual activity of immobilized microorganism was 83.2% after used for 15 runs. The developed method could be an effectively alternative biotransformation method for producing resveratrol from the plants.

Quality assessment of Polygonum cuspidatum and Polygonum multiflorum by 1H NMR metabolite fingerprinting and profiling analysis

The quality assessment and control of traditional Chinese medicines (TCM) nowadays receives a great deal of attention worldwide and particularly in Europe with its increasing local use. Polygonum cuspidatum Siebold & Zucc. and Polygonum multiflorum Thunb. are two members of the Polygonaceae family, which are widely used as Chinese medicinal plants. The aim of this study was to achieve an overview of the quality of P. cuspidatum and P. multiflorum samples available on the Chinese market and to identify important metabolites for their discrimination, using (1)H NMR-based metabolomics. (1)H NMR and multivariate analysis techniques were applied to almost 60 plant samples collected in different places in China. Using (1)H NMR metabolomics, it was possible, without previous evaporation or separation steps, to obtain metabolic fingerprints to distinguish between the species. The important metabolites for discrimination were stilbene derivatives. Finally, a clear distinction between the two species was possible and the discriminant metabolites were identified.

[Increasing the content of active constituents in Polygonum cuspidatum hairy root by gene transformation technology]

To increase the content of active constituent--RE and PD of Polygonum cuspidatum hairy root, through Ri-mediated gene transformation technology, modified high salt low pH method was used to distill genome DNA of grapevine (Vitis raparia). Primer was designed according to sequence of Genebank (AF128861). Through PCR amplification obtain RS gene sequence was obtained. Binary vector pCAMBIA1300-35S-RS was constructed. Frost thawing method was used to transform Agrobacterium rhizogenes ATCC11325. Scratched aseptic seedling leaf of Polygonum cuspidatum was contaminated subsequently. DNA conformity and mRNA expression of RS gene were investigated by PCR and RT-PCR respectively. RE and PD in transgenic hairy root were determined by HPLC. For the first time successfully inducement acquires transformed RS gene hairy root of Polygonum cuspidatum. Content of active constituents--RE and PD were 17 - 187 microg x g(-1) DW and 836 - 1 970 microg x g(-1) DW, respectively, the non-transgenic hairy root was 0 - 130 microg x g(-1) DW and 190 - 320 microg x g(-1) DW. In the different root selected, the content of PD was much higher than that in non-transformed hairy roots of Polygonum cuspidatum, the highest content is 5 times, but the content of RE has not increased apparently.

Biotransformation of piceid in Polygonum cuspidatum to resveratrol by Aspergillus oryzae

Biotransformation of piceid in Polygonum cuspidatum to resveratrol by Aspergillus oryzae was investigated in this study. Resveratrol is widely used in medicine, food, and cosmetic because of its pharmacological properties. However, it has a much lower content in plants compared with its glucoside piceid, which has a much lower bioavailability. Traditionally, the aglycone is acquired by acid or enzymatic hydrolysis of its glucoside, but the violent condition and the acid pollution in hydrolytic reaction and the high cost of the enzyme limit their industrial development. In this paper, fermentation of P. cuspidatum by A. oryzae was successfully performed, during which, piceid was converted to resveratrol with the highest yield of trans-resveratrol 1.35%, 3.6 times higher than that obtained from raw herb by microwave-assisted extraction. Scale-up production was also performed and the yield of trans-resveratrol was 3.1 times higher after 24 h incubation. Therefore, biotransformation is a better method to increase the yield of resveratrol because of its high yield and mild conditions.

Seasonal change in the balance between capacities of RuBP carboxylation and RuBP regeneration affects CO2 response of photosynthesis in Polygonum cuspidatum

The balance between the capacities of RuBP (ribulose-1,5-bisphosphate) carboxylation (V(cmax)) and RuBP regeneration (expressed as the maximum electron transport rate, J(max)) determines the CO(2) dependence of the photosynthetic rate. As it has been suggested that this balance changes depending on the growth temperature, the hypothesis that the seasonal change in air temperature affects the balance and modulates the CO(2) response of photosynthesis was tested. V(cmax) and J(max) were determined in summer and autumn for young and old leaves of Polygonum cuspidatum grown at two CO(2) concentrations (370 and 700 micromol mol(-1)). Elevated CO(2) concentration tended to reduce both V(cmax) and J(max) without changing the J(max):V(cmax) ratio. The seasonal environment, on the other hand, altered the ratio such that the J(max):V(cmax) ratio was higher in autumn leaves than summer leaves. This alternation made the photosynthetic rate more dependent on CO(2) concentration in autumn. Therefore, when photosynthetic rates were compared at growth CO(2) concentration, the stimulation in photosynthetic rate was higher in young-autumn than in young-summer leaves. In old-autumn leaves, the stimulation of photosynthesis brought by a change in the J(max):V(cmax) ratio was partly offset by accelerated leaf senescence under elevated CO(2). Across the two seasons and the two CO(2) concentrations, V(cmax) was strongly correlated with Rubisco and J(max) with cytochrome f content. These results suggest that seasonal change in climate affects the relative amounts of photosynthetic proteins, which in turn affect the CO(2) response of photosynthesis.