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Dihydroquercetin (DHQ), an extremely low content compound (less than 3%) in plants, is an important component of dietary supplements and used as functional food for its antioxidant activity. Moreover, as downstream metabolites of DHQ, an extremely high content of dihydromyricetin (DHM) is up to 38.5% in Ampelopsis grossedentata. However, the mechanisms involved in the biosynthesis and regulation from DHQ to DHM in A. grossedentata remain unclear. In this study, a comparative transcriptome analysis of A. grossedentata containing extreme amounts of DHM was performed on the Illumina HiSeq 2000 sequencing platform. A total of 167,415,597 high-quality clean reads were obtained and assembled into 100,584 unigenes having an N50 value of 1489. Among these contigs, 57,016 (56.68%) were successfully annotated in seven public protein databases. From the differentially expressed gene (DEG) analysis, 926 DEGs were identified between the B group (low DHM: 210.31 mg/g) and D group (high DHM: 359.12 mg/g) libraries, including 446 up-regulated genes and 480 down-regulated genes (B vs. D). Flavonoids (DHQ, DHM)-related DEGs of ten structural enzyme genes, three myeloblastosis transcription factors (MYB TFs), one basic helix–loop–helix (bHLH) TF, and one WD40 domain-containing protein were obtained. The enzyme genes comprised three PALs , two CLs , two CHSs , one F3’H , one F3’5’H (directly converts DHQ to DHM), and one ANS . The expression profiles of randomly selected genes were consistent with the RNA-seq results. Our findings thus provide comprehensive gene expression resources for revealing the molecular mechanism from DHQ to DHM in A. grossedentata . Importantly, this work will spur further genetic studies about A. grossedentata and may eventually lead to genetic improvements of the DHQ content in this plant.

The authors wish to thank the Spanish Ministry of Economy and Competitiveness (MINECO, for financial support via Grant AGL2010-20622), and also to the Government of the Principality of Asturias (program PCTI for a Technology Transfer Grant).

Cytochrome P450 monooxygenases (P450) in the honey bee, Apis mellifera, detoxify phytochemicals in honey and pollen. The flavonol quercetin is found ubiquitously and abundantly in pollen and frequently at lower concentrations in honey. Worker jelly consumed during the first 3 d of larval development typically contains flavonols at very low levels, however. RNA-Seq analysis of gene expression in neonates reared for three days on diets with and without quercetin revealed that, in addition to up-regulating multiple detoxifying P450 genes, quercetin is a negative transcriptional regulator of mitochondrion-related nuclear genes and genes encoding subunits of complexes I, III, IV, and V in the oxidative phosphorylation pathway. Thus, a consequence of inefficient metabolism of this phytochemical may be compromised energy production. Several P450s metabolize quercetin in adult workers. Docking in silico of 121 pesticide contaminants of American hives into the active pocket of CYP9Q1, a broadly substrate-specific P450 with high quercetin-metabolizing activity, identified six triazole fungicides, all fungal P450 inhibitors, that dock in the catalytic site. In adults fed combinations of quercetin and the triazole myclobutanil, the expression of five of six mitochondrion-related nuclear genes was down-regulated. Midgut metabolism assays verified that adult bees consuming quercetin with myclobutanil metabolized less quercetin and produced less thoracic ATP, the energy source for flight muscles. Although fungicides lack acute toxicity, they may influence bee health by interfering with quercetin detoxification, thereby compromising mitochondrial regeneration and ATP production. Thus, agricultural use of triazole fungicides may put bees at risk of being unable to extract sufficient energy from their natural food.

Background Yeast peroxisomes have been engineered as ideal synthetic compartments to enhance the heterologous biosynthesis of natural products, particularly terpenoids and fatty acid derivatives. This advantage is primarily attributed to the rich acetyl-CoA pool generated from the spatially specific fatty acid β -oxidation within peroxisomes. However, their potential for flavonoid biosynthesis has been largely underexplored, primarily due to limited knowledge regarding precursor transport, cofactor availability, and the redox environment in peroxisomes. Results In this study, we successfully compartmentalized the biosynthesis of taxifolin, a dihydroflavonol, in Saccharomyces cerevisiae peroxisomes. The result indicated that flavonoid biosynthesis in peroxisome offers a more efficient approach compared to its synthesis in the cytosol. This study managed to expand the application scope of peroxisome compartmentalization to flavonoid biosynthesis. By reinforcing the rate-limiting steps, optimizing cofactor supply and activation of fatty acids, we accomplished the de novo synthesis of taxifolin in peroxisomes for the first time, attaining a titer of 120.3 ± 2.4 mg/L in shake-flask fermentation using a minimal medium. Conclusion These findings highlight the feasibility of peroxisomal compartmentalization for flavonoid biosynthesis, providing new insights and a framework for the biosynthesis of other high-value flavonoids using yeast peroxisomes.

Despite controlling a diverse array of regulatory processes in plants, UV-B wavelengths (280–315 nm) are attenuated by common greenhouse materials such as glass and polycarbonate and are therefore depleted in many commercial growing environments. In this study, we analysed the architecture, pigment accumulation and antioxidant capacity of coriander ( Coriandrum sativum , also known as cilantro) plants grown with and without supplementary UV-B (1.5 µmol m −2 s −1 ). We demonstrate that UV-B limits stem elongation responses to neighbour proximity perception (shade avoidance), promoting a more compact plant architecture. In addition, UV-B increased leaf quercetin content and total antioxidant capacity. Arabidopsis thaliana mutants deficient in flavonoid biosynthesis were not impaired in shade avoidance inhibition, suggesting that UV-B-induced flavonoid synthesis is not a component of this response. Our results indicate that UV-B supplementation may provide a method to manipulate the architecture, flavour and nutritional content of potted herbs whilst reducing the deleterious impacts of dense planting on product quality.

An investigation was conducted through transcriptome sequencing in various tissues at different stages to explore the quercetin biosynthesis pathway in Euphorbia maculata . A total of 83,028 unigenes was assembled utilizing Trinity software, with an N50 length of 1721 bp and a mean length of 1004 bp. Among these unigenes, 51,822 were annotated in six public databases. The transcriptome analysis revealed 45,727 CDS sequences and 56 TF families. Candidate genes involved in quercetin biosynthesis were also revealed, including phenylalanine ammonia-lyase (17 unigenes), cinnamate 4-hydroxylase (3 unigenes), 4-coumarate-CoA ligase (16 unigenes), chalcone synthase (5 unigenes), chalcone isomerase (4 unigenes), flavanone 3-hydroxylase (1 unigene), flavonoid 3′-hydroxylase (4 unigenes), and flavonol synthase (9 unigenes). Additionally, 42 key differentially expressed genes (DEGs) related to quercetin biosynthesis were identified in the same tissues at different stages, with 35 DEGs exhibiting down-regulated expression and 7 DEGs displaying up-regulated expression. These findings not only enhance the genetic knowledge of E. maculata , but also establish a basis for further investigating the mechanism of quercetin biosynthesis, and improving the quality of E. maculata .

Flavonoids have gained much attention for their proposed positive effects for human health. Glycosylation is a significant method for the structural modification of various flavanols, resulting in glycosides with increased solubility, stability, and bioavailability compared with the corresponding aglycone. Natural product glycosylation by using enzymes has emerged as a topic of interest as it offers a sustainable and economical alternative source so as to address supply scalability limitations associated with plant-based production. Quercetin-3,4′-O-diglucoside, as one of the major but trace bioactive flavonoids in onion (Allium cepa), is superior or at least equal to quercetin aglycone in its bioavailability. In the present study, the onion-derived enzyme, UGT73G1, coupled with sucrose synthase, StSUS1, from Solanum tuberosum formed a circulatory system to produce quercetin-3,4′-O-diglucoside from quercetin, which preferred sucrose as a sugar donor and quercetin as a sugar acceptor. The optimal conditions were determined in order to increase the production of quercetin-3,4′-O-diglucoside. The maximum concentration of quercetin-3,4′-O-diglucoside achieved in a 10-mL reaction was 427.11 mg/L, from the conversion of 1 g/L of quercetin for 16 h at 40 °C and pH 7.2.

A small Chilean variety of pears growing in the town of Toconao, an oasis located at the northeastern edge of the Salar de Atacama, northern Chile, was studied by means of modern PDA and high resolution mass spectral data (UHPLC-PDA-HESI-orbitrap-MS/MS). In addition, the antioxidant features of the fruits were compared with the varieties Packhman’s Triumph and Abate Fetel and correlated with the presence of phenolic compounds. The non-pigmented phenolics were fingerprinted and related to the antioxidant capacities measured by the bleaching of the DPPH radical, the ferric reducing antioxidant power (FRAP), the superoxide anion scavenging activity assay (SA), and total content of phenolics and flavonoids measured by spectroscopic methods. The machine allowed a fast separation of 15 min employing a flow rate of 1 mL per minute and could accurately identify 25 compounds, including several isorhamnetin derivatives and phenolic acids, present in the peel and pulps of this Chilean variety for the first time. The compounds were monitored using a wavelength range of 210–800 nm. The native small Chilean pear showed the highest antioxidant activity measured as the bleaching of the DPPH radical, the ferric reducing antioxidant power and superoxide anion scavenging activity (8.61 ± 0.65 μg/mL, 712.63 ± 12.12 micromols trolox equivalents (μmol/TE)/100 g FW, and 82.89% ± 2.52% at 100 μg/mL, respectively).

Taxifolin, also known as dihydroquercetin (DHQ), is a flavonoid recognized for its potent antioxidant properties and a wide range of biological activities, including anti-tumor, antiviral, and immunomodulatory effects. Conventional extraction and chemical synthesis methods for taxifolin are often limited by low yields and associated environmental concerns. In this study, we investigated the heterologous biosynthesis of taxifolin in Yarrowia lipolytica through a combination of metabolic engineering and genome-scale metabolic modeling (GSM), complemented by flux balance analysis (FBA). We engineered Yarrowia lipolytica by introducing key biosynthetic genes and successfully synthesized taxifolin using naringenin (NAR) as a substrate, chosen for its low cost. Fermentation experiments demonstrated an optimal taxifolin yield of 10% at a substrate concentration of 200 mg/L naringenin, with a maximum yield of 26.4 mg/L taxifolin at 1 g/L naringenin. To further enhance production, we applied a marker-free Cre-loxP-based gene integration method, allowing stable genomic integration of key genes, which increased taxifolin yield to 34.9 mg/L at 1 g/L naringenin. Additionally, intermediate metabolites eriodictyol (ERI) and dihydrokaempferol (DHK) accumulated to concentrations of 89.2 mg/L and 21.7 mg/L, respectively. Furthermore, we integrated metabolic data into a GSM and applied FBA to optimize the taxifolin biosynthetic pathway. Through Pareto frontier analysis, sensitivity analysis, flux variability analysis, and single gene deletion simulations, we identified key genetic modifications that significantly enhanced taxifolin yield. Overexpression of GND1 and IDP2 increased yields by 94% and 155%, respectively, while knockout of LIP2 led to a 46% increase. Using tri-baffled shake flasks to improve oxygen supply resulted in a 120% yield increase, whereas YPG medium decreased yield by 59%, validating our model’s accuracy. To ensure stable and efficient gene expression, we integrated multi-copy constructs into the ribosomal DNA (rDNA) locus of Yarrowia lipolytica , doubling taxifolin production. These results demonstrate the effectiveness of GSM and FBA in addressing bottlenecks in microbial taxifolin biosynthesis and provide a basis for future optimization and large-scale production.

Quercetin, a flavonol aglycone, is one of the most abundant flavonoids with high medicinal value. The bioavailability and pharmacokinetic properties of quercetin are influenced by the type of sugars attached to the molecule. To efficiently diversify the therapeutic uses of quercetin, Escherichia coli was harnessed as a production factory by the installation of various plant and bacterial UDP-xylose sugar biosynthetic genes. The genes encoding for the UDP-xylose pathway enzymes phosphoglucomutase ( nfa44530 ), glucose-1-phosphate uridylyltransferase ( galU ), UDP-glucose dehydrogenase ( calS8 ), and UDP-glucuronic acid decarboxylase ( calS9 ) were overexpressed in E. coli BL21 (DE3) along with a glycosyltransferase ( arGt-3 ) from Arabidopsis thaliana . Furthermore, E. coli BL21(DE3)/∆ pgi , E. coli BL21(DE3)/∆ zwf , E. coli BL21(DE3)/∆ pgi ∆ zwf , and E. coli BL21(DE3)/∆ pgi ∆ zwf ∆ ushA mutants carrying the aforementioned UDP-xylose sugar biosynthetic genes and glycosyltransferase and the galU -integrated E. coli BL21(DE3)/∆ pgi host harboring only calS8 , calS9 , and arGt-3 were constructed to enhance whole-cell bioconversion of exogeneously supplied quercetin into 3- O -xylosyl quercetin. Here, we report the highest production of 3- O -xylosyl quercetin with E. coli BL21 (DE3)/∆ pgi ∆ zwf ∆ ushA carrying UDP-xylose sugar biosynthetic genes and glycosyltransferase. The maximum concentration of 3- O -xylosyl quercetin achieved was 23.78 mg/L (54.75 μM), representing 54.75 % bioconversion, which was an ~4.8-fold higher bioconversion than that shown by E. coli BL21 (DE3) with the same set of genes when the reaction was carried out in 5-mL culture tubes with 100 μM quercetin under optimized conditions. Bioconversion was further improved by 98 % when the reaction was scaled up in a 3-L fermentor at 36 h.