Regulation Of Flavonoid Biosynthesis Research Articles

Analysis of the Spatholobus suberectus full-length transcriptome identified an R2R3-MYB transcription factor-encoding gene SsMYB158 that regulates flavonoid biosynthesis

Spatholobus suberectus Dunn (Leguminosae) has been used for medicinal purposes for a long period. Flavonoids are the major bioactive components of S. suberectus. However, there is still limited knowledge of the exact method via which transcription factors (TFs) regulate flavonoid biosynthesis. The full-length transcriptome of S. suberectus was analyzed using SMRT sequencing; 61,548 transcripts were identified, including 12,311 new gene loci, 53,336 novel transcripts, 44,636 simple sequence repeats, 36,414 complete coding sequences, 871 long non-coding RNAs and 6781 TFs. The SsMYB158 TF, which is associated with flavonoid biosynthesis, belongs to the R2R3-MYB class and is localized subcellularly to the nucleus. The overexpression of SsMYB158 in Nicotiana benthamiana and the transient overexpression of SsMYB158 in S. suberectus resulted in a substantial enhancement in both flavonoids and catechin levels. In addition, there was a remarkable upregulation in the expression of essential enzyme-coding genes associated with the flavonoid biosynthesis pathways. Our study revealed SsMYB158 as a critical regulator of flavonoid biosynthesis in S. suberectus and laying the foundation for its molecular breeding.

Unveiling phenylpropanoid regulation: the role of DzMYB activator and repressor in durian (Durio zibethinus) fruit.

DzMYB2 functions as an MYB activator, while DzMYB3 acts as an MYB repressor. They bind to promoters, interact with DzbHLH1, and influence phenolic contents, revealing their roles in phenylpropanoid regulation in durian pulps. Durian fruit has a high nutritional value attributed to its enriched bioactive compounds, including phenolics, carotenoids, and vitamins. While various transcription factors (TFs) regulate phenylpropanoid biosynthesis, MYB (v-myb avian myeloblastosis viral oncogene homolog) TFs have emerged as pivotal players in regulating key genes within this pathway. This study aimed to identify additional candidate MYB TFs from the transcriptome database of the Monthong cultivar at five developmental/postharvest ripening stages. Candidate transcriptional activators were discerned among MYBs upregulated during the ripe stage based on the positive correlation observed between flavonoid biosynthetic genes and flavonoid contents in ripe durian pulps. Conversely, MYBs downregulated during the ripe stage were considered candidate repressors. This study focused on a candidate MYB activator (DzMYB2) and a candidate MYB repressor (DzMYB3) for functional characterization. LC-MS/MS analysis using Nicotiana benthamiana leaves transiently expressing DzMYB2 revealed increased phenolic compound contents compared with those in leaves expressing green fluorescence protein controls, while those transiently expressing DzMYB3 showed decreased phenolic compound contents. Furthermore, it was demonstrated that DzMYB2 controls phenylpropanoid biosynthesis in durian by regulating the promoters of various biosynthetic genes, including phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and dihydroflavonol reductase (DFR). Meanwhile, DzMYB3 regulates the promoters of PAL, 4-coumaroyl-CoA ligase (4CL), CHS, and CHI, resulting in the activation and repression of gene expression. Moreover, it was discovered that DzMYB2 and DzMYB3 could bind to another TF, DzbHLH1, in the regulation of flavonoid biosynthesis. These findings enhance our understanding of the pivotal role of MYB proteins in regulating the phenylpropanoid pathway in durian pulps.

Integrative analysis of metabolome and transcriptome reveals regulatory mechanisms of flavonoid biosynthesis in soybean under salt stress.

Salt stress is a major environmental factor that constrains soybean growth, development, and productivity. Flavonoids are key secondary metabolites that play a crucial role in enhancing plant resistance to both biotic and abiotic stress. However, a comprehensive understanding of the regulatory mechanisms underlying flavonoid biosynthesis under salt stress in soybean is lacking. In this study, an integrative analysis of soybean metabolome and transcriptome was conducted using two soybean lines, FQ03 (salt-sensitive, SS) and FQ07 (salt-tolerant, ST). A total of 650 significantly changed metabolites were identified in SS and ST after salt stress treatment. Among them, 151 flavonoids were categorized into nine classes, with flavones and flavonols being the predominant flavonoid types in soybean. Heatmap analysis showed higher contents of most flavonoid metabolites in ST than in SS under salt stress, and the total flavonoid content in ST was significantly higher than that in SS. In addition, transcriptome analysis revealed a higher number of differentially expressed genes (DEGs) in ST than in SS under salt stress. KEGG enrichment analysis revealed that DEGs were mainly enriched in pathways related to phenylpropanoid biosynthesis, isoflavonoid biosynthesis, flavonoid biosynthesis, as well as flavone and flavonol biosynthesis. Notably, 55 DEGs that were mapped to the flavonoid biosynthetic pathway were identified, with most showing higher expression levels in ST than in SS. Weighted gene correlation network analysis identified eight structural genes and six transcription factor genes as key regulators of flavonoid biosynthesis within the blue module. Furthermore, qRT-PCR results confirmed the accuracy of the transcriptomic data and reliability of the identified candidate genes. This study provides insights into the regulatory mechanisms underlying salt stress responses in soybean and highlights hub genes as potential targets for developing salt-tolerant soybean varieties.

Genome-wide profiling of WRKY genes involved in flavonoid biosynthesis in Erigeron breviscapus.

The transcription factors of WRKY genes play essential roles in plant growth, stress responses, and metabolite biosynthesis. Erigeron breviscapus, a traditional Chinese herb, is abundant in flavonoids and has been used for centuries to treat cardiovascular and cerebrovascular diseases. However, the WRKY transcription factors that regulate flavonoid biosynthesis in E. breviscapus remain unknown. In this study, a total of 75 EbWRKY transcription factors were predicted through comprehensive genome-wide characterization of E. breviscapus and the chromosomal localization of each EbWRKY gene was investigated. RNA sequencing revealed transient responses of 74 predicted EbWRKY genes to exogenous abscisic acid (ABA), salicylic acid (SA), and gibberellin 3 (GA3) after 4h of treatment. In contrast, the expression of key structural genes involved in flavonoid biosynthesis increased after 4h in GA3 treatment. However, the content of flavonoid metabolites in leaves significantly increased at 12h. The qRT-PCR results showed that the expression patterns of EbWRKY11, EbWRKY30, EbWRKY31, EbWRKY36, and EbWRKY44 transcription factors exhibited a high degree of similarity to the 11 structural genes involved in flavonoid biosynthesis. Protein-DNA interactions were performed between the key genes involved in scutellarin biosynthesis and candidate WRKYs. The result showed that F7GAT interacts with EbWRKY11, EbWRKY36, and EbWRKY44, while EbF6H has a self-activation function. This study provides comprehensive information on the regulatory control network of flavonoid accumulation mechanisms, offering valuable insights for breeding E. breviscapus varieties with enhanced scutellarin content.

The phosphorylation of a WD40-repeat protein negatively regulates flavonoid biosynthesis in Camellia sinensis under drought stress.

Flavonoids constitute the main nutraceuticals in the leaves of tea plants (Camellia sinensis). To date, although it is known that drought stress can negatively impact the biosynthesis of flavonoids in tea leaves, the mechanism behind this phenomenon is unclear. Herein, we report a protein phosphorylation mechanism that negatively regulates the biosynthesis of flavonoids in tea leaves in drought conditions. Transcriptional analysis revealed the downregulation of gene expression of flavonoid biosynthesis and the upregulation of CsMPK4a encoding a mitogen-activated protein kinase in leaves. Luciferase complementation and yeast two-hybrid assays disclosed that CsMPK4a interacted with CsWD40. Phosphorylation assay in vitro, specific protein immunity, and analysis of protein mass spectrometry indicated that Ser-216, Thr-221, and Ser-253 of CsWD40 were potential phosphorylation sites of CsMPK4a. Besides, the protein immunity analysis uncovered an increased phosphorylation level of CsWD40 in tea leaves under drought conditions. Mutation of the three phosphorylation sites generated dephosphorylated CsWD403A and phosphorylated CsWD403D variants, which were introduced into the Arabidopsis ttg1 mutant. Metabolic analysis showed that the anthocyanin and proanthocyanidin content was lower in ttg1:CsWD403D transgenic plants than ttg1::CsWD403A transgenic and wild type plants. The transient overexpression of CsWD403D downregulated the anthocyanidin biosynthesis in tea leaves. The dual-fluorescein protein complementation experiment showed that CsWD403D did not interact with CsMYB5a and CsAN2, two key transcription factors of procyanidins and anthocyanidins biosynthesis in tea plant. These findings indicate that the phosphorylation of CsWD40 by CsMPK4a downregulates the flavonoid biosynthesis in tea plants in drought stresses.

Integrative analysis of transcriptome and target metabolites uncovering flavonoid biosynthesis regulation of changing petal colors in Nymphaea ‘Feitian 2’

BackgroundNymphaea (waterlily) is known for its rich colors and role as an important aquatic ornamental plant globally. Nymphaea atrans and some hybrids, including N. ‘Feitian 2,’ are more appealing due to the gradual color change of their petals at different flower developmental stages. The petals of N. ‘Feitian 2’ gradually change color from light blue-purple to deep rose-red throughout flowering. The mechanism of the phenomenon remains unclear.ResultsIn this work, flavonoids in the petals of N. ‘Feitian 2’ at six flowering stages were examined to identify the influence of flavonoid components on flower color changes. Additionally, six cDNA libraries of N. ‘Feitian 2’ over two blooming stages were developed, and the transcriptome was sequenced to identify the molecular mechanism governing petal color changes. As a result, 18 flavonoid metabolites were identified, including five anthocyanins and 13 flavonols. Anthocyanin accumulation during flower development is the primary driver of petal color change. A total of 12 differentially expressed genes (DEGs) in the flavonoid biosynthesis pathway were uncovered, and these DEGs were significantly positively correlated with anthocyanin accumulation. Six structural genes were ultimately focused on, as their expression levels varied significantly across different flowering stages. Moreover, 104 differentially expressed transcription factors (TFs) were uncovered, and three MYBs associated with flavonoid biosynthesis were screened. The RT-qPCR results were generally aligned with high-throughput sequencing results.ConclusionsThis research offers a foundation to clarify the mechanisms underlying changes in the petal color of waterlilies.

A novel MYB transcription factor from durian (Durio zibethinus), DzMYB1, regulates flavonoid biosynthesis in fruit pulp

Flavonoids are phenolic substances and exhibit strong antioxidant properties. The biosynthesis of flavonoids is regulated by various transcription factors (TFs), with MYB TFs playing a key role in controlling essential genes within this pathway. In this study, we identified candidate MYB TFs from our pulp transcriptome database of durian ‘Monthong’ cultivar. MYBs exhibiting upregulation during the ripe stage were considered transcriptional activators, due to their positive correlation with flavonoid gene expression and flavonoid accumulation in ripe durian pulps. One candidate MYB activator, DzMYB1, which was highly expressed at the ripe stage, was selected for functional characterization. Studies involving transient expression of DzMYB1 in Solanum lycopersicum cv. Micro-Tom fruit demonstrated increased flavonoid content, as analyzed by LC–MS/MS, compared with the GFP control. Moreover, we showed that DzMYB1 controls flavonoid biosynthesis by interacting with the promoters of various flavonoid biosynthetic genes, including chalcone synthase, chalcone isomerase, and flavanone 3-hydroxylase, resulting in their transcriptional activation. Additionally, we found that DzMYB1 functions as a homodimer and binds to a homodimerized DzbHLH1 in the intricate regulation of flavonoid biosynthesis. These findings provide comprehensive insights into the functional roles of MYB protein in the regulation of the flavonoid pathway within durian pulps.

Metabolomic and transcriptomic reveal flavonoid biosynthesis and regulation mechanism in Phlomoides rotata from different habitats

Phlomoides rotata is a traditional medical plant at 3100–5200 m altitude in the Tibet Plateau. In this study, flavonoid metabolites were investigated in P. rotata from Henan County (HN), Guoluo County (GL), Yushu County (YS), and Chengduo County (CD) habitats in Qinghai. The level of kaempferol 3-neohesperidoside, sakuranetin, and biochanin A was high in HN. The content of limocitrin and isoquercetin was high in YS. The levels of ikarisoside A and chrysosplenol D in GL were high. Schaftoside, miquelianin, malvidin chloride, and glabrene in CD exhibited high levels. The results showed a significant correlation between 59 flavonoids and 29 DEGs. Eleven flavonoids increased with altitude. PAL2, UFGT6, COMT1, HCT2, 4CL4, and HCT3 genes were crucial in regulating flavonoid biosynthesis. Three enzymes CHS, 4CL, and UFGT, were crucial in regulating flavonoid biosynthesis. This study provided biological and chemical evidence for the different uses of various regional plants of P. rotata.

Biochemical and Molecular Insights into Variation in Sesame Seed Antioxidant Capability as Revealed by Metabolomics and Transcriptomics Analysis.

Sesame seeds are important resources for relieving oxidation stress-related diseases. Although a significant variation in seeds' antioxidant capability is observed, the underlying biochemical and molecular basis remains elusive. Thus, this study aimed to reveal major seed components and key molecular mechanisms that drive the variability of seeds' antioxidant activity (AOA) using a panel of 400 sesame accessions. The seeds' AOA, total flavonoid, and phenolic contents varied from 2.03 to 78.5%, 0.072 to 3.104 mg CAE/g, and 2.717 to 21.98 mg GAE/g, respectively. Analyses revealed that flavonoids and phenolic acids are the main contributors to seeds' AOA variation, irrespective of seed coat color. LC-MS-based polyphenol profiling of high (HA) and low (LA) antioxidant seeds uncovered 320 differentially accumulated phenolic compounds (DAPs), including 311 up-regulated in HA seeds. Tricin, persicoside, 5,7,4',5'-tetrahydro-3',6-dimethoxyflavone, 8-methoxyapigenin, and 6,7,8-tetrahydroxy-5-methoxyflavone were the top five up-regulated in HA. Comparative transcriptome analysis at three seed developmental stages identified 627~2357 DEGs and unveiled that differential regulation of flavonoid biosynthesis, phenylpropanoid biosynthesis, and stilbene biosynthesis were the key underlying mechanisms of seed antioxidant capacity variation. Major differentially regulated phenylpropanoid structural genes and transcription factors were identified. SINPZ0000571 (MYB), SINPZ0401118 (NAC), and SINPZ0500871 (C3H) were the most highly induced TFs in HA. Our findings may enhance quality breeding.

Integrative Analysis of Transcriptome and Metabolome Sheds Light on Flavonoid Biosynthesis in the Fruiting Body of Stropharia rugosoannulata.

Flavonoids are a diverse family of natural compounds that are widely distributed in plants and play a critical role in plant growth, development, and stress adaptation. In recent years, the biosynthesis of flavonoids in plants has been well-researched, with the successive discovery of key genes driving this process. However, the regulation of flavonoid biosynthesis in fungi remains unclear. Stropharia rugosoannulata is an edible mushroom known for its high nutritional and pharmacological value, with flavonoids being one of its main active components. To investigate the flavonoid content of S. rugosoannulata, a study was conducted to extract and determine the total flavonoids at four stages: young mushroom (Ym), gill (Gi), maturation (Ma), and parachute-opening (Po). The findings revealed a gradual increase in total flavonoid concentration as the fruiting body developed, with significant variations observed between the Ym, Gi, and Ma stages. Subsequently, we used UPLC-MS/MS and transcriptome sequencing (RNA-seq) to quantify the flavonoids and identify regulatory genes of Ym, Gi, and Ma. In total, 53 flavonoid-related metabolites and 6726 differentially expressed genes (DEGs) were identified. Through KEGG pathway enrichment analysis, we identified 59 structural genes encoding flavonoid biosynthesis-related enzymes, most of which were up-regulated during the development of the fruiting body, consistent with the accumulation of flavonoids. This research led to the establishment of a comprehensive transcriptional metabolic regulatory network encompassing flavonoids, flavonoid synthases, and transcription factors (TFs). This represents the first systematic exploration of the molecular mechanism of flavonoids in the fruiting of fungi, offering a foundation for further research on flavonoid mechanisms and the breeding of high-quality S. rugosoannulata.

Expression profiling and putative biosynthetic network of flavonoids by global analysis with simplified omics data elucidating the large potential of Akebia trifoliata as an herbal industrial plant

Akebia trifoliata has been under development as a multipurpose industrial plant for pharmaceutical, cosmetic and other biological applications, with flavonoids as the most interesting secondary metabolites. However, the accumulation dynamics and genetic regulatory network of flavonoids in A. trifoliata fruit have not been completely revealed. Here, we first annotated 258 enzyme-encoding genes (EGs) in the flavonoid biosynthetic pathway and a total of 1602 transcription factors (TFs) from the A. trifoliata reference genome, extracted the corresponding expression data from the available transcriptome data, and identified a total of 143 flavonoids, consisting of 29 aglycones and 114 derivatives, from the published metabolome. Second, we screened 54 EGs and 58 TFs by weighted gene coexpression network analysis (WGCNA) and found 11 nodal aglycones consisting of nine detected aglycones and two putative aglycones. Finally, we identified 10 key EGs and 4 key TFs based on both expression difference and expression network analysis, with four EGs (ANS1, F3H1, F3’H3 and DFR2) assigned to the subpathway of flavonoid synthesis (ko00941) and four TFs (MYB66, MYB5, bHLH71, TALE8) playing dominant regulatory roles. In conclusion, Ko00941 could be an important process regulating flavonoid biosynthesis in A. trifoliata fruit, mainly by modifying carbon rings, and DFR2 could play the most important role. In addition, A. trifoliata fruit could be an ideal system for investigating various secondary metabolites, especially at the young or ripe stage, and it could also be a new raw resource for meeting various demands for flavonoids.

Multi-omics analysis reveals the biosynthesis of flavonoids during the browning process of Malus sieversii explants.

Malus sieversii is a precious apple germplasm resource. Browning of explants is one of the most important factors limiting the survival rate of plant tissue culture. In order to explore the molecular mechanism of the browning degree of different strains of Malus sieversii, we compared the dynamic changes of Malus sieversii and Malus robusta Rehd. during the whole browning process using a multi-group method. A total of 44 048 differentially expressed genes (DEGs) were identified by transcriptome analysis on the DNBSEQ-T7 sequencing platform. KEGG enrichment analysis showed that the DEGs were significantly enriched in the flavonoid biosynthesis pathway. In addition, metabonomic analysis showed that (-)-epicatechin, astragalin, chrysin, irigenin, isoquercitrin, naringenin, neobavaisoflavone and prunin exhibited different degrees of free radical scavenging ability in the tissue culture browning process, and their accumulation in different varieties led to differences in the browning degree among varieties. Comprehensive transcriptome and metabonomics analysis of the data related to flavonoid biosynthesis showed that PAL, 4CL, F3H, CYP73A, CHS, CHI, ANS, DFR and PGT1 were the key genes for flavonoid accumulation during browning. In addition, WGCNA analysis revealed a strong correlation between the known flavonoid structure genes and the selected transcriptional genes. Protein interaction predictions demonstrated that 19 transcription factors (7 MYBs and 12 bHLHs) and 8 flavonoid structural genes had targeted relationships. The results show that the interspecific differential expression of flavonoid genes is the key influencing factor of the difference in browning degree between Malus sieversii and Malus robusta Rehd., providing a theoretical basis for further study on the regulation of flavonoid biosynthesis.

SlBEL11 regulates flavonoid biosynthesis, thus fine-tuning auxin efflux to prevent premature fruit drop in tomato.

Auxin regulates flower and fruit abscission, but how developmental signals mediate auxin transport in abscission remains unclear. Here, we reveal the role of the transcription factor BEL1-LIKE HOMEODOMAIN11 (SlBEL11) in regulating auxin transport during abscission in tomato (Solanum lycopersicum). SlBEL11 is highly expressed in the fruit abscission zone, and its expression increases during fruit development. Knockdown of SlBEL11 expression by RNA interference (RNAi) caused premature fruit drop at the breaker (Br) and 3 d post-breaker (Br+3) stages of fruit development. Transcriptome and metabolome analysis of SlBEL11-RNAi lines revealed impaired flavonoid biosynthesis and decreased levels of most flavonoids, especially quercetin, which functions as an auxin transport inhibitor. This suggested that SlBEL11 prevents premature fruit abscission by modulating auxin efflux from fruits, which is crucial for the formation of an auxin response gradient. Indeed, quercetin treatment suppressed premature fruit drop in SlBEL11-RNAi plants. DNA affinity purification sequencing (DAP-seq) analysis indicated that SlBEL11 induced expression of the transcription factor gene SlMYB111 by directly binding to its promoter. Chromatin immunoprecipitation-quantitative polymerase chain reaction and electrophoretic mobility shift assay showed that S. lycopersicum MYELOBLASTOSIS VIRAL ONCOGENE HOMOLOG111 (SlMYB111) induces the expression of the core flavonoid biosynthesis genes SlCHS1, SlCHI, SlF3H, and SlFLS by directly binding to their promoters. Our findings suggest that the SlBEL11-SlMYB111 module modulates flavonoid biosynthesis to fine-tune auxin efflux from fruits and thus maintain an auxin response gradient in the pedicel, thereby preventing premature fruit drop.

The Smi-miR858a-SmMYB module regulates tanshinone and phenolic acid biosynthesis in Salvia miltiorrhiza.

Tanshinones and phenolic acids are two major classes of bioactive compounds in Salvia miltiorrhiza. Revealing the regulatory mechanism of their biosynthesis is crucial for quality improvement of S. miltiorrhiza medicinal materials. Here we demonstrated that Smi-miR858a-Smi-miR858c, a miRNA family previously known to regulate flavonoid biosynthesis, also played critical regulatory roles in tanshinone and phenolic acid biosynthesis in S. miltiorrhiza. Overexpression of Smi-miR858a in S. miltiorrhiza plants caused significant growth retardation and tanshinone and phenolic acid reduction. Computational prediction and degradome and RNA-seq analyses revealed that Smi-miR858a could directly cleave the transcripts of SmMYB6, SmMYB97, SmMYB111, and SmMYB112. Yeast one-hybrid and transient transcriptional activity assays showed that Smi-miR858a-regulated SmMYBs, such as SmMYB6 and SmMYB112, could activate the expression of SmPAL1 and SmTAT1 involved in phenolic acid biosynthesis and SmCPS1 and SmKSL1 associated with tanshinone biosynthesis. In addition to directly activating the genes involved in bioactive compound biosynthesis pathways, SmMYB6, SmMYB97, and SmMYB112 could also activate SmAOC2, SmAOS4, and SmJMT2 involved in the biosynthesis of methyl jasmonate, a significant elicitor of plant secondary metabolism. The results suggest the existence of dual signaling pathways for the regulation of Smi-miR858a in bioactive compound biosynthesis in S. miltiorrhiza.

TON1 recruiting motif 21 positively regulates the flavonoid metabolic pathway at the translational level in Arabidopsis thaliana

Main conclusionThis study reveals that TRM21 acts as a positive regulator of flavonoid biosynthesis at the translational level in Arabidopsis, impacting both secondary metabolites and genes associated with root hair growth.TRM (TONNEAU1-recruiting motif) superfamily proteins are reported to be involved in microtubule assembly. However, the functions of this protein family are just beginning to be uncovered. Here, we provide metabolomic and genetic evidence that 1 of the 34 TRM members, TRM21, positively regulates the biosynthesis of flavonoids at the translational level in Arabidopsis thaliana. A loss-of-function mutation in TRM21 led to root hair growth defects and stunted plant growth, accompanied by significant alterations in secondary metabolites, particularly a marked reduction in flavonoid content. Interestingly, our study revealed that the transcription levels of genes involved in the flavonoid biosynthesis pathway remained unchanged in the trm21 mutants, but there was a significant downregulation in the translation levels of certain genes [flavanone 3-hydroxylase (F3H), dihydroflavonol-4-reductase (DFR), anthocyanidin reductase (ANR), flavanone 3’-hydroxylase (F3'H), flavonol synthase (FLS), chalcone synthase (CHS)]. Additionally, the translation levels of some genes related to root hair growth [RHO-related GTPases of plant 2 (ROP2), root hair defective 6 (RHD6), root hair defective 2 (RHD2)] were also reduced in the trm21 mutants. Taken together, these results indicate that TRM21 functions as a positive regulator of flavonoid biosynthesis at the translational level in Arabidopsis.

CtDREB52 transcription factor regulates UV-B-induced flavonoid biosynthesis by transactivating CtMYB and CtF3′H in Safflower (Carthamus tinctorius L.)

The APETALA2/ethylene-responsive element binding protein (AP2/ERF) is a highly conserved transcription factors family, involved in plant growth, development, and response to diverse stress conditions. Until recently, the AP2/ERF family has not been functionally characterized in safflower. In total, 187 AP2/ERF genes were identified from safflower genome. Phylogenetic analysis divided these CtAP2/ERFs into four distinct groups: DREB, ERFs, AP2s, and RAV genes. Furthermore, conserved protein motifs, gene structure, and cis-regulatory elements suggested important evolutionary insights into the potential role of these CtAP2/ERFs. Moreover, a comprehensive gene expression analysis conducted across various flowering stages demonstrated a consistent expression pattern of CtDREB52, which exhibited a significant correlation with alterations in the total flavonoid content. Importantly, CtDREB52 was found to be responsive to UV-B stress, and its overexpression in safflower not only promoted flavonoid accumulation but also induced an early flowering phenotype and up-regulated key genes of flavonoid pathway, while its silencing showed the opposite effect. Further, the interaction between CtDREB52 and CtDFR and CtMYB enzymes was confirmed through yeast two-hybrid and BiFC analysis. These findings provide important insights into CtDREB52-mediated regulation of flavonoid biosynthesis under UV-B stress by interacting with CtDFR and CtMYB in safflower.

Current advances of <i>Carthamus tinctorius</i> L.: a review of its application and molecular regulation of flavonoid biosynthesis

Current advances of <i>Carthamus tinctorius</i> L.: a review of its application and molecular regulation of flavonoid biosynthesis

The long noncoding RNAs lnc10 and lnc11 regulating flavonoid biosynthesis in Ginkgo biloba

Although long non-coding RNAs have been recognized to play important roles in plant, their possible functions and potential mechanism in Ginkgo biloba flavonoid biosynthesis are poorly understood. Flavonoids are important secondary metabolites and healthy components of Ginkgo biloba. They have been widely used in food, medicine, and natural health products. Most previous studies have focused on the molecular mechanisms of structural genes and transcription factors that regulate flavonoid biosynthesis. Few reports have examined the biological functions of flavonoid biosynthesis by long non-coding RNAs in G. biloba. Long noncoding RNAs associated with flavonoid biosynthesis in G. biloba have been identified through RNA sequencing, but the function of lncRNAs has not been reported. In this study, the expression levels of lnc10 and lnc11 were identified. Quantitative real-time polymerase chain reaction analysis revealed that lnc10 and lnc11 were expressed in all detected organs, and they showed significantly higher levels in immature and mature leaves than in other organs. In addition, to fully identify the function of lnc10 and lnc11 in flavonoid biosynthesis in G. biloba, lnc10 and lnc11 were cloned from G. biloba, and were transformed into Arabidopsis and overexpressed. Compared with the wild type, the flavonoid content was increased in transgenic plants. Moreover, the RNA-sequencing analysis of wild-type, lnc10-overexpression, and lnc11-overexpression plants screened out 2019 and 2552 differentially expressed genes, and the transcript levels of structural genes and transcription factors associated with flavonoid biosynthesis were higher in transgenic Arabidopsis than in the wild type, indicating that lnc10 and lnc11 activated flavonoid biosynthesis in the transgenic lines. Overall, these results suggest that lnc10 and lnc11 positively regulate flavonoid biosynthesis in G. biloba.

Transcriptomic and metabolomic analyses reveal that ABA increases the salt tolerance of rice significantly correlated with jasmonic acid biosynthesis and flavonoid biosynthesis

Abscisic acid (ABA) has been shown to mitigate the deleterious effects of abiotic stresses and to regulate plant growth and development. Salinity is one of the important abiotic stresses affecting plant cell metabolism and physiology, which causes serious damages to crops. In this study, we investigated the protective role of exogenous ABA on leaves in response to salinity stress using rice seedlings (two leaf-one heart) subjected to three treatments: ZCK (control), ZS (50 mM NaCl), and ZSA (5 mg L–1 ABA + 50 mM NaCl). We carried out transcriptomic and metabolomic analyses to identify the molecular mechanisms by which ABA protects plants against salt stress. Results showed that 1159 differentially expressed genes (DEGs) (916 up-regulated, 243 down-regulated) and 63 differentially accumulated metabolites (DAMs) (42 up-regulated, 21 down-regulated) were identified between the ZS and ZSA treatments, respectively. In addition, ABA pretreatment regulated the expression pattern of genes responsible for oxidation redox, starch and sucrose metabolism, and phenylpropanoid biosynthesis. The combined transcriptomic and metabolomic analysis revealed that 16 DEGs and 2 DAMs were involved in Flavonoid biosynthesis and 8 DEGs and 2 DAMs were involved alpha-Linolenic acid metabolism which are responsible for salinity stress tolerance through induced by exogenous ABA. Overall, ABA could enhance rice leaves growth and development mainly by regulating flavonoid biosynthesis and linoleic acid metabolism pathway.

CsMYB67 participates in the flavonoid biosynthesis of summer tea leaves.

Flavonoids are important compounds in tea leaves imparting bitter and astringent taste, which also play key roles in tea plants responding to environmental stress. Our previous study showed that the expression level of CsMYB67 was positively correlated with the accumulation of flavonoids in tea leaves as exposed to sunlight. Here, we newly reported the function of CsMYB67 in regulating flavonoid biosynthesis in tea leaves. CsMYB67 was localized in the nucleus and responded to temperature. The results of transient expression assays showed the co-transformation of CsMYB67 and CsTTG1 promoted the transcription of CsANS promoter in the tobacco system. CsTTG1 was bound to the promoter of CsANS based on the results of yeast one-hybrid (Y1H) and transient expression assays, while CsMYB67 enhanced the transcription of CsANS through protein interaction with CsTTG1 according to the results of yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC). Thus, CsMYB67-CsTTG1 module enhanced the anthocyanin biosynthesis through up-regulating the transcription of CsANS. Besides, CsMYB67 also enhanced the transcription of CsFLS and CsUFGT through forming transcription factor complexes. The function of CsMYB67 on flavonoid biosynthesis in tea leaves was validated by gene suppression assay. As CsMYB67 was suppressed, the transcriptional level of CsFLS was greatly reduced, leading to a significant increase in the contents of total catechins and total anthocyanidins. Hence, CsMYB67 plays an important role in regulating the downstream pathway of flavonoid biosynthesis in summer tea leaves.