Changes in isovitexin-O-glycosylation during the development of young barley plants

Photoprotective Potential of Passiflora Cincinnata Mast. (Passifloraceae) Hydro-Alcoholic Extracts

Passiflora cincinnata is a Passifloraceae typical of the Caatinga, a biome unique to Brazil. It has various pharmacological properties associated with its high flavonoid content. Vitexin, isovitexin, orientin, isoorientin and derivatives are the main chemical and pharmacological markers for this plant. Although flavonoids enriched-extracts have been widely applied in phytocosmetics, especially in sunscreen formulations, the use of P. cincinnata as a photoprotective ingredient remains unexplored. Different hydro-alcoholic extracts were prepared and their antioxidant and photoprotective activities were evaluated by in vitro assays. The most promising extract (Pc-1) was analyzed by HPLC-DAD-ESI-MS/MS. Nine flavonoids were identified as major compounds: isovitexin-7-O-glucoside, isoorientin-2"O-hexoside, orientin, isoorientin, isovitexin-2"-O-glucoside, isovitexin-6"-O-glucoside, isoscoparin and isoquercitrin. Finally, Pc-1 (5 and 10 %, v/v) was incorporated into gel formulations, alone or combined to commercial chemical filters (benzophenone-3 and octyl methoxycinnamate). Formulations containing Pc-1 showed high SPFspectrophotometric values. When combined to commercial filters, Pc-1 (5 %) potentiated their photoprotective efficacy (p<0.05). A physicochemical characterization indicated no incompatibility or signs of instability after extract incorporation. Altogether, these findings encourage the use of Pc-1 as a photoprotective ingredient or co-adjuvant in sunscreens formulations.

BvCGT1-mediated differential distribution of flavonoid C-glycosides contributes to plant's response to UV-B stress

C-glycosides are a predominant class of flavonoids that demonstrate diverse medical properties and plant physiological functions. The chemical stability, structural diversity, and differential aboveground distribution of these compounds in plants make them ideal protectants. However, little is known about the transcriptional regulatory mechanisms that play these diverse roles in plant physiology. In this study, chard was selected from 69 families for its significantly different flavonoid C-glycosides distributions between the aboveground and underground parts to investigate the role and regulatory mechanism of flavonoid C-glycosides in plants. Our results indicate that flavonoid C-glycosides are affected by various stressors, especially UV-B. Through cloning and validation of key biosynthetic genes of flavonoid C-glycosides in chard (BvCGT1), we observed significant effects induced by UV-B radiation. This finding was further confirmed by resistance testing in BvCGT1 silenced chard lines and in Arabidopsis plants with BvCGT1 overexpression. Yeast one-hybrid and dual-luciferase assays were employed to determine the underlying regulatory mechanisms of BvCGT1 in withstanding UV-B stress. These results indicate a potential regulatory role of BvDof8 and BvDof13 in modulating flavonoid C-glycosides content, through their influence on BvCGT1. In conclusion, we have effectively demonstrated the regulation of BvCGT1 by BvDof8 and BvDof13, highlighting their crucial role in plant adaptation to UV-B radiation. Additionally, we have outlined a comprehensive transcriptional regulatory network involving BvDof8 and BvDof13 in response to UV-B radiation.

Variation of Saponarin Content in Barley Sprouts (Hordeum vulgare L.) by Natural Light Shielding: Implication of the Importance of Light Intensity

Saponarin is a functional metabolite produced by barley sprouts, and the mass production of saponarin by this crop is attractive for dietary supplement manufacturing. Light is the most important environmental factor determining plant growth, survival, and the production of secondary metabolites including flavonoids. This study was conducted to investigate the importance of light intensity for saponarin production in barley sprouts using a hydroponic growth system. Light intensity was manipulated by using shielding treatments to 100, 80, 70, and 50% natural sunlight (NS), and crop cultivation was performed on a monthly cycle. We found that the growth rate and biomass of barley sprouts did not differ in response to the shield treatments, whereas the saponarin content did. The highest saponarin content (i.e., from 1329 to 1673 mg 100 g-1) was observed in the 100% NS treatment, and it gradually decreased as light intensity also decreased. Statistical analysis revealed a significant polynomial relationship of saponarin content with cumulative PPFD (R2 = 76%), implying that the absolute total amount of light exposure over the growth period has a large effect on saponarin productivity in a hydroponic facility. Taken together, our results showed that shielding conditions, which are often unintentionally created by the design of cultivation facilities, can adversely affect saponarin production in barley sprouts. In addition, it was confirmed through our findings that light conditions with at least 70% NS in the cultivation facility enable the production of an amount corresponding to the saponarin content of the sprouts (>1000 mg 100 g-1) produced in the open field. Further studies are needed to investigate the underlying physiological and molecular mechanisms responsible for the relationship of saponarin content with light quantity and quality in barley sprouts.

How do barley plants with impaired photosynthetic light acclimation survive under high-light stress?

MAIN CONCLUSION

WHIRLY1 deficient barley plants surviving growth at high irradiance displayed increased non-radiative energy dissipation, enhanced contents of zeaxanthin and the flavonoid lutonarin, but no changes in α-tocopherol nor glutathione. Plants are able to acclimate to environmental conditions to optimize their functions. With the exception of obligate shade plants, they can adjust their photosynthetic apparatus and the morphology and anatomy of their leaves to irradiance. Barley (Hordeum vulgare L., cv. Golden Promise) plants with reduced abundance of the protein WHIRLY1 were recently shown to be unable to acclimatise important components of the photosynthetic apparatus to high light. Nevertheless, these plants did not show symptoms of photoinhibition. High-light (HL) grown WHIRLY1 knockdown plants showed clear signs of exposure to excessive irradiance such as a low epoxidation state of the violaxanthin cycle pigments and an early light saturation of electron transport. These responses were underlined by a very large xanthophyll cycle pool size and by an increased number of plastoglobules. Whereas zeaxanthin increased with HL stress, α-tocopherol, which is another lipophilic antioxidant, showed no response to excessive light. Also the content of the hydrophilic antioxidant glutathione showed no increase in W1 plants as compared to the wild type, whereas the flavone lutonarin was induced in W1 plants. HPLC analysis of removed epidermal tissue indicated that the largest part of lutonarin was presumably located in the mesophyll. Since lutonarin is a better antioxidant than saponarin, the major flavone present in barley leaves, it is concluded that lutonarin accumulated as a response to oxidative stress. It is also concluded that zeaxanthin and lutonarin may have served as antioxidants in the WHIRLY1 knockdown plants, contributing to their survival in HL despite their restricted HL acclimation.

Saponarin, a Di-glycosyl Flavone from Barley (Hordeum vulgare L.): An Effective Compound for Plant Defense and Therapeutic Application

Saponarin (SA) is a major di-C-glycosyl-O-glycosyl flavone, which is predominantly accumulated in the young green leaves of barley (Hordeum vulgare L.), with numerous biological functions in plants, such as protection against environmental stresses. Generally, SA synthesis and its localization in the mesophyll vacuole or leaf epidermis are largely stimulated in response to biotic and abiotic stresses to participate in a plant's defense response. In addition, SA is also credited for its pharmacological properties, such as the regulation of signaling pathways associated with antioxidant and anti-inflammatory responses. In recent years, many researchers have shown the potential of SA to treat oxidative and inflammatory disorders, such as in protection against liver diseases, and reducing blood glucose, along with antiobesity effects. This review aims to highlight natural variations of SA in plants, biosynthesis pathway, and SA's role in response to environmental stress and implications in various therapeutic applications. In addition, we also discuss the challenges and knowledge gaps concerning SA use and commercialization.

Variability of Properties Modulating the Biosynthesis of Biologically Active Compounds in Young Barley Treated with Ozonated Water

This paper presents the effects of irrigating barley plants with different type of water solutions saturated with gaseous ozone generated from atmospheric air. The study investigated the effects of the applied types of water on the modulation of the biosynthesis of selected bioactive compounds (content of total polyphenols, small molecule antioxidants, vitamin C) in the produced plant material. A number of transformations of reactive oxygen species (ROS) and nitrogen compounds have also been postulated; these are observed during the saturation of water with gaseous O₃ and 30 min after the end of the process. It was shown that after the process of water saturation with gaseous O₃, the gas later is converted to compounds with high oxidative potential and good stability; these, in turn, lead to the oxidation of oxidates generated from atmospheric nitrogen into nitrates, which exhibit fertilising properties. Thirty minutes after the process of H₂O saturation with gaseous O₃ was completed, the tests showed the highest concentrations of nitrates and the relatively high oxidative potential of the solution originating from H₂O₂ with a low concentration of the dissolved O₃. This solution exhibited the highest activity modulating the biosynthesis of polyphenols, small molecule antioxidants and vitamin C in young barley plants. The resulting differences were significant, and they were reflected by 15% higher total polyphenol content, 35% higher antioxidative potential and 57% greater content of vitamin C compared to the control specimens (plants treated with fresh H₂O).

Light Drives and Temperature Modulates: Variation of Phenolic Compounds Profile in Relation to Photosynthesis in Spring Barley

Accumulation and metabolic profile of phenolic compounds (PheCs; serving as UV-screening pigments and antioxidants) as well as carbon fixation rate (A_n) and plant growth are sensitive to irradiance and temperature. Since these factors are naturally co-acting in the environment, it is worthy to study the combined effects of these environmental factors to assess their possible physiological consequences. We investigated how low and high irradiance in combination with different temperatures modify the metabolic profile of PheCs and expression of genes involved in the antioxidative enzyme and PheCs biosynthesis, in relation to photosynthetic activity and availability of non-structural carbohydrates (NSC) in spring barley seedlings. High irradiance positively affected A_n, NSC, PheCs content, and antioxidant activity (AOX). High temperature led to decreased A_n, NSC, and increased dark respiration, whilst low temperature was accompanied by reduction of UV-A shielding but increase of PheCs content and AOX. Besides that, irradiance and temperature caused changes in the metabolic profile of PheCs, particularly alteration in homoorientin/isovitexin derivatives ratio, possibly related to demands on AOX-based protection. Moreover, we also observed changes in the ratio of sinapoyl-/feruloyl- acylated flavonoids, the function of which is not yet known. The data also strongly suggested that the NSC content may support the PheCs production.

Targeted and Untargeted Metabolomic Analyses Reveal Organ Specificity of Specialized Metabolites in the Model Grass Brachypodium distachyon

Brachypodium distachyon, because of its fully sequenced genome, is frequently used as a model grass species. However, its metabolome, which constitutes an indispensable element of complex biological systems, remains poorly characterized. In this study, we conducted comprehensive, liquid chromatography-mass spectrometry (LC-MS)-based metabolomic examination of roots, leaves and spikes of Brachypodium Bd21 and Bd3-1 lines. Our pathway enrichment analysis emphasised the accumulation of specialized metabolites representing the flavonoid biosynthetic pathway in parallel with processes related to nucleotide, sugar and amino acid metabolism. Similarities in metabolite profiles between both lines were relatively high in roots and leaves while spikes showed higher metabolic variance within both accessions. In roots, differences between Bd21 and Bd3-1 lines were manifested primarily in diterpenoid metabolism, while differences within spikes and leaves concerned nucleotide metabolism and nitrogen management. Additionally, sulphate-containing metabolites differentiated Bd21 and Bd3-1 lines in spikes. Structural analysis based on MS fragmentation spectra enabled identification of 93 specialized metabolites. Among them phenylpropanoids and flavonoids derivatives were mainly determined. As compared with closely related barley and wheat species, metabolic profile of Brachypodium is characterized with presence of threonate derivatives of hydroxycinnamic acids.

Unraveling metabolic patterns and molecular mechanisms underlying storability in sugar beet

BACKGROUND

Sugar beet is an important crop for sugar production. Sugar beet roots are stored up to several weeks post-harvest waiting for processing in the sugar factories. During this time, sucrose loss and invert sugar accumulation decreases the final yield and processing quality. To improve storability, more information about post-harvest metabolism is required. We investigated primary and secondary metabolites of six sugar beet varieties during storage. Based on their variety-specific sucrose loss, three storage classes representing well, moderate, and bad storability were compared. Furthermore, metabolic data were visualized together with transcriptome data to identify potential mechanisms involved in the storage process.

RESULTS

We found that sugar beet varieties that performed well during storage have higher pools of 15 free amino acids which were already observable at harvest. This storage class-specific feature is visible at harvest as well as after 13 weeks of storage. The profile of most of the detected organic acids and semi-polar metabolites changed during storage. Only pyroglutamic acid and two semi-polar metabolites, including ferulic acid, show higher levels in well storable varieties before and/or after 13 weeks of storage. The combinatorial OMICs approach revealed that well storable varieties had increased downregulation of genes involved in amino acid degradation before and after 13 weeks of storage. Furthermore, we found that most of the differentially genes involved in protein degradation were downregulated in well storable varieties at both timepoints, before and after 13 weeks of storage.

CONCLUSIONS

Our results indicate that increased levels of 15 free amino acids, pyroglutamic acid and two semi-polar compounds, including ferulic acid, were associated with a better storability of sugar beet taproots. Predictive metabolic patterns were already apparent at harvest. With respect to elongated storage, we highlighted the role of free amino acids in the taproot. Using complementary transcriptomic data, we could identify potential underlying mechanisms of sugar beet storability. These include the downregulation of genes for amino acid degradation and metabolism as well as a suppressed proteolysis in the well storable varieties.

Untargeted metabotyping to study phenylpropanoid diversity in crop plants

Plant genebanks constitute a key resource for breeding to ensure crop yield under changing environmental conditions. Because of their roles in a range of stress responses, phenylpropanoids are promising targets. Phenylpropanoids comprise a wide array of metabolites; however, studies regarding their diversity and the underlying genes are still limited for cereals. The assessment of barley diversity via genotyping-by-sequencing is in rapid progress. Exploring these resources by integrating genetic association studies to in-depth metabolomic profiling provides a valuable opportunity to study barley phenylpropanoid metabolism; but poses a challenge by demanding large-scale approaches. Here, we report an LC-PDA-MS workflow for barley high-throughput metabotyping. Without prior construction of a species-specific library, this method produced phenylpropanoid-enriched metabotypes with which the abundance of putative metabolic features was assessed across hundreds of samples in a single-processed data matrix. The robustness of the analytical performance was tested using a standard mix and extracts from two selected cultivars: Scarlett and Barke. The large-scale analysis of barley extracts showed (1) that barley flag leaf profiles were dominated by glycosylation derivatives of isovitexin, isoorientin, and isoscoparin; (2) proved the workflow's capability to discriminate within genotypes; (3) highlighted the role of glycosylation in barley phenylpropanoid diversity. Using the barley S42IL mapping population, the workflow proved useful for metabolic quantitative trait loci purposes. The protocol can be readily applied not only to explore the barley phenylpropanoid diversity represented in genebanks but also to study species whose profiles differ from those of cereals: the crop Helianthus annuus (sunflower) and the model plant Arabidopsis thaliana.

Changes in Beneficial C-glycosylflavones and Policosanol Content in Wheat and Barley Sprouts Subjected to Differential LED Light Conditions

The spectral quality and intensity of light, photoperiodism, and other environmental factors have profound impacts on the metabolic composition of light-dependent higher plants. Hence, we investigate the effects of fluorescent light (96 μmol m-2s-1) and white (100 μmol m-2s-1), blue (100 μmol m-2s-1), and red (93 μmol m-2s-1) light-emitting diode (LED) light irradiation on the C-glycosylflavone and policosanol contents in young seedlings of wheat and barley. Ultra-high-performance liquid chromatography (UHPLC) analyses of C-glycosylflavone contents in barley reveal that the saponarin content is significantly enhanced under blue LED light irradiation. Under similar conditions, isoorientin and isoschaftoside contents are improved in wheat seedlings. The contents of these C-glycosylflavones differed along with the light quality and growth period. The highest accumulation was observed in sprouts after three days under blue LED light irradiation. GC/MS analyses of policosanol contents showed that 1-hexacosanol (C26:o-OH) in barley and 1-octacosanol (C28:o-OH) in wheat seedlings were reduced under LED light irradiation, compared to seedlings under fluorescent light conditions. Nonetheless, the policosanol contents gradually improved with the extension of growth times and treatments, irrespective of the light quality. Additionally, a positive correlation was observed between the expression pattern of biosynthesis-related genes and the respective metabolite content in barley. This study demonstrates that blue LED light irradiation is useful in maximizing the C-glycosylflavone content in barley and wheat sprouts.

Phenolic Metabolites from Barley in Contribution to Phenome in soil Moisture Deficit

Eight barley varieties from Europe and Asia were subjected to moisture deficit at various development stages. At the seedling stage and the flag leaf stage combined stress was applied. The experiment was designed for visualization of the correlation between the dynamics of changes in phenolic compound profiles and the external phenome. The most significant increase of compound content in water deficiency was observed for chrysoeriol and apigenin glycoconjugates acylated with methoxylated hydroxycinnamic acids that enhanced the UV-protection effectiveness. Moreover, other good antioxidants such as derivatives of luteolin and hordatines were also induced by moisture deficit. The structural diversity of metabolites of the contents changed in response to water deficiency in barley indicates their multipath activities under stress. Plants exposed to moisture deficit at the seedling stage mobilized twice as many metabolites as plants exposed to this stress at the flag leaf stage. Specific metabolites such as methoxyhydroxycinnamic acids participated in the long-term acclimation. In addition, differences in phenolome mobilization in response to moisture deficit applied at the vegetative and generative phases were correlated with the phenotypical consequences. Observations of plant yield and biomass gave us the possibility to discuss the developmentally related consequences of moisture deficit for plants' fitness.

Hydroxycinnamic acids in sunflower leaves serve as UV-A screening pigments

Despite the weak absorption of hydroxycinnamic acids in the UV-A region, we found evidence that these compounds protect against damage induced by UV-A radiation in sunflowers.

Sulfate supply enhances cadmium tolerance in Vicia faba L. plants

Sulfur deficiency and cadmium (Cd) pollution are two ubiquitous constraints affecting plant growth in agricultural soils. However, facing the situation of sulfur deficiency, whether surplus sulfate supply can affect Cd toxicity in plants is still unclear. Therefore, in the present study, experiments with deficient, sufficient, and excess sulfate levels under Cd stress were conducted in faba bean plants hydroponically. We found that sulfate supply significantly increased biomass of Cd-stressed plants when compared with deficient sulfate treatment. Intriguingly, sulfate application also increased Cd concentrations in leaves. Based on increased Cd concentrations without retarding plant growth, we conclude that sulfate supply enhances Cd tolerance in faba bean plants. Sulfate application increased CdSO₄⁰ proportion in the growth medium which is partially related to the increase of Cd in plants because the diffusion of CdSO₄⁰ is faster than Cd²⁺ in plants. Further study on Cd localization showed that this heavy metal was prone to accumulate in the epidermis of leaves as affected by sulfate which might contribute to enhancement of Cd tolerance. Oxidative stress induced by Cd toxicity was alleviated by surplus sulfate supply compared with deficient sulfate. Although capacities of total antioxidants were increased by sulfate in Cd-stressed plants, phenolic compounds as one kind of important antioxidants were unchanged, suggesting that sulfate has no effect on phenolic compounds for scavenging ROS under Cd stress. Taken together, sulfate accelerates Cd accumulation in the epidermis of leaves in faba bean giving rise to higher Cd tolerance.