Water deficit affected flavonoid accumulation by regulating hormone metabolism in Scutellaria baicalensis Georgi roots

Transcriptome-Wide Identification and Expression Analysis of bHLH Family Genes in Iris domestica under Drought and Cu Stress

The role of bHLH transcription factors in plant response to abiotic stress and regulation of flavonoid metabolism is well documented. However, to date, the bHLH transcription factor family in Iris domestica remains unreported, impeding further research on flavonoid metabolism in this plant. To address this knowledge gap, we employed bioinformatics to identify 39 IdbHLH genes and characterised their phylogenetic relationships and gene expression patterns under both drought and copper stress conditions. Our evolutionary tree analysis classified the 39 IdbHLHs into 17 subfamilies. Expression pattern analysis revealed that different IdbHLH transcription factors had distinct expression trends in various organs, suggesting that they might be involved in diverse biological processes. We found that IdbHLH36 was highly expressed in all organs (Transcripts Per Million (TPM) > 10), while only 12 IdbHLH genes in the rhizome and four in the root were significantly upregulated under drought stress. Of these, four genes (IdbHLH05, -37, -38, -39) were co-upregulated in both the rhizome and root, indicating their potential role in drought resistance. With regards to copper stress, we found that only 12 genes were upregulated. Further co-expression analysis revealed that most bHLH genes were significantly correlated with key enzyme genes involved in isoflavone biosynthesis. Thereinto, IdbHLH06 showed a significant positive correlation with IdC4H1 and Id4CL1 (p < 0.05). Furthermore, a transient expression assay confirmed that the IdbHLH06 protein was localised in the nucleus. Our findings provide new insights into the molecular basis and regulatory mechanisms of bHLH transcription factors in isoflavone biosynthesis in I. domestica.

Drought stress-responsive abscisic acid and salicylic acid crosstalk with the phenylpropanoid pathway in soybean seeds

Crosstalk between hormones and secondary metabolites regulates the interactions between plants and stress. However, little is known about the effects of hormone crosstalk on the concentration of flavonoids in seeds. In this study, we identified abscisic acid (ABA) as a negative regulator of flavonoid accumulation in soybean seeds under drought-stress conditions. Alterations in flavonoid accumulation at several intensities of water stress, followed by a recovery period, were measured during the soybean seed-filling stage. Low soil moisture (SM 10%) significantly decreased the total flavonoid content in seeds. The decline in flavonoid content was proportional to the severity of drought stress and was dependent on the activities of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS), two key phenylpropanoid pathway enzymes. The expression of phenylalanine ammonia-lyase 1 (GmPAL1), chalcone isomerase 1A (GmCHI1A), and chalcone synthase 8 (GmCHS8) was associated with phenolic and flavonoid accumulation in soybean seeds of plants subjected to drought stress. Interestingly, the expression levels of GmCHS8 were highly correlated with flavonoid levels under drought stress and water recovery conditions. Cinnamic acid, which is a biosynthesis precursor shared by both phenylpropanoid metabolism and salicylic acid (SA) biosynthesis, decreased under drought stress conditions. Notably, exogenous ABA suppressed the expression of GmPAL1, which encodes the first rate-limiting enzyme in the phenylpropanoid biosynthesis pathway and affects downstream products such as SA and flavonoids. In conclusion, drought stress altered the phenylpropanoid-derived compounds, at least with regard to flavonoid and SA accumulation in seeds, which was regulated by antagonistic interactions with ABA.

Titanium dioxide nanoparticles improve element uptake, antioxidant properties, and essential oil productivity of Melissa officinalis L. seedlings under in vitro drought stress

In vitro drought stress has a considerable impact on the mass production of active compounds in medicinal plants. Nevertheless, photosynthesis, nutrient uptake, and protein synthesis may be negatively affected by drought, which results in poor growth. Titanium dioxide nanoparticles (TiO2 NPs) have recently been shown to play an important role in increasing nutrient uptake, resistance to various environmental stresses, and better plant growth. Regarding the importance of pharmaceutical metabolites of Melissa officinalis L., this experiment aimed to assess the role of TiO2 NPs in improving physiological responses and phytochemical properties in M. officinalis under in vitro drought stress. For this, two-week-old seedlings were cultured on Murashige and Skoog (MS) medium supplemented with 0, 50, and 100 mg L-1 TiO2 NPs and 0, 3, and 6% (w/v) polyethylene glycol (PEG). Two weeks after treatments, a reduction of chlorophyll, protein content, essential elements, and enhancement of H2O2 and malondialdehyde (MDA) levels were seen as a result of drought stress. It was observed that M. officinalis partially responded to the drought by increasing non-enzymatic antioxidants, including phenolics, flavonoids, and anthocyanin and ascorbate peroxidase activity. Moreover, PEG-induced drought stress increased some important essential oil content such as limonene, alpha-pinene, myrcene, γ-3-carene, citral, and carvacrol; however, the results showed that TiO2 NPs not only increased the quantity of essential oils but also led to tolerance to the drought stress by increasing photosynthetic pigments, antioxidant systems, absorption of essential nutrients, and decreasing H2O2 and MDA levels.

From Nature to Lab: A Review of Secondary Metabolite Biosynthetic Pathways, Environmental Influences, and In Vitro Approaches

Secondary metabolites are gaining an increasing importance in various industries, such as pharmaceuticals, dyes, and food, as is the need for reliable and efficient methods of procuring these compounds. To develop sustainable and cost-effective approaches, a comprehensive understanding of the biosynthetic pathways and the factors influencing secondary metabolite production is essential. These compounds are a unique type of natural product which recognizes the oxidative damage caused by stresses, thereby activating the defence mechanism in plants. Various methods have been developed to enhance the production of secondary metabolites in plants. The elicitor-induced in vitro culture technique is considered an efficient tool for studying and improving the production of secondary metabolites in plants. In the present review, we have documented various biosynthetic pathways and the role of secondary metabolites under diverse environmental stresses. Furthermore, a practical strategy for obtaining consistent and abundant secondary metabolite production via various elicitation agents used in culturing techniques is also mentioned. By elucidating the intricate interplay of regulatory factors, this review paves the way for future advancements in sustainable and efficient production methods for high-value secondary metabolites.

Proteomic Insights of Cowpea Response to Combined Biotic and Abiotic Stresses

The co-occurrence of biotic and abiotic stresses in agricultural areas severely affects crop performance and productivity. Drought is one of the most adverse environmental stresses, and its association with root-knot nematodes further limits the development of several economically important crops, such as cowpea. Plant responses to combined stresses are complex and require novel adaptive mechanisms through the induction of specific biotic and abiotic signaling pathways. Therefore, the present work aimed to identify proteins involved in the resistance of cowpea to nematode and drought stresses individually and combined. We used the genotype CE 31, which is resistant to the root-knot nematode Meloidogyne spp. And tolerant to drought. Three biological replicates of roots and shoots were submitted to protein extraction, and the peptides were evaluated by LC-MS/MS. Shotgun proteomics revealed 2345 proteins, of which 1040 were differentially abundant. Proteins involved in essential biological processes, such as transcriptional regulation, cell signaling, oxidative processes, and photosynthesis, were identified. However, the main defense strategies in cowpea against cross-stress are focused on the regulation of hormonal signaling, the intense production of pathogenesis-related proteins, and the downregulation of photosynthetic activity. These are key processes that can culminate in the adaptation of cowpea challenged by multiple stresses. Furthermore, the candidate proteins identified in this study will strongly contribute to cowpea genetic improvement programs.

Phylogenetic Analysis of R2R3-MYB Family Genes in Tetrastigma hemsleyanum Diels et Gilg and Roles of ThMYB4 and ThMYB7 in Flavonoid Biosynthesis

Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is an extensively used Chinese folk herb with multiple bioactivities. Among these bioactivities, flavonoids are recognized as the representative active ingredients. We previously found an elevated accumulation of flavonoids in T. hemsleyanum under water stress; however, the mechanism remains unclear. R2R3-MYB transcription factors play vital roles in the plant response to environmental stress and the regulation of secondary metabolites. Herein, a systematic transcriptome identification of R2R3-MYB family genes under water stress in T. hemsleyanum was performed to explore their potential function in the biosynthesis of flavonoids. A total of 26 R2R3-MYB genes were identified, most of which were clustered into functional branches of abiotic stress. ThMYB4 and ThMYB7 were then screened out to be associated with the biosynthesis of flavonoids through a protein-protein interaction prediction. An expression correlation analysis based on RNA-seq further confirmed that ThMYB4 and ThMYB7 were positively related to the flavonoid biosynthetic pathway genes of T. hemsleyanum. In ThMYB4- and ThMYB7-overexpression hairy roots, it was found that the expression of ThCHS and ThCHI was significantly increased, suggesting that ThMYB4 and ThMYB7 may act as regulators in flavonoid biosynthesis. This will shed new light on the promotion of flavonoid production and the medicinal value of T. hemsleyanum by manipulating transcription factors.

Identification of drought-responsive phenolic compounds and their biosynthetic regulation under drought stress in Ligularia fischeri

Ligularia fischeri, a leafy edible plant found in damp shady regions, has been used as an herbal medicine and is also consumed as a horticultural crop. In this study, we investigated the physiological and transcriptomic changes, especially those involved in phenylpropanoid biosynthesis, induced by severe drought stress in L. fischeri plants. A distinguishing characteristic of L. fischeri is a color change from green to purple due to anthocyanin biosynthesis. We chromatographically isolated and identified two anthocyanins and two flavones upregulated by drought stress using liquid chromatography-mass spectrometry and nuclear magnetic resonance analyses in this plant for the first time. In contrast, all types of caffeoylquinic acids (CQAs) and flavonol contents were decreased under drought stress. Further, we performed RNA sequencing to examine the molecular changes in these phenolic compounds at the transcriptome level. In an overview of drought-inducible responses, we identified 2,105 hits for 516 distinct transcripts as drought-responsive genes. Moreover, differentially expressed genes (DEGs) associated with phenylpropanoid biosynthesis accounted for the greatest number of both up- and downregulated DEGs by Kyoto Encyclopedia of Genes and Genomes enrichment analysis. We identified 24 meaningful DEGs based on the regulation of phenylpropanoid biosynthetic genes. Potential drought-responsive genes included upregulated flavone synthase (LfFNS, TRINITY DN31661 c0 g1 i1) and anthocyanin 5-O-glucosyltransferase (LfA5GT1, TRINITY DN782 c0 g1 i1), which could contribute to the high levels of flavones and anthocyanins under drought stress in L. fischeri. In addition, the downregulated shikimate O-hydroxycinnamolytransferase (LfHCT, TRINITY DN31661 c0 g1 i1) and hydroxycinnamoyl-CoA quinate/shikimate transferase (LfHQT4, TRINITY DN15180 c0 g1 i1) genes led to a reduction in CQAs. Only one or two BLASTP hits for LfHCT were obtained for six different Asteraceae species. It is possible that the HCT gene plays a crucial role in CQAs biosynthesis in these species. These findings expand our knowledge of the response mechanisms to drought stress, particularly regarding the regulation of key phenylpropanoid biosynthetic genes in L. fischeri.

Exogenous melatonin ameliorates drought stress in Agropyron mongolicum by regulating flavonoid biosynthesis and carbohydrate metabolism

Drought is one of the most common abiotic stressors in plants. Melatonin (MT) is a high-efficiency and low-toxicity growth regulator that plays an important role in plant responses to drought stress. As a wild relative of wheat, Agropyron mongolicum has become an important species for the improvement of degraded grasslands and the replanting of sandy grasslands. However, the physiological and molecular mechanisms by which exogenous MT regulates drought stress in A. mongolicum remain unclear. To assess the effectiveness of MT intervention (100 mg·L^-1), polyethylene glycol 6000 was used to simulate drought stress, and its ameliorating effects on drought stress in A. mongolicum seedlings were investigated through physiology, transcriptomics, and metabolomics. Physiological analysis indicated that MT treatment increased the relative water content and chlorophyll content and decreased the relative conductivity of A. mongolicum seedlings. Additionally, MT decreased malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation by enhancing antioxidant enzyme activities. The transcriptome and metabolite profiling analysis of A. mongolicum seedlings treated with and without MT under drought stress identified the presence of 13,466 differentially expressed genes (DEGs) and 271 differentially expressed metabolites (DEMs). The integrated analysis of transcriptomics and metabolomics showed that DEGs and DEMs participated in diverse biological processes, such as flavonoid biosynthesis and carbohydrate metabolism. Moreover, MT may be involved in regulating the correlation of DEGs and DEMs in flavonoid biosynthesis and carbohydrate metabolism during drought stress. In summary, this study revealed the physiological and molecular regulatory mechanisms of exogenous MT in alleviating drought stress in A. mongolicum seedlings, and it provides a reference for the development and utilization of MT and the genetic improvement of drought tolerance in plants from arid habitats.

Different adaptive patterns of wheat with different drought tolerance under drought stresses and rehydration revealed by integrated metabolomic and transcriptomic analysis

Wheat as a staple food crop is enduring ever-frequent intermittent and changing drought with the climate change. It is of great significance to highlight the adaptive approaches under such variable conditions at multiple levels to provide a comprehensive understanding of drought tolerance and facilitate the genetic breeding of wheat. Therefore, three wheat lines with different drought tolerance (drought-tolerant mutant Mu > common wheat CK > drought susceptible mutant mu) were analyzed under moderate and severe drought stresses as well as rehydration. Samples were subjected to transcriptomic and metabolomic profiling in combination with physiological and biochemical determination. The moderate drought stress rendered 198 and 115 differentially expressed metabolites (DEMs) in CK and Mu, respectively. The severe drought stress rendered 166, 151 and 137 DEMs in CK, Mu and mu, respectively. The rehydration rendered 150 and 127 DEMs in CK and Mu. 12,557 and 10,402 differentially expressed genes (DEGs) were identified for CK and Mu under moderate drought stress, respectively. 9,893, 7,924, and 9,387 DEGs were identified for CK, Mu, and mu under severe drought stress, respectively. 13,874 and 14,839 were identified in CK and Mu under rehydration, respectively. Metabolomics results showed that amino acid was the most differentially expressed metabolites, followed by phenolic acids. Flavonoids played an important role in drought tolerance. Most enriched pathways under drought included biosynthesis of secondary metabolites, metabolic pathways and photosynthesis. Metabolites and genes involved in osmotic regulation, antioxidase activities, and ABA signaling were more enriched in Mu than in CK and mu. Various drought-responsive genes and metabolites in Mu showed different trends with those in CK and mu. Increased amino acids biosynthetic capability and ROS scavenging ability resulted from higher antioxidase activities and increased flavonoids may be the mechanisms underlying the drought tolerance characteristic of Mu. Recovery from reversible ROS damage and rapid amino acid biosynthesis may contribute to the rapid recovery of Mu. The present study provides new insights for mechanisms of wheat under complex drought conditions.

Effects of Regulated Deficit Irrigation on Yield and Quality of Isatis indigotica in a Cold and Arid Environment

Although regulated deficit irrigation may improve crop yields, little research has been conducted on the effects of water deficits on Isatis indigotica, a popular herbal medicine. Field experiments were conducted in 2016 and 2017 to study the effects of regulated deficit irrigation on the net photosynthetic rate, yield, water use efficiency (WUE), and quality of I. indigotica in northwest China. Plants at the vegetative and fleshy root growth stages were subjected to mild, moderate, and severe water deficits, and their photosynthetic physiological indexes, yield, and WUE were measured. Moderate and severe deficits, but not a mild deficit, significantly decreased the net photosynthetic rate and dry matter accumulation. The yield and WUE under mild deficit were markedly higher, reaching 8239.56 kg·ha−2 and 8390.80 kg·ha−2, respectively, in the vegetative stage and 24.11 kg·ha−2·mm−1 and 23.62 kg·ha−2·mm−1, respectively, in the fleshy root growth stage, while severe deficits significantly reduced yield and WUE. Mild and moderate deficits increased the content of (R,S)-goitrin, indirubin, and indigo, improving root quality, but severe deficits decreased these compounds. Therefore, a mild water deficit in the vegetative and fleshy root growth stages is optimal and can reduce water consumption and improve I. indigotica quality and WUE without reducing yield.

Differential Expression of Calycosin-7-O-β-D-glucoside Biosynthesis Genes and Accumulation of Related Metabolites in Different Organs of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao Under Drought Stress

Calycosin-7-O-β-D-glycoside (CG), as a flavonoid, plays an important role in the abiotic stress response of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus). CG is also an active ingredient in A. mongholicus with high medicinal value. However, the response mechanism of the CG biosynthetic pathway of drought stress is not clear. In this research, drought stress was inflicted upon A. mongholicus, and the variations in flavonoid metabolites and the correlating gene expression in CG biosynthesis were studied in roots, stems, and leaves of A. mongholicus by UHPLC-MRM-MS/MS and qRT-PCR. Drought stress reduced the dry weight and increased the content of malondialdehyde (MDA) and proline. Drought was beneficial to the accumulation of L-phenylalanine and 4-coumaric acid in leaves and promoted the accumulation of all target compounds in the roots, except calycosin. Overexpression of AmIOMT was observed in the leaves, but the content of formononetin which is the product of isoflavone O-methyltransferase (IOMT) catalysis was higher in stems than in leaves. This research aims to further understand the acclimation of abiotic stress and the regulation mechanism of flavonoid accumulation in A. mongholicus.

Sandbur Drought Tolerance Reflects Phenotypic Plasticity Based on the Accumulation of Sugars, Lipids, and Flavonoid Intermediates and the Scavenging of Reactive Oxygen Species in the Root

The perennial grass Cenchrus spinifex (common sandbur) is an invasive species that grows in arid and semi-arid regions due to its remarkable phenotypic plasticity, which confers the ability to withstand drought and other forms of abiotic stress. Exploring the molecular mechanisms of drought tolerance in common sandbur could lead to the development of new strategies for the protection of natural and agricultural environments from this weed. To determine the molecular basis of drought tolerance in C. spinifex, we used isobaric tags for relative and absolute quantitation (iTRAQ) to identify proteins differing in abundance between roots growing in normal soil and roots subjected to moderate or severe drought stress. The analysis of these proteins revealed that drought tolerance in C. spinifex primarily reflects the modulation of core physiological activities such as protein synthesis, transport and energy utilization as well as the accumulation of flavonoid intermediates and the scavenging of reactive oxygen species. Accordingly, plants subjected to drought stress accumulated sucrose, fatty acids, and ascorbate, shifted their redox potential (as determined by the NADH/NAD ratio), accumulated flavonoid intermediates at the expense of anthocyanins and lignin, and produced less actin, indicating fundamental reorganization of the cytoskeleton. Our results show that C. spinifex responds to drought stress by coordinating multiple metabolic pathways along with other adaptations. It is likely that the underlying metabolic plasticity of this species plays a key role in its invasive success, particularly in semi-arid and arid environments.

Lenthionine, a Key Flavor Substance in Lentinula edodes, Is Regulated by Cysteine under Drought Stress

Due to its unique flavor profile, Lentinula edodes has become one of the most popular edible mushrooms in the world, but the regulatory mechanism of its flavor substances has not been revealed. To study the mechanism that regulates the anabolic metabolism of the important flavor substance lenthionine (LT), the effect of cysteine (Cys) synthesized by the cystathionine-γ-lyase (CSE-1) gene participating in the regulation of LT metabolism under drought stress was analyzed. Our results showed that drought stress promoted the accumulation of LT, and the key genes GTT and LECSL were activated. Furthermore, drought stress promoted the accumulation of intracellular Cys and activated the key gene for Cys synthesis, CSE-1. Both inhibition of the CSE enzyme activity by inhibitors and silencing of the CSE-1 gene under drought stress significantly reduced the intracellular contents of Cys and LT, but the inhibition of LT synthesis disappeared after the exogenous addition of Cys. These results indicate that LT synthesis in L. edodes under drought stress is dependent on Cys. In summary, the mechanism of the regulation of flavor substances in edible mushrooms by the environment was revealed for the first time.

Expression Characterization of Flavonoid Biosynthetic Pathway Genes and Transcription Factors in Peanut Under Water Deficit Conditions

Drought is one of the hostile environmental stresses that limit the yield production of crop plants by modulating their growth and development. Peanut (Arachis hypogaea) has a wide range of adaptations to arid and semi-arid climates, but its yield is prone to loss due to drought. Other than beneficial fatty acids and micronutrients, peanut harbors various bioactive compounds including flavonoids that hold a prominent position as antioxidants in plants and protect them from oxidative stress. In this study, understanding of the biosynthesis of flavonoids in peanut under water deficit conditions was developed through expression analysis and correlational analysis and determining the accumulation pattern of phenols, flavonols, and anthocyanins. Six peanut varieties (BARD479, BARI2011, BARI2000, GOLDEN, PG1102, and PG1265) having variable responses against drought stress have been selected. Higher water retention and flavonoid accumulation have been observed in BARI2011 but downregulation has been observed in the expression of genes and transcription factors (TFs) which indicated the maintenance of normal homeostasis. ANOVA revealed that the expression of flavonoid genes and TFs is highly dependent upon the genotype of peanut in a spatiotemporal manner. Correlation analysis between expression of flavonoid biosynthetic genes and TFs indicated the role of AhMYB111 and AhMYB7 as an inhibitor for AhF3H and AhFLS, respectively, and AhMYB7, AhTTG1, and AhCSU2 as a positive regulator for the expression of Ah4CL, AhCHS, and AhF3H, respectively. However, AhbHLH and AhGL3 revealed nil-to-little relation with the expression of flavonoid biosynthetic pathway genes. Correlational analysis between the expression of TFs related to the biosynthesis of flavonoids and the accumulation of phenolics, flavonols, and anthocyanins indicated coregulation of flavonoid synthesis by TFs under water deficit conditions in peanut. This study would provide insight into the role of flavonoid biosynthetic pathway in drought response in peanut and would aid to develop drought-tolerant varieties of peanut.

Integrated Transcriptome and Metabolome Analysis Revealed That Flavonoid Biosynthesis May Dominate the Resistance of Zanthoxylum bungeanum against Stem Canker

Stem canker of Zanthoxylum bungeanum is a devastating disease that seriously affects the plantation and industrial development of Z. bungeanum due to a lack of effective control measures. The objective of this study was to screen out resistant Z. bungeanum varieties and further explore their resistance mechanisms against stem canker. Results showed that the most resistant and susceptible varieties were, respectively, Doujiao (DJ) and Fengxian Dahongpao (FD). Combining transcriptomic and metabolomic analyses, we found that the genes and metabolites associated with the phenylpropanoid metabolism, especially flavonoid biosynthesis, were highly significantly enriched in DJ following pathogen infection compared with that in FD, which indicated that the flavonoid metabolism may positively dominate the resistance of Z. bungeanum. This finding was further confirmed by quantitative real-time polymerase chain reaction analysis, through which higher expression levels of core genes involved in flavonoid metabolism in resistant variety were observed. Moreover, by analyzing the differences in the flavonoid content in the stems of resistant and susceptible varieties and the antifungal activities of flavonoids extracted from Z. bungeanum stems, the conclusion that flavonoid metabolism positively regulates the resistance of Z. bungeanum was further supported. Our results not only aid in better understanding the resistance mechanisms of Z. bungeanum against stem canker but also promote the breeding and utilization of resistant varieties.

The quality of wild Salvia miltiorrhiza from Dao Di area in China and its correlation with soil parameters and climate factors

INTRODUCTION

Salvia miltiorrhiza is a frequently used herb in traditional Chinese medicine, and tanshinone IIA (Tan IIA) and salvianolic acid B (Sal Acid B) are two major extracts obtained from its dried root. The quality of herbal ingredients can be affected by environmental factors.

OBJECTIVE

To evaluate the quality of wild S. miltiorrhiza and investigate the influence of soil constituents and parameters as well as climatic conditions and factors on the content of Tan IIA and Sal Acid B.

METHODOLOGY

We collected samples in 12 natural locations in the Dao Di area in China, the area in which S. miltiorrhiza grows, that results in a distinctive higher quality of medicinal materials from the harvested plant. The concentrations of Tan IIA and Sal Acid B were measured by high-performance liquid chromatography (HPLC). Soil total carbon, total nitrogen, available nitrogen, available phosphorus, available potassium, and particle size distribution were determined. We also collected climate data using ArcGIS from the WorldClim database, and correlation tests, redundancy, and regression analyses were conducted to analyse the relationship and cluster the samples according to their chemical profile.

RESULTS

The content of Tan IIA and Sal Acid B in most of the samples was significantly different (P < 0.05). Soil available phosphorus was considered as a key factor that influenced the quality of wild S. miltiorrhiza, and we found a significant negative association between the concentration of Tan IIA in roots and soil available phosphorus. Moreover, the accumulation of Tan IIA in S. miltiorrhiza was also significantly associated with precipitation in April, May, and October, maximum temperature in January, and standard deviation of temperature seasonality. There was no significant correlation between the content of Sal Acid B and ecological factors. In addition, samples collected from Mengshan, Hexian, and Lushi locations were rich in Tan IIA and tended to cluster together, whereas samples collected from Longquan and Huoshan locations tended to cluster and were poor in Tan IIA.

CONCLUSION

The Tan IIA content in samples collected from southern Anhui was significantly lower than that in other Dao Di locations. The content of Tan IIA was related more to the soil than the temperature. Compared with Tan IIA, Sal Acid B was less influenced by soil and climate factors. The findings of this study may provide helpful references for quality control of medicinal plants that exert pharmacological effects in humans.

Reduced host plant growth and increased tyrosine-derived secondary metabolites under climate change and negative consequences on its specialist herbivore

Compositive changes in climatic factors, e.g., carbon dioxide (CO₂) and precipitation frequency and intensity, affect the strength of species interactions via responses in plants. Therefore, understanding the effects of climate change on plant-herbivore interactions is important to maintain biodiversity as about 70% of insects are herbivorous. However, the interactive effects of CO₂ and precipitation on plants and consequences for herbivores are poorly understood. Here, we examined how elevated CO₂ and increased watering frequency affect the growth and resistance responses of Aristolochia contorta and the growth performance of its specialist herbivore, Sericinus montela. Elevated CO₂ suppressed growth with decreased photosynthesis ability, and increased resistance in plants. In contrast, increased watering frequency partly ameliorated the negative effects of high CO₂. Growth performance of specialist herbivores decreased under elevated CO₂ condition as a consequence of increased resistance in plants. Due to the significant effects of CO₂, we suggest that both the quantity and the quality of host plants as a food would decline, and the growth performance of its specialist herbivore might be threatened as climate change progresses.

Metabolite Profile and Antioxidant Activity of Some Species of Genus Scutellaria Growing in Bulgaria

Until now, the interest to plants from genus Scutellaria in Bulgaria has been focused mainly on the terpenes in them. The purpose of this study is to enrich the information on the composition of the Bulgarian Scutellaria species in terms of both polyphenolic content as well as primary metabolites such as mono-, oligosaccharides and organic acids. An aerial part of three Scutellaria species growing in four low mountain regions of Southern Bulgaria was used. The flavonoids scutellarin, baicalin, baicalein, wogonin, wogonoside, luteolin, chrysin and a caffeoyl phenylethanoid glycoside-verbascoside have been identified via HPLC in different extracts from Scutellaria altissima, Scutellaria albida and Scutellaria galericulata. The antioxidant activity of the extracts has been evaluated. The Scutellaria altissima from Mezek and Scutellaria galericulata from Parvenets we studied, which are the richest in flavonoids (represented mainly by baicalin, scutellarin and wogonoside), show the highest Oxygen Radical Absorption Capacity. Hydroxyl Radical Averting Capacity of Scutellaria albida from Mezek and Scutellaria altissima from Bachkovo is the most pronounced, probably due to the content of scutellarin and luteolin and chrysin, respectively. Antioxidant activity of aqueous, methanolic and 70% and 96% ethanol extracts were also determined by the electrochemical method.

Transcriptomic and metabolomic profiling of melatonin treated soybean (Glycine max L.) under drought stress during grain filling period through regulation of secondary metabolite biosynthesis pathways

There is a growing need to enhance the productivity of soybean (Glycine max L.) under severe drought conditions in order to improve global food security status. Melatonin, a ubiquitous hormone, could alleviate drought stress in various plants. Earlier, we demonstrated that exogenous melatonin treatment could enhance the tolerance of drought-treated soybean. However, the underlying mechanisms by which this hormone exerts drought resistance is still unclear. The present study used transcriptomic and metabolomic techniques to determine some critical genes and pathways regulating melatonin response to drought conditions. Results showed that exogenous melatonin treatment could increase relative water content and decrease electrolyte leakage in the leaves and increase seed yield under drought stress. Transcriptomic analysis showed that there were 852 core differentially expressed genes (DEGs) that were regulated by drought stress and melatonin in soybean leaves. The most enriched drought-responsive genes are mainly involved in the 'biosynthesis of secondary metabolites'. Metabolomic profiling under drought stress showed higher accumulation levels of secondary metabolites related to drought tolerance after exogenous melatonin treatment. Also, we highlighted the vital role of the pathways including phenylpropanoid, flavonoid, isoflavonoid, and steroid biosynthesis pathways for improvement of drought tolerance in soybean by exogenous melatonin treatment. In all, findings from this study give detailed molecular basis for the application of melatonin as a drought-resistant agent in soybean cultivation.

Applications, phytochemistry, pharmacological effects, pharmacokinetics, toxicity of Scutellaria baicalensis Georgi. and its probably potential therapeutic effects on COVID-19: a review

Scutellaria baicalensis Georgi. (SB) is a common heat-clearing medicine in traditional Chinese medicine (TCM). It has been used for thousands of years in China and its neighboring countries. Clinically, it is mostly used to treat diseases such as cold and cough. SB has different harvesting periods and processed products for different clinical symptoms. Botanical researches proved that SB included in the Chinese Pharmacopoeia (1st, 2020) was consistent with the medicinal SB described in ancient books. Modern phytochemical analysis had found that SB contains hundreds of active ingredients, of which flavonoids are its major components. These chemical components are the material basis for SB to exert pharmacological effects. Pharmacological studies had shown that SB has a wide range of pharmacological activities such as antiinflammatory, antibacterial, antiviral, anticancer, liver protection, etc. The active ingredients of SB were mostly distributed in liver and kidney, and couldn't be absorbed into brain via oral absorption. SB's toxicity was mostly manifested in liver fibrosis and allergic reactions, mainly caused by baicalin. The non-medicinal application prospects of SB were broad, such as antibacterial plastics, UV-resistant silk, animal feed, etc. In response to the Coronavirus Disease In 2019 (COVID-19), based on the network pharmacology research, SB's active ingredients may have potential therapeutic effects, such as baicalin and baicalein. Therefore, the exact therapeutic effects are still need to be determined in clinical trials. SB has been reviewed in the past 2 years, but the content of these articles were not comprehensive and accurate. In view of the above, we made a comprehensive overview of the research progress of SB, and expect to provide ideas for the follow-up study of SB.

Complexity of active medicinal ingredients in radix scutellariae with sodium hydrosulfite exposure

Both plants and animals are living things made up of similar cells as well as organelles, and their essence of life is the same. However, plants face more environmental stress than animals and generate excessive reactive oxygen species (ROS), a group of small molecules that can harm proteins, necessitating distinctive metabolic processes. Secondary metabolites in plants are a group of chemical components that can eliminate ROS and can also exhibit medicinal properties; therefore, herbal medicines are often closely linked to the ecological significance of secondary metabolites. Why plants contain so many, not few, active medicinal ingredients is unknown. The root of Scutellaria baicalensis, a popular herbal medicine, is rich in various flavonoids with diverse structural features. Sodium hydrosulfite (Na₂S₂O₄) can produce O˙^-₂ radicals and induce physical conditions under environmental stress. Using UHPLC-ESI-Q-TOF-MS/MS analysis, a total of 25 different compounds were identified in the roots of S. baicalensis between the Na₂S₂O₄ groups and suitable conditions. Based on the results of the t-test (P<0.05) performed for the groups and ions with values of VIP ≥ 2, the most significantly different chemical markers with Na₂S₂O₄ treatment were shikimic acid, citric acid, baicalin, wogonoside, baicalein, wogonin, 3,5,7,2',6'-pentahydroxyflavanone, 5,2',6'-trihydroxy-7,8-dimethoxy flavone, chrysin, eriodictyol, 5,8-dihydroxy-6,7 -dimethoxy flavone, skullcapflavone Ⅱ, and 5,7-dihydroxy-6,8,2',3'-tetrame thoxyflavone, and most of them were free flavonoids with many phenolic hydroxyl or methoxyl groups and characteristically high antioxidant activities. S. baicalensis roots modified their ability to eliminate ROS and maintained the equilibrium of ROS through the multitudinous biosynthesis and conversion of flavonoids, which is similar to the equilibrium established by an intricate buffer solution and perfectly explains the diversity and complexity of medicinal plant ingredients.

Evaluation of sulfur and foliar application of Zn and Fe on yield and biochemical factors of cumin (Cuminum cyminum L.) under irrigation regimes

Introduction: Cumin, due to its food and medicinal properties, is one of the important plant species in the world. Moreover, water and nutrition deficiencies are serious abiotic stress factors. So, this experiment was conducted with the aim of investigating the effects of sulfur and foliar application of Fe and Zn on yield and biochemical characteristics of cumin under irrigation regimes. Methods: The experiment was conducted as a split plot on the basis of a completely randomized block design during the 2016-2017 growing seasons with three replications. Experimental factors were arranged in irrigation regimes as main plots at three levels (I1: No stress (control), I2: irrigation based on 40% available water discharge, I3: 80% available water discharge) and foliar application of Zinc (Zn) and Iron (Fe) as subplots [F1: control (water-soluble), F2: Iron, F3: Zinc, F4: Zinc and Iron chelate] and sub-sub plots including sulfur fertilizer [S1: control (no use of sulfur), S2: sulfur fertilizer with Thiobacillus]. Results: Analyzed data showed that total phenol content and flavonoids were enhanced with the increase of drought intensity and the maximum amount was recorded under I3, while I3 caused a substantial reduction in grain yield. Flavonoid and grain yield significantly increased in F4. Total phenol content was the highest in F2 and F3 treatments. Application of sulfur fertilizer resulted in a significant increase in peroxidase, phenol and flavonoids. The highest amount of peroxidase was obtained in I3F4 and I3F3. The largest total soluble sugar (TSS) was resulted by I3S2 and the least by I1S1. Foliar application of Zn and Fe with sulfur fertilizer increased TSS. Conclusion: The present study suggests that foliar application of Fe and Zn and sulfur fertilizer can improve the injurious effects of water deficiency on cumin plant through alteration in yield and biochemical characteristics.

Regulation of flavonoid metabolism in ginkgo leaves in response to different day-night temperature combinations

Flavonoids are the most important secondary metabolites in ginkgo (Ginkgo biloba L.) leaves that determine its medicinal quality. Studies have suggested that secondary metabolism is strongly affected by temperature in other plant species, but little is known about ginkgo. In this study, we investigated the effects of different day-night temperature combinations (15/10, 25/20, and 35/30 °C (day/night)) on key enzyme activity, growth regulator concentrations, and flavonoid accumulation in ginkgo leaves. We found that phenylalanine ammonia-lyase (PAL) activity was enhanced and inhibited at 15/10 and 35/30 °C, respectively. Cinnamate-4-hydroxylase (C4H) activity was relatively stable under the three temperature conditions, and the p-coumarate CoA ligase (4CL) activity showed different trends under the three temperature conditions. The concentrations of flavonoid constituents (quercetin, kaempferol, and isorhamnetin) were decreased and increased under the 35/30 and 15/10 °C conditions, respectively. Low temperature promoted soluble sugar accumulation, while temperature had a limited impact on the accumulation of soluble protein. The pattern of change in the total flavonoid concentration was not always in agreement with PAL activity due to its complex pathway. Indoleacetic acid (IAA) and gibberellin (GA) changes shared similar patterns and had limited effects on flavonoid accumulation, while abscisic acid (ABA) acted as a promotor of flavonoid accumulation under high-temperature conditions. The total flavonoids achieved the highest content under the 15/10 °C treatment on the 40th day. Therefore, the lower temperature (15/10 °C) is more favorable for flavonoid accumulation and will provide a theoretical basis for further study.

Plants adapted to arid areas: specialized metabolites

Drought stress affects growth, morphological and biochemical properties in plants. To develop resistance and adapt to drought, plants need metabolic changes. Adaptations to stress involve changes to gene expression that activate metabolic processes that promote drought resistance and that may include biosynthesis and accumulation of specialized metabolites. Such adaptations in specialized metabolism may be important mechanisms leading to plant stress resistance and involve production of phenolics, flavonoids, terpenoid and nitrogen containing compounds that are species and genotype specific. Most plants having special metabolites to adapt to drought stress belong to different botanical families. C3, C4 and CAM plants, apply both morphological and metabolic mechanisms to adapt to drought as well as to accumulate specialized metabolites. Generally, medicinal plants increase their functional metabolites content, when exposed to drought stress. During drought stress, transcription factors and related pathways for biosynthesis of phenolics, flavonoids, anthocyanins as well as for stress jasmonate and abscisic acid stress hormones are activated.

Transcriptomic and Metabolic Insights into the Distinctive Effects of Exogenous Melatonin and Gibberellin on Terpenoid Synthesis and Plant Hormone Signal Transduction Pathway in Camellia sinensis

Melatonin and gibberellin are bioactive molecules in plants. In the present study, the role of exogenous melatonin (MT) and gibberellin (GA) in the tea plant was explored by transcriptome and metabolic analysis. Results showed that the growth of tea plant was enhanced by MT treatment. The pathways of terpenoid synthesis and plant-pathogen interaction were significantly strengthened, combined with the upregulation of LRR-RLK and transcription factors which contributed to the growth of tea plant. The internode elongation and leaf enlargement were hastened by GA treatment. Significantly modulated expression occurred in the plant hormonal signal transduction, complemented by the upregulation of phenylpropanoid biosynthesis and expansins to achieve growth acceleration, whereas the flavonoid synthesis was repressed in GA treatment. Therefore, the distinctive effect of MT and GA treatment on tea plant was different. The MT exhibited significant promotion in terpenoid synthesis, especially, TPS14 and TPS1. GA was prominent in coordinated regulation of plant hormonal signal transduction.

Time-Course Comparative Metabolite Profiling under Osmotic Stress in Tolerant and Sensitive Tibetan Hulless Barley

Tibetan hulless barley is widely grown in the extreme environmental conditions of the Qinghai-Tibet Plateau which is characterized by cold, high salinity, and drought. Osmotic stress always occurs simultaneously with drought and its tolerance is a vital part of drought tolerance. The diversity of metabolites leading to osmotic stress tolerance was characterized using widely-targeted metabolomics in tolerant (XL) and sensitive (D) accessions submitted to polyethylene glycol. XL regulated a more diverse set of metabolites than D, which may promote the establishment of a robust system to cope with the stress in XL. Compounds belonging to the group of flavonoids, amino acids, and glycerophospholipids constitute the core metabolome responsive to the stress, despite the tolerance levels. Moreover, 8 h appeared to be a critical time point for stress endurance involving a high accumulation of key metabolites from the class of nucleotide and its derivative which provide the ultimate energy source for the synthesis of functional carbohydrates, lipids, peptides, and secondary metabolites in XL. This intrinsic metabolic adjustment helped XL to efficiently alleviate the stress at the later stages. A total of 22 diverse compounds were constantly and exclusively regulated in XL, representing novel stress tolerance biomarkers which may help improving stress tolerance, especially drought, in hulless barley.

Response of Plant Secondary Metabolites to Environmental Factors

Plant secondary metabolites (SMs) are not only a useful array of natural products but also an important part of plant defense system against pathogenic attacks and environmental stresses. With remarkable biological activities, plant SMs are increasingly used as medicine ingredients and food additives for therapeutic, aromatic and culinary purposes. Various genetic, ontogenic, morphogenetic and environmental factors can influence the biosynthesis and accumulation of SMs. According to the literature reports, for example, SMs accumulation is strongly dependent on a variety of environmental factors such as light, temperature, soil water, soil fertility and salinity, and for most plants, a change in an individual factor may alter the content of SMs even if other factors remain constant. Here, we review with emphasis how each of single factors to affect the accumulation of plant secondary metabolites, and conduct a comparative analysis of relevant natural products in the stressed and unstressed plants. Expectantly, this documentary review will outline a general picture of environmental factors responsible for fluctuation in plant SMs, provide a practical way to obtain consistent quality and high quantity of bioactive compounds in vegetation, and present some suggestions for future research and development.

Age-related mechanism and its relationship with secondary metabolism and abscisic acid in Aristotelia chilensis plants subjected to drought stress

Drought stress is the most important stress factor for plants, being the main cause of agricultural crop loss in the world. Plants have developed complex mechanisms for preventing water loss and oxidative stress such as synthesis of abscisic acid (ABA) and non-enzymatic antioxidant compounds such as anthocyanins, which might help plants to cope with abiotic stress as antioxidants and for scavenging reactive oxygen species. A. chilensis (Mol.) is a pioneer species, colonizing and growing on stressed and disturbed environments. In this research, an integrated analysis of secondary metabolism in Aristotelia chilensis was done to relate ABA effects on anthocyanins biosynthesis, by comparing between young and fully-expanded leaves under drought stress. Plants were subjected to drought stress for 20 days, and physiological, biochemical, and molecular analyses were performed. The relative growth rate and plant water status were reduced in stressed plants, with young leaves significantly more affected than fully-expanded leaves beginning from the 5th day of drought stress. A. chilensis plants increased their ABA and total anthocyanin content and showed upregulation of gene expression when they were subjected to severe drought (day 20), with these effects being higher in fully-expanded leaves. Multivariate analysis indicated a significant positive correlation between transcript levels for NCED1 (9-cis-epoxycarotenoid dioxygenase) and UFGT (UDP glucose: flavonoid-3-O-glucosyltransferase) with ABA and total anthocyanin, respectively. Thus, this research provides a more comprehensive analysis of the mechanisms that allow plants to cope with drought stress. This is highlighted by the differences between young and fully-expanded leaves, showing different sensibility to stress due to their ability to synthesize anthocyanins. In addition, this ability to synthesize different and high amounts of anthocyanins could be related to higher NCED1 and MYB expression and ABA levels, enhancing drought stress tolerance.

Stress-induced changes of growth, yield and bioactive compounds in lemon balm cultivars

The aim of the present study was to investigate the impact of water deficiency on five Melissa officinalis genotypes. For three months water supply of 70% (control) and 40% (stress) of soil water capacity treatments have been adjusted in a pot experiment. Considering the morphological data, the different genetic potentials of cultivars were manifested only under optimum water regimes while under drought they merged into one homogeneous basic population representing the species. The biomass data decreased for all cultivars under drought stress, but the degree of loss was genotype specific. Genotype dependence of the change in essential oil accumulation was clearly proved by the data. Three of the cultivars ('Gold Leaf', 'Lorelei' and 'Quedlinburger Niederliegende') showed the same essential oil content both in control and stress treatments. Under drought stress the cultivar 'Lemona' produced only 35% of its essential oil content, however cv. 'Soroksár' reacted with 58% increase of essential oil accumulation to drought treatment. Considering the non-volatile bioactive compounds a unique response of the investigated accessions to drought stress was demonstrated. Cultivar 'Lorelei' showed an increased accumulation of total hydroxicinnamic acid derivatives content while cv. 'Gold Leaf' and 'Soroksár' clearly reacted with higher accumulation of total flavonoid fraction. In the case of cv. 'Quedlinburger Niederliegende' the remarkable decline in total flavonoid content is the most obvious stress reaction. The rosmarinic acid content of all genotypes showed lower accumulation level in consequence of lower water supply.

Pyramiding of tea Dihydroflavonol reductase and Anthocyanidin reductase increases flavan-3-ols and improves protective ability under stress conditions in tobacco

Tea (Camellia sinensis) is one of the richest sources of flavan-3-ols, an important class of flavonoids. The expression level of gene-encoded key regulatory enzymes of flavan-3-ol/anthocyanin biosynthetic pathway, dihydroflavonol 4-reductase (DFR) and anthocyanidin reductase (ANR), has been highly correlated with the flavan-3-ol contents and antioxidant activity in tea plant. In the present study, pyramiding of CsDFR and CsANR in tobacco was achieved. However, single transgenic tobacco overexpressing either CsDFR or CsANR was documented earlier. In continuation, pyramided transgenic lines were evaluated for the possible, either same or beyond, effect on flavan-3-ol accumulation and protective ability against biotic and abiotic stresses. The pyramided transgenic lines showed early flowering and improved seed yield. The transcript levels of flavan-3-ol/anthocyanin biosynthetic pathway and related genes in pyramided transgenic lines were upregulated as compared to control tobacco plants. The accumulations of flavan-3-ols were also found to be higher in pyramided transgenic lines than control tobacco plants. In contrast, anthocyanin content was observed to be decreased in pyramided transgenic lines, while DPPH activity was higher in pyramided transgenic lines. In pyramided transgenic lines, strong protective ability against feeding by Spodoptera litura was documented. The seeds of pyramided transgenic lines were also found to have better germination rate under aluminum toxicity as compared to control tobacco plants. Interestingly, the synergistic effect of these two selected genes are not beyond from transgenic lines expressing either CsDFR and CsANR alone as published earlier in terms of flavan-3-ols accumulation. However, the unique flower color and better seed germination rate are some interestingly comparable differences that were reported in pyramided lines in relation to individual transgenic plants. In conclusion, the present results reveal an interesting dynamic between CsDFR and CsANR in modulating flavan-3-ol/anthocyanin levels and functional analysis of stacked CsDFR and CsANR transgenic tobacco lines.

UPLC-QTOF analysis reveals metabolomic changes in the flag leaf of wheat (Triticum aestivum L.) under low-nitrogen stress

Wheat is one of the most important grain crop plants worldwide. Nitrogen (N) is an essential macronutrient for the growth and development of wheat and exerts a marked influence on its metabolites. To investigate the influence of low nitrogen stress on various metabolites of the flag leaf of wheat (Triticum aestivum L.), a metabolomic analysis of two wheat cultivars under different induced nitrogen levels was conducted during two important growth periods based on large-scale untargeted metabolomic analysis using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF). Multivariate analyses-such as principle components analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA)-were used for data analysis. PCA yielded distinctive clustering information among the samples, classifying the wheat flag samples into two categories: those under normal N treatment and low N treatment. By processing OPLS-DA, eleven secondary metabolites were shown to be responsible for classifying the two groups. The secondary metabolites may be considered potential biomarkers of low nitrogen stress. Chemical analyses showed that most of the identified secondary metabolites were flavonoids and their related derivatives, such as iso-vitexin, iso-orientin and methylisoorientin-2″-O-rhamnoside, etc. This study confirmed the effect of low nitrogen stress on the metabolism of wheat, and revealed that the accumulation of secondary metabolites is a response to abiotic stresses. Meanwhile, we aimed to identify markers which could be used to monitor the nitrogen status of wheat crops, presumably to guide appropriate fertilization regimens. Furthermore, the UPLC-QTOF metabolic platform technology can be used to study metabolomic variations of wheat under abiotic stresses.

Transcriptome Analysis of Salicylic Acid Treatment in Rehmannia glutinosa Hairy Roots Using RNA-seq Technique for Identification of Genes Involved in Acteoside Biosynthesis

Rehmannia glutinosa is a common bulk medicinal material that has been widely used in China due to its active ingredients. Acteoside, one of the ingredients, has antioxidant, antinephritic, anti-inflammatory, hepatoprotective, immunomodulatory, and neuroprotective effects, is usually selected as a quality-control component for R. glutinosa herb in the Chinese Pharmacopeia. The acteoside biosynthesis pathway in R. glutinosa has not yet been clearly established. Herein, we describe the establishment of a genetic transformation system for R. glutinosa mediated by Agrobacterium rhizogenes. We screened the optimal elicitors that markedly increased acteoside accumulation in R. glutinosa hairy roots. We found that acteoside accumulation dramatically increased with the addition of salicylic acid (SA); the optimal SA dose was 25 μmol/L for hairy roots. RNA-seq was applied to analyze the transcriptomic changes in hairy roots treated with SA for 24 h in comparison with an untreated control. A total of 3,716, 4,018, and 2,715 differentially expressed transcripts (DETs) were identified in 0 h-vs.-12 h, 0 h-vs.-24 h, and 12 h-vs.-24 h libraries, respectively. KEGG pathway-based analysis revealed that 127 DETs were enriched in "phenylpropanoid biosynthesis." Of 219 putative unigenes involved in acteoside biosynthesis, 54 were found to be up-regulated at at least one of the time points after SA treatment. Selected candidate genes were analyzed by quantitative real-time PCR (qRT-PCR) in hairy roots with SA, methyl jasmonate (MeJA), AgNO₃ (Ag⁺), and putrescine (Put) treatment. All genes investigated were up-regulated by SA treatment, and most candidate genes were weakly increased by MeJA to some degree. Furthermore, transcription abundance of eight candidate genes in tuberous roots of the high-acteoside-content (HA) cultivar QH were higher than those of the low-acteoside-content (LA) cultivar Wen 85-5. These results will pave the way for understanding the molecular basis of acteoside biosynthesis in R. glutinosa, and can serve as a basis for future validation studies.

H2O2 Improves Quality of Radix scutellariae Through Anti-oxidant Effect

Introduction:

The correlation between the quality and geographical origin of herbal medicine was traced back to Tang Dynasty in China, more than 1200 years, and the effects of ecological environments on the secondary metabolites such as flavonoids have been confirmed. However, little is known about how the adversity impacts on the quality. Reactive oxygen species (ROS) may be medium between the ecological environment and the secondary metabolism.

Materials and Methods:

The fresh roots of Scutellaria baicalensis Georgi were treated with 0.002 μmol/L, 0.2 μmol/L, and 20 μmol/L H₂O₂, respectively. A stress model was established to elucidate the change of secondary metabolism, anti-oxidant enzyme system, and enzymes relating to flavonoids.

Results:

The activities of superoxide dismutase, catalase and peroxidase decreased. Too much H₂O₂, firstly, boosted transformation of flavonoids glycoside into aglucon with the most remarkable activities through UDP-glucuronate baicalein 7-O-glucuronosyltransferase (UBGAT), and β-glucuronidase (GUS), then regulated the gene expression of phenylalanine ammonialyase, GUS, and UBGAT, and increased the contents of flavones, motivated the flavonoid glycoside converting into aglucon. With this action, the flavones displaced the anti-oxidant enzymes. The higher the dosage, the more baicalein and wogonin increased, the later they took action.

Conclusion:

The plant secondary metabolites to keep ROS constant are identical to the effective materials in clinic. They are closely linked. H₂O₂ can improve flavones, especially the aglucon, and further increased the quality of herbal medicine, which possesses very important value in medical practice.

SUMMARY

H₂O₂ decreasing the activities of CAT and POD lead to accumulation of more H₂O₂. Excess of H₂O₂ up-regulated PAL, BUG, promote biosynthesis of flavones, and enhance the nonenzyme system. “↑” and “↓” represent activity or content “up” and “down” respectively.

Sodium dithionite-enhanced quality of radix scutellariae through modification of secondary metabolism

Introduction:

The quality of radix scutellariae is particularly associated with environmental stresses, but detailed mechanisms remained unclear. Plant under unfavorable situation generates redundant reactive oxygen species (ROS), and ROS can modify the secondary metabolism. The varied quality of radix scutellariae could be explained by ROS.

Materials and Methods:

.004, 0.4, and 40 μmol/L of sodium dithionite (Na₂S₂O₄), a material producing ROS, were applied to Scutellaria baicalensis to mimic unfavorable situation. The relationship between ROS, antioxidant enzymes activity, and secondary metabolite was investigated.

Results:

ROS level fails to rise due to both the antioxidase and the secondary metabolites. The activities of both superoxide dismutase and catalase in the roots of S. baicalensis showed a moderately improvement, meanwhile the phenylalanine ammonia lyase was strongly expressed, and the biosynthesis of flavonoids was heavily elevated. Although the glycosides such as baicalin and wogonoside changed little, the aglycones with the highest effective, such as baicalein and wogonin, were increased by approximately 50%-100%.

Conclusion:

This is very valuable in insight into the stress physiology and provides a strong tool to enhance the quality of radix scutellariae.

Micropropagation of Agave salmiana: Means to Production of Antioxidant and Bioactive Principles

Maguey, Agave salmiana, is an important plant for the "pulque" beverage and functional food industries; however, it has several constraints for elite and homogeneous plant production. In this study, a micropropagation process was established to generate in vitro plants. The effect of the method on metabolite content and antioxidant (AOX) activity in regenerated plants was evaluated. Young germinated plantlets were micropropagated from axillary shoots using Murashige and Skoog medium supplemented with L2 vitamins, 0.04 mg/L 2,4-dichlorophenoxyacetic acid and 10 mg/L 6-benzylaminopurine. Total soluble sugars from the aqueous fraction and total phenolic acids, total saponins, and AOX activity of the methanol fraction were determined in wild-type (WT) plants, in in vitro (IN) plants, and ex vitro acclimated plants (EN). The results showed that IN plants have a 50% lower soluble sugar content compared to WT, and EN. The total phenolic acids content was at least 30% higher in micropropagated (IN) and regenerated (EN) plants compared to WT. The total saponin content in IN, and EN plants was 36 and 25 times higher compared to WT. The AOX capacity of IN plants was on average three times higher compared to other treatments. However, no correlation was found between the AOX activity and total phenolic acids or total saponins. A negative and significant correlation (r = -0.927; p = 0.003) was found between the AOX activity and the total soluble sugars content. Micropropagated plants of A. salmiana have a different phytochemical content and bioactivity after the in vitro process compared to WT plants. The micropropagation process could be used as a platform for phytochemical enhancement of Agave plants.

Molecular characterization and functional analysis of barley semi-dwarf mutant Riso no. 9265

Background

sdw1/denso is one of the most important and useful semi-dwarf genes in barley breeding. At least four sdw1/denso alleles have been reported and HvGA20ox₂ is considered as the candidate gene. Up to date, results of studies have not univocally proven the genetic relationship between sdw1/denso and HvGA20ox₂.

Results

In the present study, a complete deletion of Morex_contig_40861 including both HvGA20ox₂ and Mloc_56463 genes was identified at the sdw1 locus from a semi-dwarf mutant Riso no. 9265. Expression of the genes encoding gibberellin biosynthesis (HvGA20ox₁ and HvGA3ox₂) were increased in the mutant compared to the wild type Bomi, while the expression of GA catabolic gene HvGA2ox₃ was decreased. Over-expression of HvGA20ox₂ could rescue the semi-dwarf phenotype and increase GAs concentration.

Conclusions

We confirmed that a GA biosynthetic enzyme HvGA20ox₂, acted as GA 20-oxidase, is the functional gene for the sdw1/denso semi-dwarfism. Lose of HvGA20ox₂ is partially compensated by HvGA20ox₁ and further feedback is regulated by gibberellin. We also deduced that the sdw1/denso allele itself affects later heading owing to its reduced endogenous GAs concentration.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2116-x) contains supplementary material, which is available to authorized users.

Overexpression of two R2R3-MYB genes from Scutellaria baicalensis induces phenylpropanoid accumulation and enhances oxidative stress resistance in transgenic tobacco

MYB proteins are involved in many significant physiological and biochemical processes, including regulation of primary and secondary metabolism, flavonoid biosynthesis, response to various biotic and abiotic stresses, hormone synthesis and signal transduction. The functions of R2R3-MYB proteins in Scutellaria baicalensis Georgi under abiotic stress, however, has not been elucidated. To study the molecular mechanism by which MYB2 and MYB7 respond to abiotic stress in S. baicalensis, we analyzed the phenylpropanoid content, growth phenotype, antioxidant enzyme activity and flavonoid synthesis-associated gene expression in SbMYB2 or SbMYB7-overexpressing transgenic tobacco plants after treatment with NaCl, mannitol and abscisic acid (ABA). The transgenic tobacco showed a higher fresh weight than did the wild type (WT) tobacco. In contrast, antioxidant enzyme activity and flavonoid synthesis-related gene expression were markedly higher in WT tobacco after treatment with NaCl, mannitol and ABA, as compared to transgenic plants, This is likely because increased phenylpropanoid accumulation in transgenic tobacco plants played a central role in abiotic stress resistance. These results indicate that overexpression of SbMYB2 or SbMYB7 increased phenylpropanoid accumulation and enhanced NaCl, mannitol and ABA stresses tolerance in transgenic tobacco.

Expression of flavonoid biosynthesis genes and accumulation of flavonoid in wheat leaves in response to drought stress

Flavonoids are the low molecular weight polyphenolic secondary metabolic compounds, and have various functions in growth, development, reproduction, and stress defense. However, little is known about the roles of the key enzymes in the flavonoids biosynthesis pathway in response to drought stress in winter wheat. Here, we investigated the expression pattern of flavonoids biosynthesis genes and accumulation of flavonoids in wheat leaves under drought stress. Quantitative real-time PCR analysis showed that there were a rapid increase in expression levels of TaCHS, TaCHI, TaF3H, TaFNS, TaFLS, TaDFR, and TaANS under drought stress in two wheat cultivars Aikang 58 (AK) and Chinese Spring (CS). The cultivar CS exhibited higher genes expression levels of TaCHS, TaCHI, TaF3H, TaFLS, TaDFR, and TaANS, and the cultivar AK showed a higher expression level of TaFNS gene during drought treatment. The increase rates of genes expression were superior in AK compared to CS. Total phenolics content, total flavonoids content, anthocyanin content, and schaftoside content in wheat leaves were enhanced during drought treatment and cultivar CS had a relative higher accumulation. These results suggest that the flavonoids pathway genes expression and accumulation of flavonoids compounds may be closely related to drought tolerant in wheat. Further, flavonoids response mechanism may be different between wheat cultivars.

Ragweed (Ambrosia artemisiifolia) pollen allergenicity: SuperSAGE transcriptomic analysis upon elevated CO2 and drought stress

BACKGROUND

Pollen of common ragweed (Ambrosia artemisiifolia) is a main cause of allergic diseases in Northern America. The weed has recently become spreading as a neophyte in Europe, while climate change may also affect the growth of the plant and additionally may also influence pollen allergenicity. To gain better insight in the molecular mechanisms in the development of ragweed pollen and its allergenic proteins under global change scenarios, we generated SuperSAGE libraries to identify differentially expressed transcripts.

RESULTS

Ragweed plants were grown in a greenhouse under 380 ppm CO2 and under elevated level of CO2 (700 ppm). In addition, drought experiments under both CO2 concentrations were performed. The pollen viability was not altered under elevated CO2, whereas drought stress decreased its viability. Increased levels of individual flavonoid metabolites were found under elevated CO2 and/or drought. Total RNA was isolated from ragweed pollen, exposed to the four mentioned scenarios and four SuperSAGE libraries were constructed. The library dataset included 236,942 unique sequences, showing overlapping as well as clear differently expressed sequence tags (ESTs). The analysis targeted ESTs known in Ambrosia, as well as in pollen of other plants. Among the identified ESTs, those encoding allergenic ragweed proteins (Amb a) increased under elevated CO2 and drought stress. In addition, ESTs encoding allergenic proteins in other plants were also identified.

CONCLUSIONS

The analysis of changes in the transcriptome of ragweed pollen upon CO2 and drought stress using SuperSAGE indicates that under global change scenarios the pollen transcriptome was altered, and impacts the allergenic potential of ragweed pollen.

The Scutellaria baicalensis R2R3-MYB transcription factors modulates flavonoid biosynthesis by regulating GA metabolism in transgenic tobacco plants

R2R3-MYB proteins play role in plant development, response to biotic and abiotic stress, and regulation of primary and secondary metabolism. Little is known about the R2R3-MYB proteins in Scutellaria baicalensis which is an important Chinese medical plant. In this paper, nineteen putative SbMYB genes were identified from a S. baicalensis cDNA library, and eleven R2R3-MYBs were clustered into 5 subgroups according to phylogenetic reconstruction. In the S. baicalensis leaves which were sprayed with GA3, SbMYB2 and SbMYB7 had similar expression pattern with SbPALs, indicating that SbMYB2 and SbMYB7 might be involved in the flavonoid metabolism. Transactivation assay results showed that SbMYB2 and SbMYB7 can function as transcriptional activator. The expression of several flavonoid biosynthesis-related genes were induced or suppressed by overexpression of SbMYB2 or SbMYB7 in transgenic tobacco plants. Consistent with the change of the expression of NtDH29 and NtCHI, the contents of dicaffeoylspermidine and quercetin-3,7-O-diglucoside in SbMYB2-overexpressing or SbMYB7-overexpressing transgenic tobacco plants were decreased. The transcriptional level of NtUFGT in transgenic tobacco overexpressing SbMYB7 and the transcriptional level of NtHCT in SbMYB2-overexpressing tobacco plants were increased; however the application of GA3 inhibited the transcriptional level of these two genes. These results suggest that SbMYB2 and SbMYB7 might regulate the flavonoid biosynthesis through GA metabolism.

Cytokinin-induced parthenocarpic fruit development in tomato is partly dependent on enhanced gibberellin and auxin biosynthesis

Fruit set of plants largely depends on the biosynthesis and crosstalk of phytohormones. To date the role of cytokinins (CKs) in the fruit development is less understood. Here, we showed that parthenocarpic fruit could be induced by 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU, an active CK) in tomato (Solanumlycopersicum cv. Micro-Tom). The fresh weight of CPPU-induced parthenocarpic fruits was comparable with that induced by GA3. Importantly, CPPU-induced parthenocarpy was found to be compromised by simultaneous application of paclobutrazol (a GA biosynthesis inhibitor), and this effect could be restored by exogenous GA3. Like pollination, CPPU-induced fruit showed enhanced accumulation of GA1+3 and indole-3-acetic (IAA), which were accompanied by elevated expression of GA biosynthesis genes like SlGPS, SlGA20ox1, SlGA20ox2 and SlGA3ox1, and IAA biosynthesis gene ToFZY. Elevated GAs level in CPPU-induced fruits was also associated with down-regulation of GA inactivation genes, namely SlGA2ox1,2,3,4,5 in comparison with untreated control. These results suggested that CKs may induce parthenocarpy in tomato partially through modulation of GA and IAA metabolisms.

Transgenic Tobacco Overexpressing Tea cDNA Encoding Dihydroflavonol 4-Reductase and Anthocyanidin Reductase Induces Early Flowering and Provides Biotic Stress Tolerance

Flavan-3-ols contribute significantly to flavonoid content of tea (Camellia sinensis L.). Dihydroflavonol 4-reductase (DFR) and anthocyanidin reductase (ANR) are known to be key regulatory enzymes of flavan-3-ols biosynthesis. In this study, we have generated the transgenic tobacco overexpressing individually tea cDNA CsDFR and CsANR encoding for DFR and ANR to evaluate their influence on developmental and protective abilities of plant against biotic stress. The transgenic lines of CsDFR and CsANR produced early flowering and better seed yield. Both types of transgenic tobacco showed higher content of flavonoids than control. Flavan-3-ols such as catechin, epicatechin and epicatechingallate were found to be increased in transgenic lines. The free radical scavenging activity of CsDFR and CsANR transgenic lines was improved. Oxidative stress was observed to induce lesser cell death in transgenic lines compared to control tobacco plants. Transgenic tobacco overexpressing CsDFR and CsANR also showed resistance against infestation by a tobacco leaf cutworm Spodoptera litura. Results suggested that the overexpression of CsDFR and CsANR cDNA in tobacco has improved flavonoids content and antioxidant potential. These attributes in transgenic tobacco have ultimately improved their growth and development, and biotic stress tolerance.

Global analysis of ankyrin repeat domain C3HC4-type RING finger gene family in plants

Ankyrin repeat (ANK) C3HC4-type RING finger (RF) genes comprise a large family in plants and play important roles in various physiological processes of plant life. In this study, we identified 187 ANK C3HC4-type RF proteins from 29 species with complete genomes and named the ANK C3HC4-type RF proteins the XB3-like proteins because they are structurally related to the rice (Oryza sativa) XB3. A phylogenetic relationship analysis suggested that the XB3-like genes originated from ferns, and the encoded proteins fell into 3 major groups. Among these groups, we found that the spacing between the metal ligand position 6 and 7, and the conserved residues, which was in addition to the metal ligand amino acids, in the C3HC4-type RF were different. Using a wide range of protein structural analyses, protein models were established, and all XB3-like proteins were found to contain two to seven ANKs and a C3HC4-type RF. The microarray data for the XB3-like genes of Arabidopsis, Oryza sative, Zea mays and Glycine max revealed that the expression of XB3-like genes was in different tissues and during different life stages. The preferential expression of XB3-like genes in specified tissues and the response to phytohormone and abiotic stress treatments of Arabidopsis and Zea mays not only confirmed the microarray analysis data but also demonstrated that the XB3-like proteins play roles in plant growth and development as well as in stress responses. Our data provide a very useful reference for the identification and functional analysis of members of this gene family and also provide a new method for the genome-wide analysis of gene families.