Flavonoids and Isoflavonoids Biosynthesis in the Model Legume Lotus japonicus; Connections to Nitrogen Metabolism and Photorespiration

Phytoestrogens: Chemistry, potential health benefits, and their medicinal importance

Phytoestrogens, also known as xenoestrogens, are secondary metabolites derived from plants that have similar structures and biological effects as human estrogens. These compounds do not directly affect biological functions but can act as agonists or antagonists depending on the level of endogenous estrogen in the body. Phytoestrogens may have an epigenetic mechanism of action independent of estrogen receptors. These compounds are found in more than 300 plant species and are synthesized through the phenylpropanoid pathway, with specific enzymes leading to various chemical structures. Phytoestrogens, primarily phenolic compounds, include isoflavonoids, flavonoids, stilbenes, and lignans. Extensive research in animals and humans has demonstrated the protective effects of phytoestrogens on estrogen-dependent diseases. Clinical trials have also shown their potential benefits in conditions such as osteoporosis, Parkinson's disease, and certain types of cancer. This review provides a concise overview of phytoestrogen classification, chemical diversity, and biosynthesis and discusses the potential therapeutic effects of phytoestrogens, as well as their preclinical and clinical development.

Transcriptome Analysis of Sesame (Sesamum indicum L.) Reveals the LncRNA and mRNA Regulatory Network Responding to Low Nitrogen Stress

Nitrogen is one of the important factors restricting the development of sesame planting and industry in China. Cultivating sesame varieties tolerant to low nitrogen is an effective way to solve the problem of crop nitrogen deficiency. To date, the mechanism of low nitrogen tolerance in sesame has not been elucidated at the transcriptional level. In this study, two sesame varieties Zhengzhi HL05 (ZZ, nitrogen efficient) and Burmese prolific (MD, nitrogen inefficient) in low nitrogen were used for RNA-sequencing. A total of 3964 DEGs (differentially expressed genes) and 221 DELs (differentially expressed lncRNAs) were identified in two sesame varieties at 3d and 9d after low nitrogen stress. Among them, 1227 genes related to low nitrogen tolerance are mainly located in amino acid metabolism, starch and sucrose metabolism and secondary metabolism, and participate in the process of transporter activity and antioxidant activity. In addition, a total of 209 pairs of lncRNA-mRNA were detected, including 21 pairs of trans and 188 cis. WGCNA (weighted gene co-expression network analysis) analysis divided the obtained genes into 29 modules; phenotypic association analysis identified three low-nitrogen response modules; through lncRNA-mRNA co-expression network, a number of hub genes and cis/trans-regulatory factors were identified in response to low-nitrogen stress including GS1-2 (glutamine synthetase 1-2), PAL (phenylalanine ammonia-lyase), CHS (chalcone synthase, CHS), CAB21 (chlorophyll a-b binding protein 21) and transcription factors MYB54, MYB88 and NAC75 and so on. As a trans regulator, lncRNA MSTRG.13854.1 affects the expression of some genes related to low nitrogen response by regulating the expression of MYB54, thus responding to low nitrogen stress. Our research is the first to provide a more comprehensive understanding of DEGs involved in the low nitrogen stress of sesame at the transcriptome level. These results may reveal insights into the molecular mechanisms of low nitrogen tolerance in sesame and provide diverse genetic resources involved in low nitrogen tolerance research.

Deciphering the regulatory networks involved in mild and severe salt stress responses in the roots of wild grapevine Vitis vinifera spp. sylvestris

Transcriptional regulatory networks are pivotal components of plant's response to salt stress. However, plant adaptation strategies varied as a function of stress intensity, which is mainly modulated by climate change. Here, we determined the gene regulatory networks based on transcription factor (TF) TF_gene co-expression, using two transcriptomic data sets generated from the salt-tolerant "Tebaba" roots either treated with 50 mM NaCl (mild stress) or 150 mM NaCl (severe stress). The analysis of these regulatory networks identified specific TFs as key regulatory hubs as evidenced by their multiple interactions with different target genes related to stress response. Indeed, under mild stress, NAC and bHLH TFs were identified as central hubs regulating nitrogen storage process. Moreover, HSF TFs were revealed as a regulatory hub regulating various aspects of cellular metabolism including flavonoid biosynthesis, protein processing, phenylpropanoid metabolism, galactose metabolism, and heat shock proteins. These processes are essentially linked to short-term acclimatization under mild salt stress. This was further consolidated by the protein-protein interaction (PPI) network analysis showing structural and plant growth adjustment. Conversely, under severe salt stress, dramatic metabolic changes were observed leading to novel TF members including MYB family as regulatory hubs controlling isoflavonoid biosynthesis, oxidative stress response, abscisic acid signaling pathway, and proteolysis. The PPI network analysis also revealed deeper stress defense changes aiming to restore plant metabolic homeostasis when facing severe salt stress. Overall, both the gene co-expression and PPI network provided valuable insights on key transcription factor hubs that can be employed as candidates for future genetic crop engineering programs.

Comparative physiological and transcriptomic analysis reveals an improved biological control efficacy of Sporidiobolus pararoseus Y16 enhanced with ascorbic acid against the oxidative stress tolerance caused by Penicillium expansum in pears

Sporidiobolus pararoseus Y16, a species of significant ecological importance, has distinctive physiological and biological regulatory systems that aid in its survival and environmental adaptation. The goal of this investigation was to understand the complex interactions between physiological and molecular mechanisms in pear fruits as induced by S. pararoseus Y16. The study investigated the use of S. pararoseus Y16 and ascorbic acid (VC) in combination in controlling blue mold decay in pears via physiological and transcriptomic approach. The study results showed that treatment of S. pararoseus Y16 with 150 μg/mL VC reduced pears blue mold disease incidence from 43% to 11%. Furthermore, the combination of S. pararoseus Y16 and VC significantly inhibited mycelia growth and spore germination of Penicillium expansum in the pear's wounds. The pre-treatment did not impair post-harvest qualities of pear fruit but increased antioxidant enzyme activity specifically polyphenol oxidase (PPO), peroxidase (POD), catalase (CAT) activities as well as phenylalanine ammonia-lyase (PAL) enzyme activity. The transcriptome analysis further uncovered 395 differentially expressed genes (DEGs) and pathways involved in defense mechanisms and disease resistance. Notable pathways of the DEGs include plant-pathogen interaction, tyrosine metabolism, and hormone signal transduction pathways. The integrative approach with both physiological and transcriptomic tools to investigate postharvest pathology in pear fruits with clarification on how S. pararoseus Y16 enhanced with VC, improved gene expression for disease defense, and create alternative controls strategies for managing postharvest diseases.

Plant Growth-Promoting Rhizobacteria Are Key to Promoting the Growth and Furanocoumarin Synthesis of Angelica dahurica var. formosana under Low-Nitrogen Conditions

Microbiomes are the most important members involved in the regulation of soil nitrogen metabolism. Beneficial interactions between plants and microbiomes contribute to improving the nitrogen utilization efficiency. In this study, we investigated the Apiaceae medicinal plant Angelica dahurica var. formosana. We found that under a low-nitrogen treatment, the abundance of carbon metabolites in the rhizosphere secretions of A. dahurica var. formosana significantly increased, thereby promoting the ratio of C to N in rhizosphere and nonrhizosphere soils, increasing carbon sequestration, and shaping the microbial community composition, thus promoting a higher yield and furanocoumarin synthesis. Confirmation through the construction of a synthetic microbial community and feedback experiments indicated that beneficial plant growth-promoting rhizobacteria play a crucial role in improving nitrogen utilization efficiency and selectively regulating the synthesis of target furanocoumarins under low nitrogen conditions. These findings may contribute additional theoretical evidence for understanding the mechanisms of interaction between medicinal plants and rhizosphere microorganisms.

Fulvic Acid Promotes Legume-Rhizobium Symbiosis by Stimulating Endogenous Flavonoids Synthesis and Secretion

Fulvic acid (FA) promotes symbiosis between legumes and rhizobia. To elucidate from the aspect of symbiosis, the effects of root irrigation of water-soluble humic materials (WSHM) or foliar spraying of its highly active component, FA, on soybean root exudates and on rhizosphere microorganisms were investigated. As a result, WSHM/FA treatments significantly altered root exudate metabolite composition, and isoflavonoids were identified as key contributors in both treatments compared to the control. Increased expression of genes related to the isoflavonoid biosynthesis were validated by RT-qPCR in both treatments, which notably elevated the synthesis of symbiotic signals genistein, daidzin, coumestrol, and biochanin A. Moreover, the WSHM/FA treatments induced a change in rhizosphere microbial community, coupled with an increase in the relative abundance of rhizobia. Our findings showed that WSHM/FA promotes symbiosis by stimulating the endogenous flavonoid synthesis and leads to rhizobia accumulation in the rhizosphere. This study provides new insights into mechanisms underlying the FA-mediated promotion of symbiosis.

Chemodiversity of Arctic Plant Dryas oxyodonta: LC-MS Profile and Antioxidant Activity

Dryas oxyodonta Yuz. is a perennial evergreen shrub from the Rosaceae family. D. oxyodonta thrives in subalpine and subarctic regions, as well as in highlands spanning from Central Asia to Siberia and Mongolia. Owing to a lack of information on its chemical composition, we conducted qualitative and quantitative chromatographic analyses on extracts from the leaves and flowers of D. oxyodonta sourced from various Siberian habitats. Employing high-performance liquid chromatography with photodiode-array detection and electrospray ionization triple-quadrupole mass spectrometric detection, we identified 40 compounds, encompassing gallotannins, hydroxycinnamates, procyanidins, catechins, flavonoids, and triterpenes. All Siberian populations of D. oxyodonta exhibited a notable abundance of phenolic compounds. Furthermore, we identified rare glycosides, such as sexangularetin and corniculatusin, as potential markers of the chemodiversity within the Dryas genus. Extracts from the flowers and leaves were effective scavengers of free radicals, including DPPH•, ABTS•+-, O2•-, and •OH radicals. Our findings unequivocally establish D. oxyodonta as a rich source of phenolic compounds with potent antioxidant activity, suggesting its potential utility in developing novel functional products.

Soybean AROGENATE DEHYDRATASES (GmADTs): involvement in the cytosolic isoflavonoid metabolon or trans-organelle continuity?

Soybean (Glycine max) produces a class of phenylalanine (Phe) derived specialized metabolites, isoflavonoids. Isoflavonoids are unique to legumes and are involved in defense responses in planta, and they are also necessary for nodule formation with nitrogen-fixing bacteria. Since Phe is a precursor of isoflavonoids, it stands to reason that the synthesis of Phe is coordinated with isoflavonoid production. Two putative AROGENATE DEHYDRATASE (ADT) isoforms were previously co-purified with the soybean isoflavonoid metabolon anchor ISOFLAVONE SYNTHASE2 (GmIFS2), however the GmADT family had not been characterized. Here, we present the identification of the nine member GmADT family. We determined that the GmADTs share sequences required for enzymatic activity and allosteric regulation with other characterized plant ADTs. Furthermore, the GmADTs are differentially expressed, and multiple members have dual substrate specificity, also acting as PREPHENATE DEHYDRATASES. All GmADT isoforms were detected in the stromules of chloroplasts, and they all interact with GmIFS2 in the cytosol. In addition, GmADT12A interacts with multiple other isoflavonoid metabolon members. These data substantiate the involvement of GmADT isoforms in the isoflavonoid metabolon.

Comparative transcriptome analysis of two contrasting genotypes provides new insights into the drought response mechanism in pigeon pea (Cajanus cajan L. Millsp.)

BACKGROUND

Despite plant's ability to adapt and withstand challenging environments, drought poses a severe threat to their growth and development. Although pigeon pea is already quite resistant to drought, the prolonged dehydration induced by the aberrant climate poses a serious threat to their survival and productivity.

OBJECTIVE

Comparative physiological and transcriptome analyses of drought-tolerant (CO5) and drought-sensitive (CO1) pigeon pea genotypes subjected to drought stress were carried out in order to understand the molecular basis of drought tolerance in pigeon pea.

METHODS

The transcriptomic analysis allowed us to examine how drought affects the gene expression of C. cajan. Using bioinformatics tools, the unigenes were de novo assembled, annotated, and functionally evaluated. Additionally, a homology-based sequence search against the droughtDB database was performed to identify the orthologs of the DEGs.

RESULTS

1102 potential drought-responsive genes were found to be differentially expressed genes (DEGs) between drought-tolerant and drought-sensitive genotypes. These included Abscisic acid insensitive 5 (ABI5), Nuclear transcription factor Y subunit A-7 (NF-YA7), WD40 repeat-containing protein 55 (WDR55), Anthocyanidin reductase (ANR) and Zinc-finger homeodomain protein 6 (ZF-HD6) and were highly expressed in the tolerant genotype. Further, GO analysis revealed that the most enriched classes belonged to biosynthetic and metabolic processes in the biological process category, binding and catalytic activity in the molecular function category and nucleus and protein-containing complex in the cellular component category. Results of KEGG pathway analysis revealed that the DEGs were significantly abundant in signalling pathways such as plant hormone signal transduction and MAPK signalling pathways. Consequently, in our investigation, we have identified and validated by qPCR a group of genes involved in signal reception and propagation, stress-specific TFs, and basal regulatory genes associated with drought response.

CONCLUSION

In conclusion, our comprehensive transcriptome dataset enabled the discovery of candidate genes connected to pathways involved in pigeon pea drought response. Our research uncovered a number of unidentified genes and transcription factors that could be used to understand and improve susceptibility to drought.

Effects of Climate Conditions before Harvest Date on Edamame Metabolome

Edamame is a green soybean that is rich in nutrients. Boiled edamame has been traditionally used for food in the East Asia region. It was known among farmers that conditions, such as temperature and climate on the day of harvest, affect the quality of edamame. Large-scale farmers harvest edamame on multiple days in the same year; however, the quality of edamame varies from day to day due to variations in climate conditions. In this study, we harvested edamame over several days between 2013 and 2018, obtained the climate conditions on the harvest date, and performed metabolome analysis using capillary electrophoresis mass spectrometry. To clarify the correlation between climate conditions before the harvest date and edamame components, comparative analyses of the obtained meteorological and metabolomic data were conducted. We found positive and negative correlations between the sunshine duration and average temperature, and the amounts of some edamame components. Furthermore, correlations were observed between the annual fluctuations in climate conditions and edamame components. Our findings suggest that the climate conditions before the date of harvesting are closely related to edamame quality.

Mutation of MYB36 affects isoflavonoid metabolism, growth, and stress responses in Lotus japonicus

Isoflavonoids are mostly produced by legumes although little is known about why and how legumes are able to regulate the biosynthesis of these particular compounds. Understanding the role of potential regulatory genes of the isoflavonoid biosynthetic pathway constitutes an important topic of research. The LORE1 mutation of the gene encoding the transcription factor MYB36 allowed the identification of this gene as a regulator of isoflavonoid biosynthesis in Lotus japonicus plants. The levels of several isoflavonoid compounds were considerably lower in two lines of Ljmyb36 mutant plants compared to the WT. In addition, we found that Ljmyb36 mutant plants were significantly smaller and showed a substantial decrease in the chlorophyll levels under normal growth conditions. The analysis of plants subjected to different types of abiotic stress conditions further revealed that mutant plants presented a higher sensitivity than WT plants, indicating that the MYB36 transcription factor is also involved in the stress response in L. japonicus plants.

Photorespiration: regulation and new insights on the potential role of persulfidation

Photorespiration has been considered a 'futile' cycle in C3 plants, necessary to detoxify and recycle the metabolites generated by the oxygenating activity of Rubisco. However, several reports indicate that this metabolic route plays a fundamental role in plant metabolism and constitutes a very interesting research topic. Many open questions still remain with regard to photorespiration. One of these questions is how the photorespiratory process is regulated in plants and what factors contribute to this regulation. In this review, we summarize recent advances in the regulation of the photorespiratory pathway with a special focus on the transcriptional and post-translational regulation of photorespiration and the interconnections of this process with nitrogen and sulfur metabolism. Recent findings on sulfide signaling and protein persulfidation are also described.

Primary and Secondary Metabolites in Lotus japonicus

Lotus japonicus is a leguminous model plant used to gain insight into plant physiology, stress response, and especially symbiotic plant-microbe interactions, such as root nodule symbiosis or arbuscular mycorrhiza. Responses to changing environmental conditions, stress, microbes, or insect pests are generally accompanied by changes in primary and secondary metabolism to account for physiological needs or to produce defensive or signaling compounds. Here we provide an overview of the primary and secondary metabolites identified in L. japonicus to date. Identification of the metabolites is mainly based on mass spectral tags (MSTs) obtained by gas chromatography linked with tandem mass spectrometry (GC-MS/MS) or liquid chromatography-MS/MS (LC-MS/MS). These MSTs contain retention index and mass spectral information, which are compared to databases with MSTs of authentic standards. More than 600 metabolites are grouped into compound classes such as polyphenols, carbohydrates, organic acids and phosphates, lipids, amino acids, nitrogenous compounds, phytohormones, and additional defense compounds. Their physiological effects are briefly discussed, and the detection methods are explained. This review of the exisiting literature on L. japonicus metabolites provides a valuable basis for future metabolomics studies.

Hydroxy Chalcones and Analogs with Chemopreventive Properties

The aim of this review is to highlight the chemopreventive properties of hydroxy-substituted natural and synthetic chalcones along with a number of their analogs. These products display various biological activities, and have many applications against various diseases. Antioxidant and anti-inflammatory properties of chalcones bearing hydroxy substituents are underlined. The influence of hydroxy substituents located on ring A, B, or both are systematized according to the exhibited biological properties.

The R2R3-MYB-SG7 transcription factor CaMYB39 orchestrates surface phenylpropanoid metabolism and pathogen resistance in chickpea

Flavonoids are important plant pigments and defense compounds; understanding the transcriptional regulation of flavonoid biosynthesis may enable engineering crops with improved nutrition and stress tolerance. Here, we characterize R2R3-MYB domain subgroup 7 transcription factor CaMYB39, which regulates flavonol biosynthesis primarily in chickpea trichomes. CaMYB39 overexpression in chickpea was accompanied by a change in flux availability for the phenylpropanoid pathway, particularly flavonol biosynthesis. Lines overexpressing CaMYB39 showed higher isoflavonoid levels, suggesting its role in regulating isoflavonoid pathway. CaMYB39 transactivates the transcription of early flavonoid biosynthetic genes (EBG). FLAVONOL SYNTHASE2, an EBG, encodes an enzyme with higher substrate specificity for dihydrokaempferol than other dihydroflavonols explaining the preferential accumulation of kaempferol derivatives as prominent flavonols in chickpea. Interestingly, CaMYB39 overexpression increased trichome density and enhanced the accumulation of diverse flavonol derivatives in trichome-rich tissues. Moreover, CaMYB39 overexpression reduced reactive oxygen species levels and induced defense gene expression which aids in partially blocking the penetration efficiency of the fungal pathogen, Ascochyta rabiei, resulting in lesser symptoms, thus establishing its role against deadly Ascochyta blight (AB) disease. Overall, our study reports an instance where R2R3-MYB-SG7 member, CaMYB39, besides regulating flavonol biosynthesis, modulates diverse pathways like general phenylpropanoid, isoflavonoid, trichome density, and defense against necrotrophic fungal infection in chickpea.

UV-B radiation enhances isoflavone accumulation and antioxidant capacity of soybean calluses

Isoflavones are a class of flavonoids that belong to a large family of polyphenols and synthesized predominantly in legume, and they play important roles including acting as antioxidant, preventing osteoporosis, reducing the risk of atherosclerosis, and protecting against cardiovascular disease. This study focused on the accumulation and synthetic metabolism of isoflavone in soybean hypocotyl and cotyledon calluses under UV-B radiation. The results showed that UV-B radiation significantly up-regulated the gene expression of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumarate-CoA ligase (4CL), chalcone ketone synthase (CHS), chalcone isomerase (CHI), and isoflavone synthase (IFS), and enhanced their activity in soybean hypocotyl and cotyledon calluses. As a result, isoflavones content increased by 21.23 and 21.75% in soybean hypocotyl and cotyledon calluses, respectively. Among the isoflavones produced, malonyldaidzin was the dominant one in hypocotyl callus, while malonylglycitin and daidzein were the main isoflavones in cotyledon calluses. This study revealed that UV-B radiation induced isoflavone accumulation in soybean calluses, which could be an efficient strategy to improve the nutritional value of food and produce high levels of bioactive secondary metabolites.

Spatiotemporal transcriptomics and metabolic profiling provide insights into gene regulatory networks during lentil seed development

Lentil (Lens culinaris Medik.) is a nutritious legume with seeds rich in protein, minerals and an array of diverse specialized metabolites. The formation of a seed requires regulation and tight coordination of developmental programs to form the embryo, endosperm and seed coat compartments, which determines the structure and composition of mature seed and thus its end-use quality. Understanding the molecular and cellular events and metabolic processes of seed development is essential for improving lentil yield and seed nutritional value. However, such information remains largely unknown, especially at the seed compartment level. In this study, we generated high-resolution spatiotemporal gene expression profiles in lentil embryo, seed coat and whole seeds from fertilization through maturation. Apart from anatomic differences between the embryo and seed coat, comparative transcriptomics and weighted gene co-expression network analysis revealed embryo- and seed coat-specific genes and gene modules predominant in specific tissues and stages, which highlights distinct genetic programming. Furthermore, we investigated the dynamic profiles of flavonoid, isoflavone, phytic acid and saponin in seed compartments across seed development. Coupled with transcriptome data, we identified sets of candidate genes involved in the biosynthesis of these metabolites. The global view of the transcriptional and metabolic changes of lentil seed tissues throughout development provides a valuable resource for dissecting the genetic control of secondary metabolism and development of molecular tools for improving seed nutritional quality.

Transcriptome and Metabolome Profiling Provide Insights into Flavonoid Synthesis in Acanthus ilicifolius Linn

Acanthus ilicifolius is an important medicinal plant in mangrove forests, which is rich in secondary metabolites with various biological activities. In this study, we used transcriptomic analysis to obtain differentially expressed genes in the flavonoid metabolic pathway and metabolomic methods to detect changes in the types and content in the flavonoid metabolic synthesis pathway. The results showed that DEGs were identified in the mature roots vs. leaves comparison (9001 up-regulated and 8910 down-regulated), mature roots vs. stems comparison (5861 up-regulated and 7374 down-regulated), and mature stems vs. leaves comparison (10,837 up-regulated and 11,903 down-regulated). Furthermore, two AiCHS genes and four AiCHI genes were up-regulated in the mature roots vs. stems of mature A. ilicifolius, and were down-regulated in mature stems vs. leaves, which were highly expressed in the A. ilicifolius stems. A total of 215 differential metabolites were found in the roots vs. leaves of mature A. ilicifolius, 173 differential metabolites in the roots vs. stems, and 228 differential metabolites in the stems vs. leaves. The metabolomic results showed that some flavonoids in A. ilicifolius stems were higher than in the roots. A total of 18 flavonoid differential metabolites were detected in the roots, stems, and leaves of mature A. ilicifolius. In mature leaves, quercetin-3-O-glucoside-7-O-rhamnoside, gossypitrin, isoquercitrin, quercetin 3,7-bis-O-β-D-glucoside, and isorhamnetin 3-O-β-(2″-O-acetyl-β-D-glucuronide) were found in a high content, while in mature roots, di-O-methylquercetin and isorhamnetin were the major compounds. The combined analysis of the metabolome and transcriptome revealed that DEGs and differential metabolites were related to flavonoid biosynthesis. This study provides a theoretical basis for analyzing the molecular mechanism of flavonoid synthesis in A. ilicifolius and provides a reference for further research and exploitation of its medicinal value.

Effect of Biotic Elicitors on the Growth, Antioxidant Activity and Metabolites Accumulation in In Vitro Propagated Shoots of Pueraria tuberosa

Pueraria tuberosa contains a wide range of bioactive compounds, including polyphenols, alkaloids, and phytosterols, which make it valuable to the pharmaceutical and food industries. Elicitor compounds trigger the defense mechanisms in plants and are widely used to increase the yield of bioactive molecules in in vitro cultures. The present study was conducted to evaluate the effects of different concentrations of biotic elicitors such as yeast extract (YE), pectin (PEC), and alginate (ALG) on growth, antioxidant activity, and metabolite accumulation in in vitro propagated shoots of P. tuberosa. The elicitors applied to shoot cultures of P. tuberosa significantly increased biomass (shoot number, fresh weight, and dry weight), and metabolites such as protein, carbohydrates, chlorophyll, total phenol (TP), and total flavonoid (TF) contents, as well as antioxidant activity compared to untreated control. Biomass, TP, and TF contents, as well as antioxidant activity, were most significant in cultures treated with 100 mg/L PEC. In contrast, chlorophyll, protein, and carbohydrate increased most in cultures treated with 200 mg/L ALG. Application of 100 mg/L of PEC led to the accumulation of high amounts of isoflavonoids including puerarin (220.69 μg/g), daidzin (2935.55 μg/g), genistin (5612 μg/g), daidzein (479.81 μg/g), and biochanin-A (111.511 μg/g) as analyzed by high-performance liquid chromatography (HPLC). Total isoflavonoids content of 100 mg/L PEC treated shoots was obtained as 9359.56 μg/g, 1.68-fold higher than in vitro propagated shoots without elicitors (5573.13 μg/g) and 2.77-fold higher than shoots of the mother plant (3380.17 μg/g). The elicitor concentrations were optimized as 200 mg/L YE, 100 mg/L PEC, and 200 mg/L ALG. Overall, this study showed that the application of different biotic elicitors resulted in better growth, antioxidant activity, and accumulation of metabolites in P. tuberosa, which could lead to obtaining phytopharmaceutical advantages in the future.

Investigating the antioxidant activity enhancer effect of Cyamopsis tetragonoloba seed extract on phenolic phytochemicals

INTRODUCTION

Phenolic phytochemicals are known for antioxidant-mediated pharmacological effects in various diseases (diabetes, cancer, CVDs, obesity, inflammatory and neurodegenerative disorders). However, individual compounds may not exert the same biological potency as in combination with other phytochemicals. Cyamopsis tetragonoloba (Guar), an underutilized semi-arid legume which has been used as a traditional food in Rajasthan (India), is also a source of the important industrial product guar gum. However, studies on its biological activity, like antioxidant, are limited.

METHODS

We tested the effect of C. tetragonoloba seed extract to enhance the antioxidant activity of well-known dietary flavonoids (quercetin, kaempferol, luteolin, myricetin, and catechin) and non-flavonoid phenolics (caffeic acid, ellagic acid, taxifolin, epigallocatechin gallate (EGCG), and chlorogenic acid) using DPPH radical scavenging assay. The most synergistic combination was further validated for its cytoprotective and anti-lipid peroxidative effects in in vitro cell culture system, at different concentrations of the extract. LC-MS analysis of purified guar extract was also performed.

RESULTS AND DISCUSSION

In most cases, we observed synergy at lower concentrations of the seed extract (0.5-1 mg/ml). The extract concentration of 0.5 mg/ml enhanced the antioxidant activity of Epigallocatechin gallate (20 µg/ml) by 2.07-folds, implicating its potential to act as an antioxidant activity enhancer. This synergistic seed extract-EGCG combination diminished the oxidative stress nearly by double-fold when compared with individual phytochemical treatments in in vitro cell culture. LC-MS analysis of the purified guar extract revealed some previously unreported metabolites, including catechin hydrate, myricetin-3-galactoside, gossypetin-8-glucoside, and puerarin (daidzein-8-C-glucoside) which possibly explains its antioxidant enhancer effect. The outcomes of this study could be used for development of effective nutraceutical/dietary supplements.

Red and blue light-specific metabolic changes in soybean seedlings

Red and blue artificial light sources are commonly used as photosynthetic lighting in smart farm facilities, and they can affect the metabolisms of various primary and secondary metabolites. Although the soybean plant contains major flavonoids such as isoflavone and flavonol, using light factors to produce specific flavonoids from this plant remains difficult because the regulation of light-responded flavonoids is poorly understood. In this study, metabolic profiling of soybean seedlings in response to red and blue lights was evaluated, and the isoflavone-flavonol regulatory mechanism under different light irradiation periods was elucidated. Profiling of metabolites, including flavonoids, phenolic acids, amino acids, organic acids, free sugars, alcohol sugars, and sugar acids, revealed that specific flavonol, isoflavone, and phenolic acid showed irradiation time-dependent accumulation. Therefore, the metabolic gene expression level and accumulation of isoflavone and flavonol were further investigated. The light irradiation period regulated kaempferol glycoside, the predominant flavonol in soybeans, with longer light irradiation resulting in higher kaempferol glycoside content, regardless of photosynthetic lights. Notably, blue light stimulated kaempferol-3-O-(2,6-dirhamnosyl)-galactoside accumulation more than red light. Meanwhile, isoflavones were controlled differently based on isoflavone types. Malonyl daidzin and malonyl genistin, the predominant isoflavones in soybeans, were significantly increased by short-term red light irradiation (12 and 36 h) with higher expressions of flavonoid biosynthetic genes, which contributed to the increased total isoflavone level. Although most isoflavones increased in response to red and blue lights, daidzein increased in response only to red light. In addition, prolonged red light irradiation downregulated the accumulation of glycitin types, suggesting that isoflavone's structural specificity results in different accumulation in response to light. Overall, these findings suggest that the application of specific wavelength and irradiation periods of light factors enables the regulation and acquisition of specialized metabolites from soybean seedlings.

Low nitrogen stress-induced transcriptome changes revealed the molecular response and tolerance characteristics in maintaining the C/N balance of sugar beet (Beta vulgaris L.)

Nitrogen (N) is an essential macronutrient for plants, acting as a common limiting factor for crop yield. The application of nitrogen fertilizer is related to the sustainable development of both crops and the environment. To further explore the molecular response of sugar beet under low nitrogen (LN) supply, transcriptome analysis was performed on the LN-tolerant germplasm '780016B/12 superior'. In total, 580 differentially expressed genes (DEGs) were identified in leaves, and 1,075 DEGs were identified in roots (log₂ ^|FC| ≥ 1; q value < 0.05). Gene Ontology (GO), protein-protein interaction (PPI), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses clarified the role and relationship of DEGs under LN stress. Most of the downregulated DEGs were closely related to "photosynthesis" and the metabolism of "photosynthesis-antenna proteins", "carbon", "nitrogen", and "glutathione", while the upregulated DEGs were involved in flavonoid and phenylalanine biosynthesis. For example, GLUDB (glutamate dehydrogenase B) was identified as a key downregulated gene, linking carbon, nitrogen, and glutamate metabolism. Thus, low nitrogen-tolerant sugar beet reduced energy expenditure mainly by reducing the synthesis of energy-consuming amino acids, which in turn improved tolerance to low nitrogen stress. The glutathione metabolism biosynthesis pathway was promoted to quench reactive oxygen species (ROS) and protect cells from oxidative damage. The expression levels of nitrogen assimilation and amino acid transport genes, such as NRT2.5 (high-affinity nitrate transporter), NR (nitrate reductase [NADH]), NIR (ferredoxin-nitrite reductase), GS (glutamine synthetase leaf isozyme), GLUDB, GST (glutathione transferase) and GGT3 (glutathione hydrolase 3) at low nitrogen levels play a decisive role in nitrogen utilization and may affect the conversion of the carbon skeleton. DFRA (dihydroflavonol 4-reductase) in roots was negatively correlated with NIR in leaves (coefficient = -0.98, p < 0.05), suggesting that there may be corresponding remote regulation between "flavonoid biosynthesis" and "nitrogen metabolism" in roots and leaves. FBP (fructose 1,6-bisphosphatase) and PGK (phosphoglycerate kinase) were significantly positively correlated (p < 0.001) with Ci (intercellular CO₂ concentration). The reliability and reproducibility of the RNA-seq data were further confirmed by real-time fluorescence quantitative PCR (qRT-PCR) validation of 22 genes (R² = 0.98). This study reveals possible pivotal genes and metabolic pathways for sugar beet adaptation to nitrogen-deficient environments.

Integration of transcriptomic and metabolomic analyses provides insights into response mechanisms to nitrogen and phosphorus deficiencies in soybean

Nitrogen (N) and phosphorus (P) are two essential plant macronutrients that can limit plant growth by different mechanisms. We aimed to shed light on how soybean respond to low nitrogen (LN), low phosphorus (LP) and their combined deficiency (LNP). Generally, these conditions triggered changes in gene expression of the same processes, including cell wall organization, defense response, response to oxidative stress, and photosynthesis, however, response was different in each condition. A typical primary response to LN and LP was detected also in soybean, i.e., the enhanced uptake of N and P, respectively, by upregulation of genes for the corresponding transporters. The regulation of genes involved in cell wall organization showed that in LP roots tended to produce more casparian strip, in LN more secondary wall biosynthesis occurred, and in LNP reduction in expression of genes involved in secondary wall production accompanied by cell wall loosening was observed. Flavonoid biosynthesis also showed distinct pattern of regulation in different conditions: more anthocyanin production in LP, and more isoflavonoid production in LN and LNP, which we confirmed also on the metabolite level. Interestingly, in soybean the nutrient deficiencies reduced defense response by lowering expression of genes involved in defense response, suggesting a role of N and P nutrition in plant disease resistance. In conclusion, we provide detailed information on how LN, LP, and LNP affect different processes in soybean roots on the molecular and physiological levels.

Current perspectives on the beneficial effects of soybean isoflavones and their metabolites on plants

Soybeans have traditionally been a staple part of the human diet being highly rich in protein and lipid content. In an addition to the high nutritional components, soybeans have several functional components, like isoflavones, saponins, lecithin, and oligosaccharides. Soybeans emerge as a healthy functional food option. Isoflavones are most notable functional component of soybeans, exhibiting antioxidant activity while preventing plant-related diseases (e.g., antimicrobial and antiherbivore activities) and having positive effects on the life quality of plants. Isoflavones are thus sometimes referred to as phytochemicals. The latest research trends evince substantial interest in the biological efficacy of isoflavones in the human body as well as in plants and their related mechanisms. However, there is little information on the relationship between isoflavones and plants than beneficial human effects. This review discusses what is known about the physiological communication (transport and secretion) between isoflavones and plants, especially in soybeans.

Chalcone Scaffolds, Bioprecursors of Flavonoids: Chemistry, Bioactivities, and Pharmacokinetics

Chalcones are secondary metabolites belonging to the flavonoid (C6-C3-C6 system) family that are ubiquitous in edible and medicinal plants, and they are bioprecursors of plant flavonoids. Chalcones and their natural derivatives are important intermediates of the flavonoid biosynthetic pathway. Plants containing chalcones have been used in traditional medicines since antiquity. Chalcones are basically α,β-unsaturated ketones that exert great diversity in pharmacological activities such as antioxidant, anticancer, antimicrobial, antiviral, antitubercular, antiplasmodial, antileishmanial, immunosuppressive, anti-inflammatory, and so on. This review provides an insight into the chemistry, biosynthesis, and occurrence of chalcones from natural sources, particularly dietary and medicinal plants. Furthermore, the pharmacological, pharmacokinetics, and toxicological aspects of naturally occurring chalcone derivatives are also discussed herein. In view of having tremendous pharmacological potential, chalcone scaffolds/chalcone derivatives and bioflavonoids after subtle chemical modification could serve as a reliable platform for natural products-based drug discovery toward promising drug lead molecules/drug candidates.

Production of Genistein in Amaranthus tricolor var. tristis and Spinacia oleracea by Expression of Glycine max Isoflavone Synthase

Isoflavonoids, the diverse group of secondary metabolites derived from the phenylpropanoid pathway, are distributed predominantly in leguminous plants. It has received considerable attention in recent days due to its health promoting benefits and is known to prevent certain diseases in humans. These isoflavonoids are synthesized from flavonoid intermediates of phenylpropanoid pathway by the enzyme isoflavone synthase. Metabolic engineering of isoflavonoid biosynthesis in non-legume crop plants could offer the health benefits of these compounds in diverse plant species further contributing for crop improvement. The transient expression of heterologous genes in the host is considered as an alternative to stable expression, that can provide a rapid way of studying the pathway engineering for metabolite production and could also act as a production platform for nutraceuticals and biopharmaceuticals. In this study, isoflavone genistein was produced in Amaranthus tricolor var. tristis and Spinacia oleracea by transiently expressing Glycine max isoflavone synthase (GmIFS). The GmIFS gene was cloned in plant expression vector pEarleyGate 102 HA and pEAQ-HT-DEST 3 and transformed into plants by agroinfiltration. The presence of transgene in the agroinfiltrated leaves was confirmed by semiquantitative reverse-transcription polymerase chain reaction. The flavonoid substrate naringenin and isoflavonoid genistein were quantified using high performance liquid chromatography in both wild-type and infiltrated leaf samples of both the plants. The naringenin content varied in the range of 65.5-338.5 nM/g fresh weight, while the accumulation of genistein was observed with varying concentrations from 113 to 182.6 nM/g fresh weight in the agroinfiltrated leaf samples of both A. tricolor var. tristis and S. oleracea. These results indicate that the transient expression of GmIFS gene has led to the synthesis of isoflavonoid genistein in A. tricolor var. tristis and S. oleracea providing an insight that stable expression of this gene could enrich the nutraceutical content in the crop plants. To the best of our knowledge, this is the first report on transient expression of GmIFS gene for the production of genistein in A. tricolor var. tristis and S. oleracea.

Characterization and Comparison of Bacterial Communities of an Invasive and Two Native Caribbean Seagrass Species Sheds Light on the Possible Influence of the Microbiome on Invasive Mechanisms

Invasive plants, including marine macrophytes, are one of the most important threats to biodiversity by displacing native species and organisms depending on them. Invasion success is dependent on interactions among living organisms, but their study has been mostly limited to negative interactions while positive interactions are mostly underlooked. Recent studies suggested that microorganisms associated with eukaryotic hosts may play a determinant role in the invasion process. Along with the knowledge of their structure, taxonomic composition, and potential functional profile, understanding how bacterial communities are associated with the invasive species and the threatened natives (species-specific/environmentally shaped/tissue-specific) can give us a holistic insight into the invasion mechanisms. Here, we aimed to compare the bacterial communities associated with leaves and roots of two native Caribbean seagrasses (Halodule wrightii and Thalassia testudinum) with those of the successful invader Halophila stipulacea, in the Caribbean island Curaçao, using 16S rRNA gene amplicon sequencing and functional prediction. Invasive seagrass microbiomes were more diverse and included three times more species-specific core OTUs than the natives. Associated bacterial communities were seagrass-specific, with higher similarities between natives than between invasive and native seagrasses for both communities associated with leaves and roots, despite their strong tissue differentiation. However, with a higher number of OTUs in common, the core community (i.e., OTUs occurring in at least 80% of the samples) of the native H. wrightii was more similar to that of the invader H. stipulacea than T. testudinum, which could reflect more similar essential needs (e.g., nutritional, adaptive, and physiological) between native and invasive, in contrast to the two natives that might share more environment-related OTUs. Relative to native seagrass species, the invasive H. stipulacea was enriched in halotolerant bacterial genera with plant growth-promoting properties (like Halomonas sp. and Lysinibacillus sp.) and other potential beneficial effects for hosts (e.g., heavy metal detoxifiers and quorum sensing inhibitors). Predicted functional profiles also revealed some advantageous traits on the invasive species such as detoxification pathways, protection against pathogens, and stress tolerance. Despite the predictive nature of our findings concerning the functional potential of the bacteria, this investigation provides novel and important insights into native vs. invasive seagrasses microbiome. We demonstrated that the bacterial community associated with the invasive seagrass H. stipulacea is different from native seagrasses, including some potentially beneficial bacteria, suggesting the importance of considering the microbiome dynamics as a possible and important influencing factor in the colonization of non-indigenous species. We suggest further comparison of H. stipulacea microbiome from its native range with that from both the Mediterranean and Caribbean habitats where this species has a contrasting invasion success. Also, our new findings open doors to a more in-depth investigation combining meta-omics with bacterial manipulation experiments in order to confirm any functional advantage in the microbiome of this invasive seagrass.

Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans

Soybeans are rich in proteins and lipids and have become a staple part of the human diet. Besides their nutritional excellence, they have also been shown to contain various functional components, including isoflavones, and have consequently received increasing attention as a functional food item. Isoflavones are structurally similar to 17-β-estradiol and bind to estrogen receptors (ERα and ERβ). The estrogenic activity of isoflavones ranges from a hundredth to a thousandth of that of estrogen itself. Isoflavones play a role in regulating the effects of estrogen in the human body, depending on the situation. Thus, when estrogen is insufficient, isoflavones perform the functions of estrogen, and when estrogen is excessive, isoflavones block the estrogen receptors to which estrogen binds, thus acting as an estrogen antagonist. In particular, estrogen antagonistic activity is important in the breast, endometrium, and prostate, and such antagonistic activity suppresses cancer occurrence. Genistein, an isoflavone, has cancer-suppressing effects on estrogen receptor-positive (ER+) cancers, including breast cancer. It suppresses the function of enzymes such as tyrosine protein kinase, mitogen-activated kinase, and DNA polymerase II, thus inhibiting cell proliferation and inducing apoptosis. Genistein is the most biologically active and potent isoflavone candidate for cancer prevention. Furthermore, among the various physiological functions of isoflavones, they are best known for their antioxidant activities. S-Equol, a metabolite of genistein and daidzein, has strong antioxidative effects; however, the ability to metabolize daidzein into S-equol varies based on racial and individual differences. The antioxidant activity of isoflavones may be effective in preventing dementia by inhibiting the phosphorylation of Alzheimer's-related tau proteins. Genistein also reduces allergic responses by limiting the expression of mast cell IgE receptors, which are involved in allergic responses. In addition, they have been known to prevent and treat various diseases, including cardiovascular diseases, metabolic syndromes, osteoporosis, diabetes, brain-related diseases, high blood pressure, hyperlipidemia, obesity, and inflammation. Further, it also has positive effects on menstrual irregularity in non-menopausal women and relieving menopausal symptoms in middle-aged women. Recently, soybean consumption has shown steep increasing trend in Western countries where the intake was previously only 1/20-1/50 of that in Asian countries. In this review, I have dealt with the latest research trends that have shown substantial interest in the biological efficacy of isoflavones in humans and plants, and their related mechanisms.

Special Issue Editorial: Plant Nitrogen Assimilation and Metabolism

Nitrogen is an important macronutrient for plant growth and development. Research has long been carried out to elucidate the mechanisms involved in nitrogen uptake, assimilation, and utilization in plants. However, despite recent advances, many of these mechanisms still are not fully understood. In this special issue, several research articles and two reviews, all of them aiming to elucidate some specific aspects of nitrogen (N) metabolism, are presented. Together, the articles in this issue provide a state-of-the-art perspective on important questions related to nitrogen metabolism in photosynthetic organisms, highlighting the fundamental importance of research in this field.

Pleiotropic Effects of Isoflavones in Inflammation and Chronic Degenerative Diseases

Isoflavones are phytoestrogens of plant origin, mostly found in the members of the Fabaceae family, that exert beneficial effects in various degenerative disorders. Having high similarity to 17-β-estradiol, isoflavones can bind estrogen receptors, scavenge reactive oxygen species, activate various cellular signal transduction pathways and modulate growth and transcription factors, activities of enzymes, cytokines, and genes regulating cell proliferation and apoptosis. Due to their pleiotropic activities isoflavones might be considered as a natural alternative for the treatment of estrogen decrease-related conditions during menopause. This review will focus on the effects of isoflavones on inflammation and chronic degenerative diseases including cancer, metabolic, cardiovascular, neurodegenerative diseases, rheumatoid arthritis and adverse postmenopausal symptoms.

Nutritional component changes in Xiangfen 1 banana at different developmental stages

Banana is an essential food resource in many tropical and subtropical countries. Metabolites in banana greatly influence its nutritional value and flavor. However, metabolic changes that occur in different developmental stages have not been comprehensively evaluated. In this study, widely targeted metabolomics based on multiple reaction monitoring was used in investigating dynamic changes in metabolites at three stages of fruit development. A total of 655 metabolites were identified in all the stages. A hierarchical cluster analysis of metabolites showed six clear expression patterns at the three developmental stages, and 69 up-regulated differential metabolites were identified in mature fruits compared with young and mature green fruits. A metabolic pathway analysis of differential metabolites showed significant enrichment of the flavonoid biosynthesis pathway and the phenylalanine, tyrosine, and tryptophan biosynthesis pathways. These results may serve as a reference for the isolation and identification of functional compounds from banana and for their sufficient utilization in the future.