Mechanism Of Flavonoid Biosynthesis Research Articles

Identification of One O-Methyltransferase Gene Involved in Methylated Flavonoid Biosynthesis Related to the UV-B Irradiation Response in Euphorbia lathyris.

Flavonoids are ubiquitous polyphenolic compounds that play a vital role in plants' defense response and medicinal efficacy. UV-B radiation is a vital environmental regulator governing flavonoid biosynthesis in plants. Many plants rapidly biosynthesize flavonoids as a response to UV-B stress conditions. Here, we investigated the effects of flavonoid biosynthesis via UV-B irradiation in Euphorbia lathyris. We found that exposure of the E. lathyris callus to UV-B radiation sharply increased the level of one O-methyltransferase (ElOMT1) transcript and led to the biosynthesis of several methylated flavonoids. The methyltransferase ElOMT1 was expressed heterologously in E. coli, and we tested the catalytic activity of recombinant ElOMT1 with possible substrates, including caffeic acid, baicalin, and luteolin, in vitro. ElOMT1 could efficiently methylate when the hydroxyl groups were contained in the core nucleus of the flavonoid. This molecular characterization identifies a methyltransferase responsible for the chemical modification of the core flavonoid structure through methylation and helps reveal the mechanism of methylated flavonoid biosynthesis in Euphorbiaceae. This study identifies the O-methyltransferase that responds to UV-B irradiation and helps shed light on the mechanism of flavonoid biosynthesis in Euphorbia lathyris.

Combined Transcriptomic and Metabolomic Analysis Reveals the Mechanism of Flavonoid Biosynthesis in Handroanthus chrysanthus (Jacq.) S.O.Grose

Handroanthus and Tabebuia are known for their ornamental and medicinal value, which are attributed to metabolites. However, the mechanisms underlying the synthesis of these metabolites are poorly understood. In this study, the expression levels of secondary metabolites and the mechanism of flavonoid biosynthesis in the bark and leaves of Handroanthus chrysantha (Jaq.) were examined using transcriptomic and metabolomic techniques. Metabolic analysis identified several differentially accumulated metabolites (DAMs), most of which were flavonoids, isoprenoids, and sterols. Additionally, 30 flavonoids were identified in the bark and leaves of H. chrysantha. Transcriptomic analysis identified 69 genes involved in flavonoid biosynthesis, among which 49 were significantly different between the bark and leaves. qRT-PCR analysis of eight genes involved in flavonoid biosynthesis showed that the expression patterns of the genes were consistent with the transcriptome sequencing data. Integrative transcriptomic and metabolomic analysis showed that 20 differentially expressed genes (DEGs) associated with flavonoid biosynthesis were strongly correlated with seven DAMs, confirming the involvement of the DEGs in flavonoid biosynthesis. These findings considerably contribute to the understanding of the biosynthesis of secondary metabolites in H. chrysantha and serve as a reference for further pharmacological studies.

Metabolome and transcriptome profiling reveal regulatory network and mechanism of flavonoid biosynthesis during color formation of Dioscorea cirrhosa L.

Dioscorea cirrhosa is a plant that is used as a dye as well as in medicine. Many metabolites with pharmacological activity exist in the tubers of D. cirrhosa. However, little is known about the mechanism regulating biosynthesis in these metabolites. In this study, transcriptome and metabolome profiling were performed in four color tubers. A total of 531 metabolites, including 62 flavonoids, were identified. Epicatechin and proanthocyanin B2 were the key metabolites that exhibited high content levels in the four tubers. These metabolites were divided into nine classes with distinct change patterns. A total of 22,865 differentially expressed genes (DEGs) were identified by transcriptome analysis. Among these DEGs, we identified 67 candidate genes related to the flavonoid biosynthesis pathway and three genes that played pivotal roles in proanthocyanin (PA) synthesis. A weighted gene co-expression network analysis (WGCNA) revealed that the two modules, “MEblue” and “MEblack,” were two key gene sets strongly associated with phenylpropanoid and flavonoid biosynthesis. We also found that the plant hormone signal transduction biological process exhibited activity in the late stage of tuber color formation. Additionally, we identified 37 hub transcript factors related to flavonoid biosynthesis, of which 24 were found to be highly associated with flavonoid pathway genes. In addition to the MYB-bHLH-WD40 (MBW) genes, we found that the plant hormone gene families exhibited high expression levels. This study provides a reference for understanding the synthesis of D. cirrhosa tuber metabolites at the molecular level and provides a foundation for the further development of D. cirrhosa related plant pigments as well as its further use in the pharmaceutical industry.

Integrated Analysis of Metabolome and Transcriptome Data for Uncovering Flavonoid Components of Zanthoxylum bungeanum Maxim. Leaves Under Drought Stress.

Zanthoxylum bungeanum Maxim. leaves (ZBLs) are rich in flavonoids and have become popular in nutrition, foods and medicine. However, the flavonoid components in ZBLs and the mechanism of flavonoid biosynthesis under drought stress have received little attention. Here, we performed an integrative analysis of the metabolome and transcriptome of ZBLs from HJ (Z. bungeanum cv. “Hanjiao”) and FJ (Z. bungeanum cv. “Fengjiao”) at four drought stages. A total of 231 individual flavonoids divided into nine classes were identified and flavones and flavonols were considered the most abundant flavonoid components in ZBLs. The total flavonoid content of ZBLs was higher in FJ; it increased in FJ under drought stress but decreased in HJ. Nine-quadrant analysis identified five and eight differentially abundant flavonoids in FJ and HJ leaves, respectively, under drought stress. Weighted gene correlation network analysis (WGCNA) identified nine structural genes and eight transcription factor genes involved in the regulation of flavonoid biosynthesis. Moreover, qRT-PCR results verified the accuracy of the transcriptome data and the reliability of the candidate genes. Taken together, our results reveal the flavonoid components of ZBLs and document changes in flavonoid metabolism under drought stress, providing valuable information for nutrition value and food utilization of ZBLs.

Integrative Analysis of the Metabolome and Transcriptome Provides Novel Insights into the Mechanisms of Flavonoid Biosynthesis in Camellia Lanceoleosa

Integrative Analysis of the Metabolome and Transcriptome Provides Novel Insights into the Mechanisms of Flavonoid Biosynthesis in Camellia Lanceoleosa

Integrated metabolome and transcriptome revealed the flavonoid biosynthetic pathway in developing Vernonia amygdalina leaves.

BackgroundVernonia amygdalina as a tropical horticultural crop has been widely used for medicinal herb, feed, and vegetable. Recently, increasing studies revealed that this species possesses multiple pharmacological properties. Notably, V. amygdalina leaves possess an abundance of flavonoids, but the specific profiles of flavonoids and the mechanisms of fl avonoid bi osynthesis in developing leaves are largely unknown.MethodsThe total flavonoids of V. amygdalina leaves were detected using ultraviolet spectrophotometer. The temporal flavonoid profiles of V. amygdalina leaves were analyzed by LC-MS. The transcriptome analysis of V. amygdalina leaves was performed by Illumina sequencing. Functional annotation and differential expression analysis of V. amygdalina genes were performed by Blast2GO v2.3.5 and RSEM v1.2.31, respectively. qRT-PCR analysis was used to verify the gene expressions in developing V. amygdalina leaves.ResultsBy LC-MS analysis, three substrates (p-coumaric acid, trans-cinnamic acid, and phenylalanine) for flavonoid biosynthesis were identified in V. amygdalina leaves. Additionally, 42 flavonoids were identified from V. amygdalina leaves, including six dihydroflavones, 14 flavones, eight isoflavones, nine flavonols, two xanthones, one chalcone, one cyanidin, and one dihydroflavonol. Glycosylation and methylation were common at the hydroxy group of C3, C7, and C4’ positions. Moreover, dynamic patterns of different flavonoids showed diversity. By Illumina sequencing, the obtained over 200 million valid reads were assembled into 60,422 genes. Blast analysis indicated that 31,872 genes were annotated at least in one of public databases. Greatly increasing molecular resources makes up for the lack of gene information in V. amygdalina. By digital expression profiling and qRT-PCR, we specifically characterized some key enzymes, such as Va-PAL1, Va-PAL4, Va-C4H1, Va-4CL3, Va-ACC1, Va-CHS1, Va-CHI, Va-FNSII, and Va-IFS3, involved in flavonoid biosynthesis. Importantly, integrated metabolome and transcriptome data of V. amygdalina leaves, we systematically constructed a flavonoid biosynthetic pathway with regards to material supplying, flavonoid scaffold biosynthesis, and flavonoid modifications. Our findings contribute significantly to understand the underlying mechanisms of flavonoid biosynthesis in V. amygdalina leaves, and also provide valuable information for potential metabolic engineering.

CsMYB60 directly and indirectly activates structural genes to promote the biosynthesis of flavonols and proanthocyanidins in cucumber

Flavonols and proanthocyanidins (PAs) are the main pigments in the black spines of cucumber (Cucumis sativus) fruit, and CsMYB60 is a key regulator of the biosynthesis of flavonols and PAs. However, in cucumber, the tissue distribution pattern of flavonols and PAs and the mechanism of their biosynthesis regulated by CsMYB60 remain unclear. In this study, we clarified the tissue-specific distribution of flavonoids and the unique transcriptional regulation of flavonoid biosynthesis in cucumber. CsMYB60 activated CsFLS and CsLAR by binding to their promoters and directly or indirectly promoted the expression of CsbHLH42, CsMYC1, CsWD40, and CsTATA-box binding protein, resulting in the formation of complexes of these four proteins to increase the expression of Cs4CL and interact with CsTATA-box binding protein to regulate the expression of CsCHS, thereby regulating the biosynthesis of flavonols and PAs in cucumber. Our data provide new insights into the molecular mechanism of flavonoid biosynthesis, which will facilitate molecular breeding to improve fruit quality in cucumber.

Accumulation of flavonoids and related gene expressions in different organs of Astragalus membranaceus Bge.

Astragalus membranaceus is one of the important medicinal plant in China and Korea. It is used to increase metabolism and digestion, enhance the immune system, and promote the healing of wounds and injuries. In the present study, we used quantitative real-time PCR to investigate the expression of genes related to the biosynthesis of flavonoids, in addition to high-performance liquid chromatography to assess calycosin and calycosin-7-O-β-D-glucoside accumulation, in the different plant organs of A. membranaceus. The transcript levels of all genes (AmPAL, AmC4H, Am4CL, AmCHS, AmCHR, AmCHI, AmIFS, AmI3'H, and AmUCGT) involved in calycosin and calycosin-7-O-β-D-glucoside biosynthesis were the highest in the flower. Calycosin content was ordered as follows: leaf (145.56 μg/g dry weight [DW]) > stem (18.3 μg/g DW) > root (1.64 μg/g DW) > flower (0.09 μg/g DW), whereas calycosin-7-O-β-D-glucoside content was ordered as follows: root (4.88 μg/g DW) > stem (3.86 μg/g DW) > leaf (2.0 μg/g DW) > flower (not detected). All genes exhibited the highest transcription levels in the flower, whereas calycosin and its glycoside content were the highest in the leaf and root, respectively. Our results indicate that the enhancement of calycosin-7-O-β-D-glucoside in the roots may originate from high calycosin accumulation in the stem and leaf. Thus, the mechanisms regulating calycosin and calycosin-7-O-β-D-glucoside content differ in the different organs of A. membranaceus. The results are expected to provide baseline information from which the mechanism of flavonoid biosynthesis in the different organs of A. membranaceus may be elucidated.