Accumulation Of Flavonoids Research Articles

CcCHIL, a type IV chalcone isomerase that can improve (2S)-naringenin production in Saccharomyces cerevisiae

(2S)-Naringenin, a crucial precursor in plant flavonoid synthesis, holds significance in diverse biological processes and potential therapeutic applications for human diseases. The economically valuable Citrus reticulata 'Chachi' citrus cultivar, renowned for its flavonoid-rich peel, was subjected to integrated transcriptomic and metabolomic analysis in this study to reveal patterns of flavonoid accumulation. The analysis revealed a strong correlation between the expression pattern of the gene encoding type IV chalcone isomerase (chalcone isomerase like, CHIL), CcCHIL, and the accumulation of flavonoids in C. reticulata 'Chachi' peel. Previous studies have demonstrated that type IV chalcone isomerase can enhance flavonoid accumulation in citrus and improve the catalytic efficiency of chalcone synthase in vitro, thereby increasing the titer of (2S)-naringenin. In this study, we constructed a genetically engineered yeast strain capable of de novo synthesis of (2S)-naringenin. We found that CcCHIL can increase (2S)-naringenin production in engineered yeast by 13.60 %. Subsequently, we conducted experiments using CHILs from various species and found that GmCHIL from Glycine max can increase (2S)-naringenin production in engineered yeast by 45.35 %. Sequence alignment, molecular docking predictions and site-directed mutagenesis showed that Asn151 is one of the key sites for CHIL improving (2S)-naringenin production. Our study unveiled CcCHIL's crucial role in flavonoid biosynthesis in C. reticulata 'Chachi' peel and paving the way for future synthesis of intricate and economically valuable flavonoids.

Flavonoid Synthesis Pathway Response to Low-Temperature Stress in a Desert Medicinal Plant, Agriophyllum Squarrosum (Sandrice).

Background/Objectives:Agriophyllum squarrosum (L.) Moq. (A. squarrosum), also known as sandrice, is an important medicinal plant widely distributed in dunes across all the deserts of China. Common garden trials have shown content variations in flavonoids among the ecotypes of sandrice, which correlated with temperature heterogeneity in situ. However, there have not been any environmental control experiments to further elucidate whether the accumulation of flavonoids was triggered by cold stress; Methods: This study conducted a four-day ambient 4 °C low-temperature treatment on three ecotypes along with an in situ annual mean temperature gradient (Dulan (DL), Aerxiang (AEX), and Dengkou (DK)); Results: Target metabolomics showed that 12 out of 14 flavonoids in sandrice were driven by cold stress. Among them, several flavonoids were significantly up-regulated, such as naringenin and naringenin chalcone in all three ecotypes; isorhamnetin, quercetin, dihydroquercetin, and kaempferol in DL and AEX; and astragalin in DK. They were accompanied by 19 structural genes of flavonoid synthesis and 33 transcription factors were markedly triggered by cold stress in sandrice. The upstream genes, AsqAEX006535-CHS, AsqAEX016074-C4H, and AsqAEX004011-4CL, were highly correlated with the enrichment of naringenin, which could be fine-tuned by AsqAEX015868-bHLH62, AsqAEX001711-MYB12, and AsqAEX002220-MYB1R1; Conclusions: This study sheds light on how desert plants like sandrice adapt to cold stress by relying on a unique flavonoid biosynthesis mechanism that regulating the accumulation of naringenin. It also supports the precise development of sandrice for the medicinal industry. Specifically, quercetin and isorhamnetin should be targeted for development in DL and AEX, while astragalin should be precisely developed in DK.

Systematic Identification and Characterization of O-Methyltransferase Gene Family Members Involved in Flavonoid Biosynthesis in Chrysanthemum indicum L.

Chrysanthemum indicum L. capitulum is an enriched source of flavonoids with broad-ranging biological activities, mainly due to their anti-inflammatory, anti-cancer, immune regulation, anti-microbial activity, hepatoprotective, and neuroprotective effects. The O-methylation of various secondary metabolites has previously been demonstrated to be mainly catalyzed by S-adenosyl-L-methionine-dependent O-methyltransferase (OMT) proteins encoded by the OMT gene family. However, limited comprehensive study was published on the OMT gene family, especially the CCoAOMT subfamily, involved in the O-methylation of flavonoids in Chrysanthemum. Here, we analyzed the spatiotemporal expression patterns of C. indicum OMT genes in leaf and flower at different developmental stages. Transcriptome sequencing and qRT-PCR analysis showed that COMTs were mainly highly expressed in capitulum, especially in full bloom, while CCoAOMTs were mainly highly expressed in leaves. Correlation analysis of OMT gene expression and flavonoids accumulation revealed that four OMTs (CHR00029120, CHR00029783, CHR00077404, and CHR00078333) were putatively involved in most methylated flavonoids biosynthesis in the capitulum. Furthermore, we identified a true CCoAOMT enzyme, CiCCoAOMT1, and found that it catalyzed O-methylation of quercetin and luteolin at the 3'-OH position. In summary, this work provides an important theoretical basis for further research on the biological functions of OMTs in C. indicum.

Exogenous methyl jasmonate induces CHS and promotes flavonoid accumulation in Zanthoxylum bungeanum

Methyl jasmonate (MeJA) is widely involved in the life processes of plants, especially playing an active role in regulating the synthesis and accumulation of metabolites. Prickly ash (Zanthoxylum bungeanum), as a species of spice tree, is rich in flavonoids throughout its entire plant, showing enormous potential for development into functional foods. Flavonoids play crucial roles in signal transduction and defense mechanisms between plants and their environment, influencing the ecological adaptability of plants. Analyzing the regulatory relationship between methyl jasmonate and flavonoid metabolites will help understand the self-protection mechanism of Zanthoxylum bungeanum under adverse stress. Research results show that the upstream promoter of CHSs (Chalcone synthase), a key gene for flavonoid synthesis, contains multiple methyl jasmonate response elements. Exogenous MeJA induction experiments proved that MeJA can significantly increase the expression levels of ZbCHS71, ZbCHS43 and ZbCHS26 in different tissues of Zanthoxylum bungeanum and directly promote the synthesis and accumulation of flavonoid metabolites. The research results help analyze the regulatory relationship between methyl jasmonate and flavonoids, and provide a reference for research on the accumulation of protective substances under stress conditions in Zanthoxylum bungeanum.

Morphological, physiological, and biochemical responses of three different soybean (Glycine max L.) varieties under salinity stress conditions.

Salinity is one of the most detrimental factors for the growth performance and productivity of crops worldwide. Therefore, understanding crop responses or growth potentials and their effectiveness in salinity mitigation is highly important for the selection of salinity-tolerant plant varieties. In this study, the effects of salinity at various stress levels (0 mM, 50 mM, 100 mM, and 150 mM NaCl) on the morphological, physiological, and biochemical parameters of three soybean varieties ('Afigat', 'Gishama', and 'Pawi-2') were investigated. The results showed that salinity significantly reduced morphological traits including plant height, number of leaves per plant, stem thickness, shoot and root length, and fresh and dry weight. This reduction was more prominent in the 'Afigat' variety for all of these traits except shoot and root length. The concentrations of chlorophyll a and b decreased with increasing salinity. In addition, salinity significantly increased leaf electrolyte leakage (EL), lipid peroxidation, proline accumulation, and phenol and flavonoid content. The 'Pawi-2' variety was more tolerant than the other studied varieties in terms of membrane stability (less EL and a low malondialdehyde content) and proline, phenol, and flavonoid accumulation. Therefore, 'Pawi-2' may be considered as the most salt-tolerant variety in comparison with the other studied soybean varieties. Further complementary studies in field conditions including anatomical parameters are needed to confirm these findings.

Multi-omics analysis reveals the transcription factor AtuMYB306 improves drought tolerance by regulating flavonoid metabolism in Chinese chive (Allium tuberosum Rottler)

Drought is one of the most detrimental stresses that severely constrains plant growth and productivity. Although Chinese chive (Allium tuberosum Rottler) is a vegetable species that is cultivated and consumed worldwide, few studies have investigated how this species responds to drought. In this study, we conducted transcriptomics, metabolomics, and proteomics analyses on chive seedlings exposed to different water availability conditions (mild drought, moderate drought, severe drought, and re-watering) and found that the accumulation of flavonoids in chive leaves was substantially altered under drought stress. Gene co-expression regulatory network analysis, conducted by integrating transcriptome and metabolome data, revealed a chive R2R3-MYB transcription factor, AtuMYB306, as a central regulator of flavonoid synthesis. Overexpression of AtuMYB306 significantly improved osmotic stress tolerance and enhanced flavonoid content in Arabidopsis. We further demonstrated that AtuMYB306 directly binds to the promoters of three flavonoid biosynthetic genes (Atu4CL, AtuF3H, and AtuF3’H) and activates their expression. These results suggest that AtuMYB306 improves drought tolerance in Chinese chive by enhancing flavonoid biosynthesis to scavenge reactive oxygen species (ROS) generated under water-deficit conditions. Thus, our findings provide evidence that AtuMYB306 playing a pivotal role in improving drought resistance in Chinese chive.

A 3R-MYB transcription factor is involved in Methyl Jasmonate-Induced disease resistance in Agaricus bisporus and has implications for disease resistance in Arabidopsis

IntroductionMethyl jasmonate (MeJA) and MYB transcription factors (TFs) play important roles in pathogen resistance in several plants, but MYB TFs in conjunction with MeJA-induced defense against Pseudomonas tolaasii in edible mushrooms remain unknown. ObjectivesTo investigate the role of a novel 3R-MYB transcription factor (AbMYB11) in MeJA-induced disease resistance of Agaricus bisporus and in the resistance of transgenic Arabidopsis to P. tolaasii. MethodsMushrooms were treated with MeJA alone or in combination with phenylpropanoid pathway inhibitors, and the effects of the treatments on the disease-related and physiological indicators of the mushrooms were determined to assess the role of MeJA in inducing resistance and the importance of the phenylpropanoid pathway involved. Subcellular localization, gene expression analysis, dual-luciferase reporter assay, electrophoretic mobility shift assay, and transgenic Arabidopsis experiments were performed to elucidate the molecular mechanism of AbMYB11 in regulating disease resistance. ResultsMeJA application greatly improved mushroom resistance to P. tolaasii infection, and suppression of the phenylpropanoid pathway significantly weakened this effect. MeJA treatment stimulated the accumulation of phenylpropanoid metabolites, which was accompanied by increased the activities of biosynthetic enzymes and the expression of phenylpropanoid pathway-related genes (AbPAL1, Ab4CL1, AbC4H1) and an AbPR-like gene, further confirming the critical role of the phenylpropanoid pathway in MeJA-induced responses to P. tolaasii. Importantly, AbMYB11, localized in the nucleus, was rapidly induced by MeJA treatment under P. tolaasii infection; it transcriptionally activated the phenylpropanoid pathway-related and AbPR-like genes, and AbMYB11 overexpression in Arabidopsis significantly increased the transcription of phenylpropanoid-related genes, the accumulation of total phenolics and flavonoids, and improved resistance to P. tolaasii. ConclusionThis study clarified the pivotal role of AbMYB11 as a regulator in disease resistance by modulating the phenylpropanoid pathway, providing a novel idea for the breeding of highly disease-resistant edible mushrooms and plants.

Regulation of exogenous sugars on the biosynthesis of key secondary metabolites in Cyclocarya paliurus.

The biosynthesis and accumulation of secondary metabolites play a vital role in determining the quality of medicinal plants, with carbohydrate metabolism often influencing secondary metabolism. To understand the potential regulatory mechanism, exogenous sugars (sucrose, glucose/fructose) were applied to the leaves of Cyclocarya paliurus, a highly valued and multiple function tree species. The results showed that exogenous sugars enhanced the accumulation of soluble sugar and starch while increasing the enzyme activity related to carbohydrate metabolism. In addition, the plant height was increased by a mixture of exogenous mixed sugars, the addition of sucrose promoted the net photosynthetic rate, while all types of exogenous sugars facilitated the accumulation of flavonoids and terpenoids. Based on weighted gene co-expression network analysis (WGCNA), two key gene modules and four candidate transcription factors (TFs) related to carbohydrate metabolism and secondary metabolite biosynthesis were identified. A correlation analysis between transcriptome and metabolome data showed that exogenous sugar up-regulated the expression of key structural genes in the flavonoid and terpenoid biosynthetic pathway. The expression levels of the four candidate TFs, TIFY 10A, WRKY 7, EIL 3 and RF2a, were induced by exogenous sugar and were strongly correlated with the key structural genes, which enhanced the synthesis of specific secondary metabolites and some plant hormone signal pathways. Our results provide a comprehensive understanding of key factors in the quality formation of medicinal plants and a potential approach to improve the quality.

Multi-omics reveals the metabolic changes and genetic basis of post-flowering rice caryopsis under blue light

BackgroundThe effects of blue light on photosynthetic organs have been studied. However, its effects on non-photosynthetic organs, in particular, on the early stages of rice caryopsis development, are unclear. Thus, we aimed to determine the metabolic characteristics of caryopsis development under blue light to improve the metabolic quality of crop kernels.ResultsWe conducted a multi-omics analysis of each of the three periods from the beginning of cellular differentiation to the end of morphogenesis in post-pollination seeds of a japonica rice variety to explore the effect of blue light on metabolic levels during these metabolic changes and its genetic basis. It was found that blue light caused a gradual decrease in auxin content, a significant increase in the accumulation of JA and flavonoids, and a downregulation of the expression of many starch-related genes and proteins, leads to reduced starch synthesis and smaller starch granules. In addition, the gene co-expression network identified three transcription factors that may regulate starch and two that may regulate flavonoids.ConclusionsIt was found through multi-omics testing that hormones such as jasmonic acid and auxins, and metabolites including alkaloids, flavonoids, lipids, organic acids, phenolic acids, and terpenoids altered significantly. Transcriptome and proteome analyses showed that blue light affected the seed nutrient repository activity. Specifically, starch- and gluten-related genes and proteins were significantly downregulated. Co- and WGCNA analyses identified several transcription factors that were regulated under blue light and identified key regulators of starch. Our study provides an understanding of the effects of blue light on post-flowering development in Gramineae and provides a framework for blue light-induced synthesis of secondary metabolites.Graphical

Dissecting the genetic basis of UV-B responsive metabolites in rice

BackgroundUV-B, an important environmental factor, has been shown to affect the yield and quality of rice (Oryza sativa) worldwide. However, the molecular mechanisms underlying the response to UV-B stress remain elusive in rice.ResultsWe perform comprehensive metabolic profiling of leaves from 160 diverse rice accessions under UV-B and normal light conditions using a widely targeted metabolomics approach. Our results reveal substantial differences in metabolite accumulation between the two major rice subspecies indica and japonica, especially after UV-B treatment, implying the possible role and mechanism of metabolome changes in subspecies differentiation and the stress response. We next conduct a transcriptome analysis from four representative rice varieties under UV-B stress, revealing genes from amino acid and flavonoid pathways involved in the UV-B response. We further perform a metabolite-based genome-wide association study (mGWAS), which reveals 3307 distinct loci under UV-B stress. Identification and functional validation of candidate genes show that OsMYB44 regulates tryptamine accumulation to mediate UV-B tolerance, while OsUVR8 interacts with OsMYB110 to promote flavonoid accumulation and UV-B tolerance in a coordinated manner. Additionally, haplotype analysis suggests that natural variation of OsUVR8groupA contributes to UV-B resistance in rice.ConclusionsOur study reveals the complex biochemical and genetic foundations that govern the metabolite dynamics underlying the response, tolerance, and adaptive strategies of rice to UV-B stress. These findings provide new insights into the biochemical and genetic basis of the metabolome underlying the crop response, tolerance, and adaptation to UV-B stress.

Transcriptomic and Metabolomic Analysis Reveals the Potential Roles of Polyphenols and Flavonoids in Response to Sunburn Stress in Chinese Olive (Canarium album).

Sunburn stress is one of the main environmental stress factors that seriously affects the fruit development and quality of Chinese olive, a tropical and subtropical fruit in south China. Therefore, the understanding of the changes in physiological, biochemical, metabolic, and gene expression in response to sunburn stress is of great significance for the industry and breeding of Chinese olive. In this study, the different stress degrees of Chinese olive fruits, including serious sunburn injury (SSI), mild sunburn injury (MSI), and ordinary (control check, CK) samples, were used to identify the physiological and biochemical changes and explore the differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) by using transcriptomics and metabolomics. Compared with CK, the phenotypes, antioxidant capacity, and antioxidant-related enzyme activities of sunburn stress samples changed significantly. Based on DEG-based KEGG metabolic pathway analysis of transcriptomics, the polyphenol and flavonoid-related pathways, including phenylpropanoid biosynthesis, sesquiterpenoid, and triterpenoid biosynthesis, monoterpene biosynthesis, carotenoid biosynthesis, isoflavonoid biosynthesis, flavonoid biosynthesis, were enriched under sunburn stress of Chinese olive. Meanwhile, 33 differentially accumulated polyphenols and 99 differentially accumulated flavonoids were identified using metabolomics. According to the integration of transcriptome and metabolome, 15 and 8 DEGs were predicted to regulate polyphenol and flavonoid biosynthesis in Chinese olive, including 4-coumarate-CoA ligase (4CL), cinnamoyl-CoA reductase (CCR), cinnamoyl-alcohol dehydrogenase (CAD), chalcone synthase (CHS), flavanone-3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS). Additionally, the content of total polyphenols and flavonoids was found to be significantly increased in MSI and SSI samples compared with CK. Our research suggested that the sunburn stress probably activates the transcription of the structural genes involved in polyphenol and flavonoid biosynthesis in Chinese olive fruits to affect the antioxidant capacity and increase the accumulation of polyphenols and flavonoids, thereby responding to this abiotic stress.

Integrated transcriptome and targeted metabolome analyses provide insights into flavonoid biosynthesis in kiwifruit (Actinidia chinensis)

So far, a variety of metabolite components of kiwifruit have been elucidated. However, the identification and analysis of flavonoids in different tissues of kiwifruit are rarely carried out. In this study, we performed transcriptome and metabolome analyses of roots (Gkf_R), stems (Gkf_T), leaves (Gkf_L), and fruits (Gkf_F) to provide insights into the differential accumulation and regulation mechanisms of flavonoids in kiwifruit. Results showed that a total of 301 flavonoids were identified, in four tissues with different accumulation trends, and a large proportion of flavonoids had high accumulation in Gkf_L and Gkf_R. A total of 84 genes have been identified involved in the flavonoid biosynthesis pathway, and the expression levels of five LAR, two DFR, and one HCT were significantly correlated with the accumulation of 16 flavonoids and co-localized in the flavonoid biosynthesis pathway. In addition, a total of 2362 transcription factor genes were identified, mainly MYBs, bHLHs, ERFs, bZIPs and WRKYs, among which the expression level of bHLH74, RAP2.3L/4L/10L, MYB1R1, and WRKY33 were significantly correlated with 25, 56, 43, and 24 kinds of flavonoids. Our research will enrich the metabolomic data and provide useful information for the directed genetic improvement and application in the pharmaceutical industry of kiwifruit.

Ionic titanium is expected to improve the nutritional quality of Tartary buckwheat sprouts through flavonoids and amino acid metabolism

Tartary buckwheat sprouts are highly valued by consumers for their superior nutritional content. Ionic titanium (Ti) has been shown to enhance crop growth and improve nutritional quality. However, there is limited research on the impact of ionic Ti on the nutritional quality of Tartary buckwheat sprouts. This study cultivated Tartary buckwheat sprouts with ionic Ti and found that the high concentration of ionic Ti significantly increased the contents of chlorophyll a, chlorophyll b, and carotenoids (increased by 25.5%, 27.57%, and 15.11%, respectively). The lower concentration of ionic Ti has a higher accumulation of total flavonoids and total polyphenols. Metabolomics analysis by LC-MS revealed 589 differentially expressed metabolites and 54 significantly different metabolites, enriching 82 metabolic pathways, especially including amino acid biosynthesis and flavonoid biosynthesis. This study shows that ionic Ti can promote the growth of Tartary buckwheat sprouts, improve nutritional quality, and have huge development potential in food production.

A first de novo transcriptome assembly of feijoa (Acca sellowiana [Berg] Burret) reveals key genes involved in flavonoid biosynthesis.

Acca sellowiana [Berg] Burret, a cultivated fruit tree originating from South America, is gaining the attention of the nutraceutical and pharmaceutical industries due to their high content of flavonoids and other phenolic compounds in fruits, leaves, and flowers. Flavonoids are a diverse group of secondary metabolites with antioxidant, anti-inflammatory, and antimicrobial properties. They also play a crucial role in plant immune response. Despite their importance, the lack of research on A. sellowiana genomics and transcriptomics hinders a deeper understanding of the molecular mechanisms behind flavonoid biosynthesis and its regulation. Here, we de novo assembled and benchmarked 11 A. sellowiana transcriptomes from leaves and floral tissues at three developmental stages using high-throughput sequencing. We selected and annotated the best assembly according to commonly used metrics and databases. This reference transcriptome consisted of 221,649 nonredundant transcripts, of which 107,612 were functionally annotated. We then used this reference transcriptome to explore the expression profiling of key secondary metabolite genes. Transcripts from genes involved in the flavonoid and anthocyanin biosynthesis pathways were identified. We also identified 4068 putative transcription factors, with the most abundant families being bHLH, C2H2, NAC, MYB, and MYB-related. Transcript expression profiling revealed distinct patterns of gene expression during flower development. Particularly, we found 71 differentially expressed transcripts representing 14 enzymes of the flavonoid pathway, suggesting major changes in flavonoid accumulation across floral stages. Our findings will contribute to understanding the genetic basis of flavonoids and provide a foundation for further research and exploitation of the economic potential of this species.

Canopy-Applied Benzothiadiazole (BTH) during the Pre-Harvest Period as a Tool to Increase Polyphenol Accumulation and Color Intensity in Cabernet Gernischt and Cabernet Franc

Despite the wealth of studies on benzothiadiazole (BTH) and its capacity to modulate grape polyphenol metabolism, comprehensive data detailing polyphenol accumulation at various grape growth stages remain scarce. Therefore, the present study utilized pre-harvest (at 21 days after flowering) canopy-applied BTH (50 mg/L) on Cabernet Gernischt and Cabernet Franc grapes to investigate the physicochemical and polyphenolic changes during grape maturation. The results showed that BTH treatment significantly affected the accumulation of total phenols, flavonoids, flavanols, anthocyanins, and tannins. Concurrently, it induced an increase in colorimetric parameters (CIRG, L*, b*, a*, and C*ab), resulting in the treated grapes exhibiting a greater color intensity and enhanced red-bluish colorimetric characteristics. Moreover, the BTH treatment amplified the anthocyanin content in the grapes, with the levels of petunidin-3-O-glucoside and peonidin-3-O-glucoside exhibiting remarkable increases, particularly in the Cabernet Franc grape. Notably, the content of peonidin-3-O-glucoside even surpassed that of malvidin-3-O-glucoside throughout the growth stages, indicating significant advantages in the treated samples. Additionally, the levels of flavanol, flavonols, phenolic acids, and stilbenes experienced a significant boost post-treatment. In conclusion, the application of BTH treatment can effectively enhance the accumulation of polyphenols and intensify the color of Cabernet Gernischt and Cabernet Franc grapes, thereby significantly improving the overall quality of wine grapes and ensuring the production of higher-quality wines. The research findings will serve as a theoretical foundation and provide scientific data for the appropriate utilization of BTH in wine grape cultivation.

Multiplex Approach of Metabolomic and Transcriptomic Reveals the Biosynthetic Mechanism of Light-induced Flavonoids and CGA in Chrysanthemum

Light, as an important environmental signal for plant growth and development, has been reported to be involved in the metabolism of phenylpropane. However, the light-induced phenylpropane biosynthesis mechanism in Chrysanthemum morifolium Ramat., especially flavonoid and chlorogenic acid (CGA) metabolism, is not clear. In this study, we found the flower phenotype of chrysanthemum 'HangBaiJu' became lighter after bagging. Besides, the content of main active ingredients, such as Luteolin-7-O-glucoside (Lu-7-O-G), Diosmetin-7-O-glucoside (Di-7-O-G), Apigenin-7-O-glucoside, Apigenin and CGA, was significantly decreased. Comparative transcriptome analysis (pairwise comparison, WGCNA, and k-means clustering) revealed that the expression of structural genes, such as CmPAL, CmCHS1/2, CmF3’H, CmFNS and CmHQT, was notably declined under dark conditions. Meanwhile, ‘bridge proteins’ CmMYB3/6/16 and signal transduction factors CmBBX20/22.2/22.3 were identified as key regulatory factors in the light-mediated synthesis of flavonoids and CGA in chrysanthemum. Among that, CmBBX20 could promote the accumulation of flavonoids and CGA by directly binding to the G-box core sequences of downstream target genes based on transient overexpression and Y1H assays. Overall, the preliminary molecular mechanism of BBXs and MYBs coordinately regulating the accumulation of flavonoids and CGA in chrysanthemum under different light inductions has been clarified, which provided a theoretical basis for the molecular breeding and quality improvement of chrysanthemum.

NtMYB27 acts downstream of NtBES1 to modulate flavonoids accumulation in response to UV-B radiation in tobacco.

UV-B radiation can induce the accumulation of many secondary metabolites, including flavonoids, in plants to protect them from oxidative damage. BRI1-EMS-SUPPRESSOR1 (BES1) has been shown to mediate the biosynthesis of flavonoids in response to UV-B. However, the detailed mechanism by which it acts still needs to be further elucidated. Here, we revealed that UV-B significantly inhibited the transcription of multiple transcription factor genes in tobacco, including NtMYB27, which was subsequently shown to be a repressor of flavonoids synthesis in tobacco. We further demonstrated that NtBES1 directly binds to the E-box motifs present in the promoter of NtMYB27 to mediate its transcriptional repression upon UV-B exposure. The UV-B-repressed NtMYB27 could bind to the ACCT-containing element (ACE) in the promoters of Nt4CL and NtCHS and served as a modulator that promoted the biosynthesis of lignin and chlorogenic acid (CGA) but inhibited the accumulation of flavonoids in tobacco. The expression of NtMYB27 was also significantly repressed by heat stress, suggesting its putative roles in regulating heat-induced flavonoids accumulation. Taken together, our results revealed the role of NtBES1 and NtMYB27 in regulating the synthesis of flavonoids during the plant response to UV-B radiation in tobacco.

Features of the Accumulation of Flavonoids in Medicinal Plant Raw Materials of the Synanthropic Flora of Rostov Region

Features of the Accumulation of Flavonoids in Medicinal Plant Raw Materials of the Synanthropic Flora of Rostov Region

Germination Promotes Flavonoid Accumulation of Finger Millet (Eleusine coracana L.): Response Surface Optimization and Investigation of Accumulation Mechanism.

Germination is an effective measure to regulate the accumulation of secondary metabolites in plants. In this study, we optimized the germination conditions of finger millet by response surface methodology. Meanwhile, physiological characteristics and gene expression were measured to investigate the mechanism of flavonoid accumulation in finger millet at the germination stage. The results showed that when germination time was 5.7 d, germination temperature was 31.2 °C, and light duration was 17.5 h, the flavonoid content of millet sprouts was the highest (7.0 μg/sprout). The activities and relative gene expression of key enzymes for flavonoid synthesis (phenylalanine ammonia-lyase, 4-coumarate-coenzyme a ligase, and cinnamate 4-hydroxylase) were significantly higher in finger millet sprouts germinated at 3 and 5 d compared with that in ungerminated seeds (p < 0.05). In addition, germination enhanced the activities of four antioxidant enzymes (catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase) and up-regulated the gene expression of PAL and APX. Germination increased malondialdehyde content in sprouts, which resulted in cell damage. Subsequently, the antioxidant capacity of the sprouts was enhanced through the activation of antioxidant enzymes and the up-regulation of their gene expression, as well as the synthesis of active substances, including flavonoids, total phenolics, and anthocyanins. This process served to alleviate germination-induced cellular injury. These findings provide a research basis for the regulation of finger millet germination and the enhancement of its nutritional and functional properties.

Identification of key genes involved in lignin and flavonoid accumulation during Tilia tuan seed maturation.

Transcriptomics and phenotypic data analysis identified 24 transcription factors (TFs) that play key roles in regulating the competitive accumulation of lignin and flavonoids. Tilia tuan Szyszyl. (T. tuan) is a timber tree species with important ecological and commercial value. However, its highly lignified pericarp results in a low seed germination rate and a long dormancy period. In addition, it is unknown whether there is an interaction between the biosynthesis of flavonoids and lignin as products of the phenylpropanoid pathway during seed development. To explore the molecular regulatory mechanism of lignin and flavonoid biosynthesis, T. tuan seeds were harvested at five stages (30, 60, 90, 120, and 150 days after pollination) for lignin and flavonoid analyses. The results showed that lignin accumulated rapidly in the early and middle stages (S1, S3, and S4), and rapid accumulation of flavonoids during the early and late stages (S1 and S5). High-throughput RNA sequencing analysis of developing seeds identified 50,553 transcripts, including 223 phenylpropanoid biosynthetic pathway genes involved in lignin accumulation grouped into 3 clusters, and 106 flavonoid biosynthetic pathway genes (FBPGs) grouped into 2 clusters. Subsequent WGCNA and time-ordered gene co-expression network (TO-GCN) analysis revealed that 24 TFs (e.g., TtARF2 and TtWRKY15) were involved in flavonoids and lignin biosynthesis regulation. The transcriptome data were validated by qRT-PCR to analyze the expression profiles of key enzyme-coding genes. This study revealed that there existed a competitive relationship between flavonoid and lignin biosynthesis pathway during the development of T. tuan seeds, that provide a foundation for the further exploration of molecular mechanisms underlying lignin and flavonoid accumulation in T. tuan seeds.