Ethylene Induced a High Accumulation of Dietary Isoflavones and Expression of Isoflavonoid Biosynthetic Genes in Soybean (Glycine max) Leaves

Chemical Compositions before and after Lactic Acid Fermentation of Isoflavone-Enriched Soybean Leaves and Their Anti-Obesity and Gut Microbiota Distribution Effects

In this study, we prepared fermented products of isoflavone-enriched soybean leaves (IESLs) and analyzed their nutrients, isoflavones, anti-obesity efficacy, and effects on gut microbiota. Fermented IESLs (FIESLs) were found to be rich in nutrients, especially lauric acid, oleic acid, and linoleic acid. In addition, the concentrations of most essential free amino acids were increased compared to those of IESLs. The contents of bioactive compounds, such as total phenolic, total flavonoid, daidzein, and genistein, significantly increased as well. In addition, FIESLs administration in a high-fat diet (HFD) animal model improved the final body weight, epididymal fat, total lipid, triglyceride, total cholesterol, blood glucose, and leptin levels, as well as reverting microbiota dysbiosis. In conclusion, these findings indicate that FIESLs have the potential to inhibit obesity caused by HFDs and serve as a modulator of gut microbiota, offering the prevention of diet-induced gut dysbiosis and metabolite diseases associated with obesity.

Recent advances in understanding the regulation of plant secondary metabolite biosynthesis by ethylene-mediated pathways

Plants produce a large repertoire of secondary metabolites. The pathways that lead to the biosynthesis of these metabolites are majorly conserved in the plant kingdom. However, a significant portion of these metabolites are specific to certain groups or species due to variations in the downstream pathways and evolution of the enzymes. These metabolites show spatiotemporal variation in their accumulation and are of great importance to plants due to their role in development, stress response and survival. A large number of these metabolites are in huge industrial demand due to their potential use as therapeutics, aromatics and more. Ethylene, as a plant hormone is long known, and its biosynthetic process, signaling mechanism and effects on development and response pathways have been characterized in many plants. Through exogenous treatments, ethylene and its inhibitors have been used to manipulate the production of various secondary metabolites. However, the research done on a limited number of plants in the last few years has only started to uncover the mechanisms through which ethylene regulates the accumulation of these metabolites. Often in association with other hormones, ethylene participates in fine-tuning the biosynthesis of the secondary metabolites, and brings specificity in the regulation depending on the plant, organ, tissue type and the prevailing conditions. This review summarizes the related studies, interprets the outcomes, and identifies the gaps that will help to breed better varieties of the related crops and produce high-value secondary metabolites for human benefits.

Isoflavone-enriched soybean leaves (Glycine max) restore loss of dermal collagen fibers induced by ovariectomy in the Sprague Dawley rats

Phytoestrogens, such as isoflavones, are known for their capacity to simulate various physiological impacts of estrogen in the human body. Our research evaluated the effects of isoflavone-enriched soybean leaves (IESL) on collagen fiber loss prompted by ovariectomy in Sprague Dawley (SD) rats, thereby simulating menopausal changes in women. IESL, bolstered with an increased concentration of isoflavones through a metabolite farming process, contained a significantly higher amount of isoflavones than regular soybean leaves. Our results indicate that the administration of IESL can counteract the decrease in relative optical density and dermal thickness of collagen fibers caused by ovariectomy in SD rats, with more pronounced effects observed at higher isoflavone dosages. These outcomes suggest that soybean leaves rich in isoflavones may hold potential benefits in combating collagen degradation and skin aging symptoms related to menopause. Further research is needed to fully understand the exact molecular pathways at play and the potential clinical relevance of these findings.

Ethylene enhances transcriptions of asparagine biosynthetic genes in soybean (Glycine max L. Merr) leaves

Soybean, a vital protein-rich crop, offers bioactivity that can mitigate various chronic human diseases. Nonetheless, soybean breeding poses a challenge due to the negative correlation between enhanced protein levels and overall productivity. Our previous studies demonstrated that applying gaseous phytohormone, ethylene, to soybean leaves significantly boosts the accumulation of free amino acids, particularly asparagine (Asn). Current studies also revealed that ethylene application to soybeans significantly enhanced both essential and non-essential amino acid contents in leaves and stems. Asn plays a crucial role in ammonia detoxification and reducing fatigue. However, the molecular evidence supporting this phenomenon remains elusive. This study explores the molecular mechanisms behind enhanced Asn accumulation in ethylene-treated soybean leaves. Transcriptional analysis revealed that ethylene treatments to soybean leaves enhance the transcriptional levels of key genes involved in Asn biosynthesis, such as aspartate aminotransferase (AspAT) and Asn synthetase (ASN), which aligns with our previous observations of elevated Asn levels. These findings shed light on the role of ethylene in upregulating Asn biosynthetic genes, subsequently enhancing Asn concentrations. This molecular insight into amino acid metabolism regulation provides valuable knowledge for the metabolic farming of crops, especially in elevating nutraceutical ingredients with non-genetic modification (GM) approach for improved protein content.

Changes in Nutrient Components and Digestive Enzymatic Inhibition Activities in Soy Leaves by Ethephon Treatment

In this study, the high isoflavone-enriched soy leaves (IESLs) were manufactured by treating with the chemical inducer ethephon, a plant growth regulator, to confirm changes in the properties of soy leaves (SLs), which are underutilized. Ethephon treatment concentrations consisted of 0 (SL1), 150 (SL2), and 300 (SL3) μg/mL. The composition analysis and physiological activity were conducted according to the ethephon treatment concentration of SLs. There was no significant difference in the proximate composition and fatty acids, except for an increase with increasing ethephon treatment concentrations. Depending on the ethephon treatment concentration, free amino acids increased to 1413.0, 1569.8, and 2100.4 mg/100 g, and water-soluble vitamins increased to 246.7, 244.7, and 501.6 mg/100 g. In particular, the functional substance isoflavone increased significantly to 1430.11, 7806.42, and 14,968.00 μg/g. Through this study, it was confirmed that the nutritional components and isoflavones of SLs increased according to the ethephon treatment concentration, a chemical inducer treatment agent. This can be used as a high-value-added biosubstance for raw materials for functional foods, cosmetics, and for natural drugs.

Ethephon promotes isoflavone accumulation in germinating soybeans by its acceleration of isoflavone biosynthetic pathway

Soybeans have medicinal value and are an oil crop with medicinal and food properties. The present work investigated two aspects of isoflavone accumulation in soybean. First, germination conditions for exogenous-ethephon-mediated accumulation of isoflavone were optimised through response surface methodology. Second, various influences of ethephon on the growth of germinating soybeans and isoflavone metabolism were investigated. The findings of the research led to the conclusion that exogenous ethephon treatment effectively facilitated the enrichment of isoflavones in soybeans during germination. Optimal germination conditions were obtained through a response surface optimization test, which yielded the following criteria: a germination time of 4.2 d, an ethephon concentration of 102.6 μM, and a germination temperature of 30.2 °C. The maximum isoflavone content was 544.53 μg/sprout FW. Relative to the control, the addition of ethephon significantly inhibited sprout growth. Exogenous ethephon treatment led to the phenomenon that peroxidase, superoxide dismutase, and catalase activities and their gene expression increased significantly in germinating soybeans. Meanwhile, the expression of genes related to ethylene synthetase increase under the effect of ethephon promoting ethylene synthesis. Ethylene multiplied the total flavonoid content of soybean sprouts relying on the increase in activity and gene expression of crucial isoflavone biosynthesis-related enzymes (phenylalanine ammonia-lyase and 4-coumarate coenzyme A ligase) during germination.

Potent Xanthine Oxidase Inhibitory Activity of Constituents of Agastache rugosa (Fisch. and C.A.Mey.) Kuntze

The aerial parts of Agastache rugosa are used as a food material and traditional medicine in Asia. A 50% ethanol extract exhibited potent xanthine oxidase (XO) inhibitory activity (IC₅₀ = 32.4 µg/mL). To investigate the major components responsible for this effect, seven known compounds were identified from A. rugosa; among these, salvianolic acid B (2) was isolated from this plant for the first time. Moreover, acacetin (7) exhibited the most potent inhibitory activity with an IC₅₀ value of 0.58 µM, lower than that of allopurinol (IC₅₀ = 4.2 µM), which is commonly used as a XO inhibitor. Comparative activity screening revealed that the C6-bonded monosaccharides (3) or sugars substituted with acetyl or malonyl groups (4-6) are critical for XO inhibition when converted to aglycone (7). The most potent inhibitor (7) in the A. rugosa extract (ARE) exhibited mixed-type inhibition kinetics and reversible inhibition toward XO. Furthermore, the hydrolysis of ARE almost converted to an inhibitor (7), which displayed the highest efficacy; UPLC-qTof MS revealed an increased content, up to five times more compared with that before treatment. This study will contribute to the enhancement in the industrial value of ARE hydrolysates as a functional ingredient and natural drug toward the management of hyperuricemia and treatment of gout.

Isoflavone-Enriched Soybean Leaves (Glycine Max) Alleviate Cognitive Impairment Induced by Ovariectomy and Modulate PI3K/Akt Signaling in the Hippocampus of C57BL6 Mice

(1) Background: The estrogen decline during perimenopause can induce various disorders, including cognitive impairment. Phytoestrogens, such as isoflavones, lignans, and coumestans, have been tried as a popular alternative to avoid the side effects of conventional hormone replacement therapy, but their exact mechanisms and risk are not fully elucidated. In this study, we investigated the effects of isoflavone-enriched soybean leaves (IESLs) on the cognitive impairment induced by ovariectomy in female mice. (2) Methods: Ovariectomy was performed at 9 weeks of age to mimic menopausal women, and the behavior tests for cognition were conducted 15 weeks after the first administration. IESLs were administered for 18 weeks. (3) Results: The present study showed the effects of IESLs on the cognitive function in the OVX (ovariectomized) mice. Ovariectomy markedly increased the body weight and fat accumulation in the liver and perirenal fat, but IESL treatment significantly inhibited them. In the behavioral tests, ovariectomy impaired cognitive functions, but administration of IESLs restored it. In addition, in the OVX mice, administration of IESLs restored decreased estrogen receptor (ER) β and PI3K/Akt expression in the hippocampus. (4) Conclusions: The positive effects of IESLs on cognitive functions may be closely related to the ER-mediated PI3/Akt signaling pathway in the hippocampus.

Comprehensive characterization of flavonoid derivatives in young leaves of core-collected soybean (Glycine max L.) cultivars based on high-resolution mass spectrometry

Most previous studies have been focused on isoflavone profile with biological activities from soybean seed and its related products. However, in the present study, eighty-three flavonoid derivatives (55 flavonols, 9 flavones and 19 isoflavones) were comprehensively identified and quantified from young leaves of 21 core-collected soybean cultivars based on ultra-performance liquid chromatography-diode array detector with quadrupole time of flight/mass spectrometry (UPLC-DAD-QToF/MS). Among total flavonoids from soybean leaves (SLs), the abundant flavonols (83.6%) were primarily composed of di- and tri- glycosides combined to the aglycones (K, kaempferol; Q, quercetin; I, isorhamnetin). Particularly, K-rich SLs (yellow coated seed), Nongrim 51 (breeding line) and YJ208-1 (landrace) contained mainly kaempferol 3-O-(2″-O-glucosyl-6″-O-rhamnosyl)galactoside and 3-O-(2″,6″-di-O-rhamnosyl)galactoside, and were expected to be superior cultivars by their higher flavonoids. Besides, the new tri-I-glycosides (soyanins I–V) were presented as predominant components in Junyeorikong (landrace, black). Thus, this study suggest that the SLs can be considered as valuable edible resources due to their rich flavonoids. Also, these detailed profiles will support breeding of superior varieties with excellent biological activities as well as relationship with seed anthocyanins production, and contribute to perform metabolomics approach to investigate the changes of SLs flavonols during the leaf growth and fermentation in further research.

Both Two CtACO3 Transcripts Promoting the Accumulation of the Flavonoid Profiles in Overexpressed Transgenic Safflower

The unique flavonoids, quinochalcones, such as hydroxysafflor yellow A (HSYA) and carthamin, in the floret of safflower showed an excellent pharmacological effect in treating cardiocerebral vascular disease, yet the regulating mechanisms governing the flavonoid biosynthesis are largely unknown. In this study, CtACO3, the key enzyme genes required for the ethylene signaling pathway, were found positively related to the flavonoid biosynthesis at different floret development periods in safflower and has two CtACO3 transcripts, CtACO3-1 and CtACO3-2, and the latter was a splice variant of CtACO3 that lacked 5' coding sequences. The functions and underlying probable mechanisms of the two transcripts have been explored. The quantitative PCR data showed that CtACO3-1 and CtACO3-2 were predominantly expressed in the floret and increased with floret development. Subcellular localization results indicated that CtACO3-1 was localized in the cytoplasm, whereas CtACO3-2 was localized in the cytoplasm and nucleus. Furthermore, the overexpression of CtACO3-1 or CtACO3-2 in transgenic safflower lines significantly increased the accumulation of quinochalcones and flavonols. The expression of the flavonoid pathway genes showed an upward trend, with CtCHS1, CtF3H1, CtFLS1, and CtDFR1 was considerably induced in the overexpression of CtACO3-1 or CtACO3-2 lines. An interesting phenomenon for CtACO3-2 protein suppressing the transcription of CtACO3-1 might be related to the nucleus location of CtACO3-2. Yeast two-hybrid (Y2H), glutathione S-transferase (GST) pull-down, and BiFC experiments revealed that CtACO3-2 interacted with CtCSN5a. In addition, the interactions between CtCSN5a and CtCOI1, CtCOI1 and CtJAZ1, CtJAZ1 and CtbHLH3 were observed by Y2H and GST pull-down methods, respectively. The above results suggested that the CtACO3-2 promoting flavonoid accumulation might be attributed to the transcriptional activation of flavonoid biosynthesis genes by CtbHLH3, whereas the CtbHLH3 might be regulated through CtCSN5-CtCOI1-CtJAZ1 signal molecules. Our study provided a novel insight of CtACO3 affected the flavonoid biosynthesis in safflower.

Supervised Statistical Learning Prediction of Soybean Varieties and Cultivation Sites Using Rapid UPLC-MS Separation, Method Validation, and Targeted Metabolomic Analysis of 31 Phenolic Compounds in the Leaves

Soybean (Glycine max; SB) leaf (SL) is an abundant non-conventional edible resource that possesses value-adding bioactive compounds. We predicted the attributes of SB based on the metabolomes of an SL using targeted metabolomics. The SB was planted in two cities, and SLs were regularly obtained from the SB plant. Nine flavonol glycosides were purified from SLs, and a validated simultaneous quantification method was used to establish rapid separation by ultrahigh-performance liquid chromatography-mass detection. Changes in 31 targeted compounds were monitored, and the compounds were discriminated by various supervised machine learning (ML) models. Isoflavones, quercetin derivatives, and flavonol derivatives were discriminators for cultivation days, varieties, and cultivation sites, respectively, using the combined criteria of supervised ML models. The neural model exhibited higher prediction power of the factors with high fitness and low misclassification rates while other models showed lower. We propose that a set of phytochemicals of SL is a useful predictor for discriminating characteristics of edible plants.

Metabolite Profiling and Transcriptome Analysis Explains Difference in Accumulation of Bioactive Constituents in Licorice (Glycyrrhiza uralensis) Under Salt Stress

Salinity stress significantly affects the contents of bioactive constituents in licorice Glycyrrhiza uralensis. To elucidate the molecular mechanism underlying the difference in the accumulation of these constituents under sodium chloride (NaCl, salt) stress, licorice seedlings were treated with NaCl and then subjected to an integrated transcriptomic and metabolite profiling analysis. The transcriptomic analysis results identified 3,664 differentially expressed genes (DEGs) including transcription factor family MYB and basic helix-loop-helix (bHLH). Most DEGs were involved in flavonoid and terpenoid biosynthesis pathways. In addition, 121 compounds including a triterpenoid and five classes of flavonoids (isoflavone, flavone, flavanone, isoflavan, and chalcone) were identified, and their relative levels were compared between the stressed and control groups using data from the ultrafast liquid chromatography (UFLC)-triple quadrupole-time of flight-tandem mass spectrometry (TOF-MS/MS) analysis. Putative biosynthesis networks of the flavonoids and triterpenoids were created and combined with structural DEGs such as phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase [4CL], cinnamate 4-hydroxylase [C4H], chalcone synthase [CHS], chalcone-flavanone isomerase [CHI], and flavonoid-3',5' hydroxylase (F3',5'H) for flavonoids, and CYP88D6 and CYP72A154 for glycyrrhizin biosynthesis. Notably, significant upregulation of UDP-glycosyltransferase genes (UGT) in salt-stressed licorice indicated that postmodification of glycosyltransferase may participate in downstream biosynthesis of flavonoid glycosides and triterpenoid saponins. Accordingly, the expression trend of the DEGs is positively correlated with the accumulation of glycosides. Our study findings indicate that key DEGs and crucial UGT genes co-regulate flavonoid and saponin biosynthesis in licorice under salt stress.

Homogenate-Ultrasound-Assisted Ionic Liquid Extraction of Total Flavonoids from Selaginella involven: Process Optimization, Composition Identification, and Antioxidant Activity

In this paper, an efficient approach to extract total flavonoids (TFs) from Selaginella involvens (Sw.) Spring using homogenate-ultrasound-assisted ionic liquid (IL) extraction (HUA-ILE) was first developed. The results indicated that EPyBF4 was selected as the suitable extractant. According to the single factor experiment and response surface methodology, the IL concentration of 0.10 mol/L, the extraction time of 160 s, the liquid/solid ratio of 13:1 mL/g, and the extraction power of 300 W were concluded as the best conditions. A yield of 8.48 ± 0.27 mg/g TF content was obtained. Compared with HUA ethanol extraction, ultrasound-assisted IL extraction, and percolation extraction, the TF content obtained by the HUA-ILE method could be increased by 2 to 4 times, and the extraction time could be reduced by 100 times. Furthermore, 16 compounds of the TF extract were finally identified through ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry, among which 11 compounds were first discovered in S. involven. The contents of six biflavonoids in S. involven were determined simultaneously adopting high-performance liquid chromatography, including amentoflavone, hinokiflavone, bilobetin, ginkgetin, isoginkgetin, and heveaflavone. The TF extract in S. involven was proved to have potent antioxidant activity through the four antioxidant experiments. In conclusion, HUA-ILE was applied for the first time to exploit a green, efficient, and novel approach to extract TFs, and the research also provided promising prospects for applications of S. involven.

Synergistic Effect of Methyl Jasmonate and Abscisic Acid Co-Treatment on Avenanthramide Production in Germinating Oats

The oat (Avena sativa L.) is a grain of the Poaceae grass family and contains many powerful anti-oxidants, including avenanthramides as phenolic alkaloids with anti-inflammatory, anti-oxidant, anti-itch, anti-irritant, and anti-atherogenic activities. Here, the treatment of germinating oats with methyl jasmonate (MeJA) or abscisic acid (ABA) resulted in 2.5-fold (582.9 mg/kg FW) and 2.8-fold (642.9 mg/kg FW) increase in avenanthramide content, respectively, relative to untreated controls (232.6 mg/kg FW). Moreover, MeJA and ABA co-treatment synergistically increased avenanthramide production in germinating oats to 1505 mg/kg FW. Individual or combined MeJA and ABA treatment increased the expression of genes encoding key catalytic enzymes in the avenanthramide-biosynthesis pathway, including hydroxycinnamoyl-CoA:hydrocyanthranilate N-hydroxycinnamoyl transferase (HHT). Further analyses showed that six AsHHT genes were effectively upregulated by MeJA or ABA treatment, especially AsHHT4 for MeJA and AsHHT5 for ABA, thereby enhancing the production of all three avenanthramides in germinating oats. Specifically, AsHHT5 exhibited the highest expression following MeJA and ABA co-treatment, indicating that AsHHT5 played a more crucial role in avenanthramide biosynthesis in response to MeJA and ABA co-treatment of germinating oats. These findings suggest that elicitor-mediated metabolite farming using MeJA and ABA could be a valuable method for avenanthramide production in germinating oats.

Isoflavone-enriched soybean leaves attenuate ovariectomy-induced osteoporosis in rats by anti-inflammatory activity

BACKGROUND

With an increasing aging population, postmenopausal osteoporosis has become a global public health problem. Previous evidence has shown that postmenopausal osteoporosis is a skeletal disease mainly caused by estrogen deficiency, generally accompanied by inflammation, and dietary isoflavones may ameliorate postmenopausal osteoporosis by anti-inflammatory activity. We have generated isoflavone-enriched soybean leaves (IESLs), but their anti-inflammatory activity and effect on attenuating osteoporosis are still obscure. Here, we determined the isoflavone profiles of IESLs and evaluated their anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 cells and anti-osteoporotic effects on ovariectomy-induced osteoporosis in rats.

RESULTS

IESLs had a high content of total isoflavone. Hydrolysate of IESLs (HIESLs) was rich with the aglycones daidzein and genistein, and HIESLs can significantly inhibit lipopolysaccharide-induced inflammation by reducing messenger RNA expression of iNOS, COX-2, IL6, and IL1β. Moreover, ovariectomized rats receiving aqueous extracts of IESLs (HIESLs) orally maintained more bone mass than control rats did, which was attributed to inhibition of osteoclastogenesis by downregulating the messenger RNA expression of the bone-specific genes RANKL/OPG, OC, and cathepsin K, and the inflammation-related genes IL6, NFκB, and COX-2.

CONCLUSION

IESLs may attenuate postmenopausal osteoporosis by suppressing osteoclastogenesis with anti-inflammatory activity and be a potential source of functional food ingredients for the prevention of osteoporosis. © 2020 Society of Chemical Industry.

A Significant Change in Free Amino Acids of Soybean (Glycine max L. Merr) through Ethylene Application

In this study, the changes in free amino acids of soybean leaves after ethylene application were characterized based on quantitative and metabolomic analyses. All essential and nonessential amino acids in soybean leaves were enhanced by fivefold (250 to 1284 mg/100 g) and sixfold (544 to 3478 mg/100 g), respectively, via ethylene application. In particular, it was found that asparagine is the main component, comprising approximately 41% of the total amino acids with a twenty-five fold increase (78 to 1971 mg/100 g). Moreover, arginine and branched chain amino acids (Val, Leu, and Ile) increased by about 14 and 2-5 times, respectively. The increase in free amino acid in stem was also similar to the leaves. The metabolites in treated and untreated soybean leaves were systematically identified by gas chromatography-mass spectrometry (GC-MS), and partial variance discriminant analysis (PLS-DA) scores and heat map analysis were given to understand the changes of each metabolite. The application of ethylene may provide good nutrient potential for soybean leaves.

Exogenous Serotonin and Melatonin Regulate Dietary Isoflavones Profoundly through Ethylene Biosynthesis in Soybean [Glycine max (L.) Merr.]

Serotonin and melatonin are important signaling and stress mitigating molecules. However, their role and molecular mechanism in the accumulation of isoflavones are not clearly defined. To elucidate their functions, serotonin and melatonin were applied to in vitro cultures of soybean at different concentrations and analyzed to assess the accumulation of isoflavone content followed by transcript levels of biosynthesis genes at different time intervals. Increased total phenolics, total flavonoids, and different forms of isoflavone content were observed in the treatments. Expression levels of critical genes in isoflavone, ethylene, jasmonic acid, abscisic acid, and melatonin biosynthesis and related transcription factor were quantified. A correlation was observed between the expression of ethylene biosynthesis genes (S-adenosylmethionine synthase and 1-aminocyclopropane-1-carboxylate oxidase) and isoflavone biosynthesis genes (chalcone synthase, chalcone reductase, and isoflavone synthase). We hypothesize that, under serotonin and melatonin treatments, ethylene biosynthesis may play a role in the increase/decrease in isoflavone content in soybean culture.

Comparison of generational effect on proteins and metabolites in non-transgenic and transgenic soybean seeds through the insertion of the cp4-EPSPS gene assessed by omics-based platforms

This work evaluates different generations of transgenic (cp4-EPSPS gene) and non-transgenic soybean plants through proteomics and metabolomics. For proteomics purpose, 24 differentially abundant protein spots were found through 2-D DIGE, being 4 belonging to transgenic plants. From this total, 19 were successfully identified, storage proteins as predominant class. Some identified proteins are involved in growing and cell division, and stress response, such as LEA and dehydrin. For metabolomics, 17 compounds were putatively annotated, mainly belonging to the secondary metabolism, such as flavonoids. From these analyzes, all generations and varieties of the soybean are prone to be differentiate by PLS-DA. According to our results, transgenic plants appear to be more stable than non-transgenic ones. In addition, the omics-based approaches allowed access some relations between those differential spot proteins and metabolites, mainly those storage proteins and flavonoid.

Alteration of metabolic profiles in Lemna paucicostata culture and enhanced production of GABA and ferulic acid by ethephon treatment

Lemna species have been used in the food, feed, and pharmaceutical industries, as they are inexpensive sources of proteins, starches, and fatty acids. In this study, we treated L. paucicostata with different concentrations (0.05, 0.1, 0.2, 0.5, or 1 mM) of ethephon. The total dry weight decreased in all ethephon-treated groups compared to the control group. We also investigated the alteration of metabolic profiles induced by ethephon treatment by using gas chromatography-mass spectrometry. This analysis identified 48 metabolites, and the relative levels of most of alcohols, amino acids, fatty acids, and phenols increased by the ethephon treatment, whereas levels of organic acids and sugars decreased. Among these, the highest production of γ-aminobutyric acid (GABA, 5.041 ± 1.373 mg/L) and ferulic acid (0.640 ± 0.071 mg/L) was observed in the 0.5 mM and the 0.2 mM ethephon treatment groups, respectively. These results could be useful for large-scale culture of L. paucicostata with enhanced GABA and ferulic acid content for utilization in the food, feed, cosmetic, and pharmaceutical industries.

De novo transcriptomic analysis of light-induced flavonoid pathway, transcription factors in the flower buds of Lonicera japonica

KEY MESSAGE

Transcriptomic analysis of the relationship between gene expression patterns and flavonoid contents in the flower buds of Lonicera japonica under light-induced conditions, especially the flavonoid pathway genes and transcription factors.

ABSTRACT

Flos Lonicerae Japonicae (FLJ), the flower buds of Lonicera japonica Thunb., has been used to treat some human diseases including severe respiratory syndromes and hand-foot-and-mouth diseases owing to its putative antibacterial, and antiviral effects. Luteoloside is a flavonoid that is used by the Chinese Pharmacopoeia to evaluate the quality of FLJ. Light is an important environmental factor that affects flavonoid biosynthesis in the flower buds of L. japonica. However, how light triggers increases in flavonoid production remains unclear. To enhance our understanding of the mechanism involved in light-regulated flavonoid biosynthesis, we sequenced the transcriptomes of L. japonica exposed to three different light conditions: 100% light intensity (CK), 50% light intensity (LI50), and 25% light intensity (LI25) using an Illumina HiSeq 4000 System. A total of 77,297 unigenes with an average length of 809 bp were obtained. Among them, 43,334 unigenes (56.06%) could be matched to at least one biomolecular database. Additionally, 4188, 1545 and 1023 differentially expressed genes (DEGs) were identified by comparative transcriptomics LI25-vs-CK, LI50-vs-CK, and LI25-vs-LI50, respectively. Of note, genes known to be involved in flavonoid biosynthesis, such as 4-coumarate coenzyme A ligase (4CL), and chalcone synthase (CHS) were up-regulated. In addition, a total of 1649 transcription factors (TFs) were identified and divided into 58 TF families; 98 TFs exhibited highly dynamic changes in response to light intensity. Quantitative real-time PCR (qRT-PCR) was used to test the expression profiles of the RNA sequencing (RNA-Seq) data. This study offers insight into how transcriptional expression pattern is influenced by light in the flower buds of L. japonica, and will enhance the understanding of molecular mechanisms of flavonoid biosynthesis in response to light in L. japonica.

Effects of Different Oligochitosans on Isoflavone Metabolites, Antioxidant Activity, and Isoflavone Biosynthetic Genes in Soybean ( Glycine max) Seeds during Germination

Five oligochitosans with increasing degrees of polymerization (DPs), i.e., from chitotriose to chitoheptaose, were examined to clarify the structure-bioactivity relationship between the DPs of oligochitosans and their effects on the isoflavone metabolites, total phenolic and flavonoid contents (TPC and TFC, respectively), and antioxidant activity of soybean ( Glycine max) seeds during germination. Oligochitosans of different DPs exhibited varying influences on the TPC, TFC, and antioxidant activities of soybean seeds. Chitohexaose exerted a strong effect and significantly increased the aforementioned parameters in soybean seeds 72 h after germination. Genistin, malonylgenistin, and genistein were the main isoflavones found, and the genistin and genistein contents were significantly enhanced by 67.32% and 131.38%, respectively, after chitohexaose treatment. Several critical genes involved in the isoflavone biosynthesis (i.e., PAL, CHS, CHI, IFS) of soybeans treated with and without chitohexaose were analyzed, and results suggested that chitohexaose application could dramatically stimulate the transcription of these genes.

Comparative phosphoproteome analysis upon ethylene and abscisic acid treatment in Glycine max leaves

Abscisic acid (ABA) and ethylene play key roles in growth and development of plants. Several attempts have been made to investigate the ABA and ethylene-induced signaling in plants, however, the involvement of phosphorylation and dephosphorylation in fine-tuning of the induced response has not been investigated much. Here, a phosphoproteomic analysis was carried out to identify the phosphoproteins in response to ABA, ethylene (ET) and combined ABA + ET treatments in soybean leaves. Phosphoproteome analysis led to the identification of 802 phosphopeptides, representing 422 unique protein groups. A comparative analysis led to the identification of 40 phosphosites that significantly changed in response to given hormone treatments. Functional annotation of the identified phosphoproteins showed that these were majorly involved in nucleic acid binding, signaling, transport and stress response. Localization prediction showed that 67% of the identified phosphoproteins were nuclear, indicating their potential involvement in gene regulation. Taken together, these results provide an overview of the ABA, ET and combined ABA + ET signaling in soybean leaves at phosphoproteome level.

Methyl Jasmonate Increases Isoflavone Production in Soybean Cell Cultures by Activating Structural Genes Involved in Isoflavonoid Biosynthesis

Isoflavonoids are a class of biologically active natural products that accumulate in soybean ( Glycine max L.) seeds during development, play vital roles in plant defense, and act as phytoestrogens with important human health benefits. Plant cell suspension cultures represent an excellent source of biologically important secondary metabolites. We found that methyl jasmonate (MJ) treatment increased isoflavone production in soybean suspension cell cultures. To investigate the underlying mechanism, we examined the expression of structural genes ( CHS6, CHS7, CHI1, IFS1, IFS2, IFMaT, and HID) in the isoflavonoid biosynthesis pathways in soybean suspension cells under various abiotic stress conditions. MJ treatment had the most significant effect on gene expression and increased the production of three glycosidic isoflavones (daidzin, malonyldaidzin, and malonylgenistin), with the maximum total isoflavone production (∼10-fold increase) obtained on day 9 after MJ application. MJ treatment significantly increased total phenolic contents and upregulated isoflavonoid biosynthesis genes, shedding light on the underlying mechanism.

A Multi-Omics Analysis of Glycine max Leaves Reveals Alteration in Flavonoid and Isoflavonoid Metabolism Upon Ethylene and Abscisic Acid Treatment

Phytohormones are central to plant growth and development. Despite the advancement in our knowledge of hormone signaling, downstream targets, and their interactions upon hormones action remain largely fragmented, especially at the protein and metabolite levels. With an aim to get new insight into the effects of two hormones, ethylene (ET) and abscisic acid (ABA), this study utilizes an integrated proteomics and metabolomics approach to investigate their individual and combined (ABA+ET) signaling in soybean leaves. Targeting low-abundance proteins, our previously established protamine sulfate precipitation method was applied, followed by label-free quantification of identified proteins. A total of 4129 unique protein groups including 1083 differentially modulated in one (individual) or other (combined) treatments were discerned. Functional annotation of the identified proteins showed an increased abundance of proteins related to the flavonoid and isoflavonoid biosynthesis and MAPK signaling pathway in response to ET treatment. HPLC analysis showed an accumulation of isoflavones (genistin, daidzein, and genistein) upon ET treatment, in agreement with the proteomics results. A metabolome analysis assigned 79 metabolites and further confirmed the accumulation of flavonoids and isoflavonoids in response to ET. A potential cross-talk between ET and MAPK signaling, leading to the accumulation of flavonoids and isoflavonoids in soybean leaves is suggested.

Solar UV-B radiation and ethylene play a key role in modulating effective defenses against Anticarsia gemmatalis larvae in field-grown soybean

Solar UV-B radiation has been reported to enhance plant defenses against herbivore insects in many species. However, the mechanism and traits involved in the UV-B mediated increment of plant resistance are unknown in crops species, such as soybean. Here, we studied defense-related responses in undamaged and Anticarsia gemmatalis larvae-damaged leaves of two soybean cultivars grown under attenuated or full solar UV-B radiation. We determined changes in jasmonates, ethylene (ET), salicylic acid, trypsin protease inhibitor activity, flavonoids, and mRNA expression of genes related with defenses. ET emission induced by Anticarsia gemmatalis damage was synergistically increased in plants grown under solar UV-B radiation and was positively correlated with malonyl genistin concentration, trypsin proteinase inhibitor activity and expression of IFS2, and the pathogenesis protein PR2, while was negatively correlated with leaf consumption. The precursor of ET, aminocyclopropane-carboxylic acid, applied exogenously to soybean was sufficient to strongly induce leaf isoflavonoids. Our results showed that in field-grown soybean isoflavonoids were regulated by both herbivory and solar UV-B inducible ET, whereas flavonols were regulated by solar UV-B radiation only and not by herbivory or ET. Our study suggests that, although ET can modulate UV-B-mediated priming of inducible plant defenses, some plant defenses, such as isoflavonoids, are regulated by ET alone.