Identification of Specific Glycosyltransferases Involved in Flavonol Glucoside Biosynthesis in Ginseng Using Integrative Metabolite Profiles, DIA Proteomics, and Phylogenetic Analysis

Four novel Cit7GlcTs functional in flavonoid 7-O-glucoside biosynthesis are vital to flavonoid biosynthesis shunting in citrus

Citrus fruits have abundant flavonoid glycosides (FGs), an important class of natural functional and flavor components. However, there have been few reports about the modification of UDP-glycosyltransferases (UGTs) on flavonoids in citrus. Notably, in flavonoid biosynthesis, 7-O-glucosylation is the initial and essential step of glycosylation prior to the synthesis of flavanone disaccharides, the most abundant and iconic FGs in citrus fruits. Here, based on the accumulation of FGs observed at the very early fruit development stage of two pummelo varieties, we screened six novel flavonoid 7-O-glucosyltransferase genes (7GlcTs) via transcriptomic analysis and then characterized them in vitro. The results revealed that four Cg7GlcTs possess wide catalytic activities towards various flavonoid substrates, with CgUGT89AK1 exhibiting the highest catalytic efficiency. Transient overexpression of CgUGT90A31 and CgUGT89AK1 led to increases in FG synthesis in pummelo leaves. Interestingly, these two genes had conserved sequences and consistent functions across different germplasms. Moreover, CitUGT89AK1 was found to play a role in the response of citrus to Huanglongbing infection by promoting FG production. The findings improve our understanding of flavonoid 7-O-glucosylation by identifying the key genes, and may help improve the benefits of flavonoid biosynthesis for plants and humans in the future.

Integrated Full-Length Transcriptomics and Metabolomics Reveal Glycosyltransferase Involved in the Biosynthesis of Flavonol Glycosides in Laportea bulbifera

Many species of the Urticaceae family are important cultivated fiber plants that are known for their economic and industrial values. However, their secondary metabolite profiles and associated biosynthetic mechanisms have not been well-studied. Using Laportea bulbifera as a model, we conducted widely targeted metabolomics, which revealed 523 secondary metabolites, including a unique accumulation of flavonol glycosides in bulblet. Through full-length transcriptomic and RNA-seq analyses, the related genes in the flavonoid biosynthesis pathway were identified. Finally, weighted gene correlation network analysis and functional characterization revealed four LbUGTs, including LbUGT78AE1, LbUGT72CT1, LbUGT71BX1, and LbUGT71BX2, can catalyze the glycosylation of flavonol aglycones (kaempferol, myricetin, gossypetin, and quercetagetin) using UDP-Gal and UDP-Glu as the sugar donors. LbUGT78AE1 and LbUGT72CT1 showed substrate promiscuity, whereas LbUGT71BX1 and LbUGT71BX2 exhibited different substrate and sugar donor selectivity. These results provide a genetic resource for studying Laportea in the Urticaceae family, as well as key enzymes responsible for the metabolism of valuable flavonoid glycosides.

Development and comparison of parallel reaction monitoring and data-independent acquisition methods for quantitative analysis of hydrophilic compounds in white tea

In the present work, parallel reaction monitoring (PRM) and data-independent acquisition (DIA) methods were developed for the accurate quantitation of amino acids, alkaloids nucleosides and nucleotides in tea. The quality peaks were significantly enhanced by optimizing the LC elution procedure, HCD voltage, MS resolution, and scanning event. Both methods were validated with good liner linearity (0.004-200 μg/mL), LODs (0.001-0.309 μg/mL for PRM and 0.001-0.564 μg/mL for DIA). Applied to white tea sample, the contents of these hydrophilic compounds were range from 34,655.39 to 70,586.14 mg/kg, and caffeine (32,529.02 mg/kg) and theanine (5483.46 mg/kg) were determined as the most abundant ones. Based on the quantitation data set, the white tea samples from Puer, Lincang and Xishuangbanna were clearly discriminated using multivariate data analysis. The results of the present works show that PRM and DIA have great potential in quantitative analysis of multiple hydrophilic compounds in food samples.

Multi-omics reveal key enzymes involved in the formation of phenylpropanoid glucosides in Artemisia annua

Although mainly known for producing artemisinin, Artemisia annua is enriched in phenylpropanoid glucosides (PGs) with significant bioactivities. However, the biosynthesis of A. annua PGs is insufficiently investigated. Different A. annua ecotypes from distinct growing environments accumulate varying amounts of metabolites, including artemisinin and PGs such as scopolin. UDP-glucose:phenylpropanoid glucosyltransferases (UGTs) transfers glucose from UDP-glucose in PG biosynthesis. Here, we found that the low-artemisinin ecotype GS produces a higher amount of scopolin, compared to the high-artemisinin ecotype HN. By combining transcriptome and proteome analyses, we selected 28 candidate AaUGTs from 177 annotated AaUGTs. Using AlphaFold structural prediction and molecular docking, we determined the binding affinities of 16 AaUGTs. Seven of the AaUGTs enzymatically glycosylated phenylpropanoids. AaUGT25 converted scopoletin to scopolin and esculetin to esculin. The lack of accumulation of esculin in the leaf and the high catalytic efficiency of AaUGT25 on esculetin suggest that esculetin is methylated to scopoletin, the precursor of scopolin. We also discovered that AaOMT1, a previously uncharacterized O-methyltransferase, converts esculetin to scopoletin, suggesting an alternative route for producing scopoletin, which contributes to the high-level accumulation of scopolin in A. annua leaves. AaUGT1 and AaUGT25 responded to induction of stress-related phytohormones, implying the involvement of PGs in stress responses.

Jinfeng pills ameliorate premature ovarian insufficiency induced by cyclophosphamide in rats and correlate to modulating IL-17A/IL-6 axis and MEK/ERK signals

ETHNOPHARMACOLOGICAL RELEVANCE

Jinfeng Pill (JFP) is a classical Chinese medicine formula and composed of 9 herbs, including Epimedium brevicornu Maxim (Yinyanghuo), Cervus elaphus Linnaeus (Lurong), Panax ginseng C.A.Mey. (Renshen), Equus asinus (EJiao), Ligustrum lucidum W.T.Aiton (Nvzhenzi), Reynoutria multiflora (Thunb.) Moldenke (Heshouwu), Curculigo orchioides Gaertn (Xianmao), Neolitsea cassia (L.) Kosterm. (Rougui) and Leonurus japonicus Houtt. (Yimucao). The formula is clinically used to regulate menstrual cycle and alleviate polycystic ovarian syndrome due to its capabilities of ovulation induction. It is therefore presumed that JFP could be used for the therapy of premature ovarian insufficiency (POI) but the assumed efficacy has not been fully substantiated in experiment.

AIM OF STUDY

To evaluate the effectiveness of JFP on cyclophosphamide (CTX)-induced POI and preliminarily explore its potential mechanisms of action.

MATERIAL AND METHODS

An experimental rat model of POI was established by using CTX induction to assess the efficacy of JFP. The potential targets of action for JFP alleviating POI were predicted by the combination of network pharmacology and transcriptomics and finally validating by RT-qPCR and Western blot.

RESULTS

JFP alleviated the damages of ovarian tissue induced by CTX in the rat model of POI via significantly decreasing serum levels of FSH and LH and the ratio of FSH/LH and increasing the levels of E2 and AMH, accompanied with promoting ovarian folliculogenesis and follicle maturity and reversing the depletion of follicle pool. With the analysis of network pharmacology, pathways in cancer, proteoglycans in cancer, PI3K-AKT, TNF and FoxO signaling pathways were predicted to be influenced by JFP. The results of RNA-seq further revealed that IL-17 signaling pathway was the most important pathway regulated by both CTX and JFP, following by transcriptional misregulation in cancer and proteoglycans in cancer. Combining the two analytical methods, JFP likely targeted genes associated with immune regulation, including COX-2, HSP90AA1, FOS, MMP3 and MAPK11 and pathways, including IL-17,Th17 cell differentiation and TNF signaling pathway. Finally, JFP was validated to regulate the mRNA expression of FOS, FOSB, FOSL1, MMP3, MMP13 and COX-2 and decrease the release of IL-17A and the protein expression of IL-6 and suppress the phosphorylation of MEK1/2 and ERK1/2 in CTX induced POI rats.

CONCLUSION

Jinfeng Pill is effective to ameliorate the symptoms of POI induced by CTX in the model of rats and its action is likely associated with suppressing IL-17A/IL-6 axis and the activity of MEK1/2-ERK1/2 signaling.

Structural, in vitro digestion, and fermentation characteristics of lotus leaf flavonoids

Bioaccessibility and bioactivity of flavonoids in lotus leaves are related to their characteristics in gastrointestinal digestion and colonic fermentation. The aim of this study is to investigate the stability of lotus leaf flavonoids (LLF) in simulated gastrointestinal digestion, and its modulation on gut microbiota in vitro fermentation. Results showed that LLF mainly consisted of quercetin-3-O-galactoside, quercetin-3-O-glucuronide, quercetin-3-O-glucoside, and kaempferol-3-O-glucoside. These flavonoids kept stability with only a small fraction degraded in simulated gastric and intestinal fluids. In vitro fermentation, LLF stimulated the growth of Actinobacteria and Firmicutes, inhibited the growth of Proteobacteria, and induced the production of fermentation gases and short-chain fatty acids. Interestingly, supplementation of soluble starch significantly improved the utilization of LLF by the intestinal flora. These results revealed that LLF shaped a unique biological web with Lactobacillus and Bifidobacterium spp. as the core of the biological network, which would be more beneficial to gut health.

Unraveling multifunction of low-temperature Daqu in simultaneous saccharification and fermentation of Chinese light aroma type liquor

Chinese liquor is produced by a representative simultaneous saccharification and fermentation process. Daqu, as a starter of Chinese liquor fermentation, affects both saccharification and fermentation. However, it is still unclear how Daqu contributed to the simultaneous saccharification and fermentation process. Here, using Chinese light aroma type liquor as a case, we identified low-temperature Daqu-originated enzymes and microorganisms that contributed to the simultaneous saccharification and fermentation using metaproteomic analysis combined with amplicon sequencing analysis. α-Amylase and glucoamylase accounted for 95 % of total saccharifying enzymes and were identified as key saccharifying enzymes. Lichtheimia was the key producer of these two enzymes (> 90 %) in low-temperature Daqu. Daqu contributed 90 % α-amylase and 99 % glucoamylase to the initial liquor fermentation. These two enzymes decreased by 35 % and 49 % until day 15 in liquor fermentation. In addition, Daqu contributed key microbial genera (91 % Saccharomyces, 6.5 % Companilactobacillus) and key enzymes (37 % alcohol dehydrogenase, 40 % lactic acid dehydrogenase, 56 % aldehyde dehydrogenase) related with formations of ethanol, lactic acid and flavour compounds to the initial liquor fermentation. The average relative abundances of these fermentation-related key microorganisms and enzymes increased by 2.78 times and 1.29 times till day 15 in liquor fermentation, respectively. It indicated that Daqu provided saccharifying enzymes for starch hydrolysis, and provided both enzymes and microorganisms associated with formations of ethanol, lactic acid and flavour compounds for liquor fermentation. This work illustrated the multifunction of low-temperature Daqu in the simultaneous saccharification and fermentation of Chinese light aroma type liquor. It would facilitate improving liquor fermentation by producing high-quality Daqu.

Integrated Transcriptomic and Metabolomic Analyses Reveal the Molecular and Metabolic Basis of Flavonoids in Areca catechu L

Areca catechu L., of the Arecaceae family, is widely distributed in tropical Asia. In A. catechu, the extracts and compounds, including flavonoids, have various pharmacological activities. Although there are many studies of flavonoids, the molecular mechanism of their biosynthesis and regulation remains unclear in A. catechu. In this study, 331 metabolites were identified from the root, stem, and leaf of A. catechu using untargeted metabolomics, including 107 flavonoids, 71 lipids, 44 amino acids and derivatives, and 33 alkaloids. The transcriptome analysis identified 6119 differentially expressed genes, and some were enriched in the flavonoid pathway. To analyze the biosynthetic mechanism of the metabolic differences in A. catechu tissues, 36 genes were identified through combined transcriptomic and metabolomic analysis, in which glycosyltransferase genes Acat_15g017010 and Acat_16g013670 were annotated as being involved in the glycosylation of kaempferol and chrysin by their expression and in vitro activities. Flavonoid biosynthesis could be regulated by the transcription factors, AcMYB5 and AcMYB194. This study laid a foundation for further research on the flavonoid biosynthetic pathway of A. catechu.

Exogenously applied melatonin alleviates the damage in cucumber plants caused by Aphis goosypii through altering the insect behavior and inducing host plant resistance

BACKGROUND

Aphis gossypii Glover is the main pest found in most cucumber-producing areas. Melatonin (MT) has been widely studied in protecting plants from environmental stresses and pathogens. However, little knowledge is available on the impact of MT on insect resistance.

RESULTS

The fecundity of aphids on MT-treated cucumber leaves was inhibited. Interestingly, MT-treated plants were more attractive to aphids, which would prevent the large-scale transmission of viruses caused by the random movement of aphids. Meanwhile, MT caused varying degrees of change in enzyme activities related to methylesterified HG degradation, antioxidants, defense systems and membrane lipid peroxidation. Furthermore, transcriptomic analysis showed that MT induced 2360 differentially expressed genes (DEGs) compared with the control before aphid infection. These DEGs mainly were enriched in hormone signal transduction, MAPK signaling pathway, and plant-pathogen interaction, revealing that MT can help plants acquire inducible resistance and enhance plant immunity. Subsequently, 2397 DEGs were identified after aphid infection. Further analysis showed that MT-treated plants possessed stronger JA signal, reactive oxygen species stability, and the ability of flavonoid synthesis under aphid infection, while mediating plant growth and sucrose metabolism.

CONCLUSION

In summary, MT as an environmentally friendly substance mitigated aphid damage to cucumbers by affecting the aphids themselves and enhancing plant resistance. This will facilitate exploring sustainable MT-based strategies for cucumber aphid control. © 2022 Society of Chemical Industry.

Integrated multi-omics analysis and microbial recombinant protein system reveal hydroxylation and glycosylation involving nevadensin biosynthesis in Lysionotus pauciflorus

Background

Karst-adapted plant, Lysionotus pauciflours accumulates special secondary metabolites with a wide range of pharmacological effects for surviving in drought and high salty areas, while researchers focused more on their environmental adaptations and evolutions. Nevadensin (5,7-dihydroxy-6,8,4'-trimethoxyflavone), the main active component in L. pauciflours, has unique bioactivity of such as anti-inflammatory, anti-tubercular, and anti-tumor or cancer. Complex decoration of nevadensin, such as hydroxylation and glycosylation of the flavone skeleton determines its diversity and biological activities. The lack of omics data limits the exploration of accumulation mode and biosynthetic pathway. Herein, we integrated transcriptomics, metabolomics, and microbial recombinant protein system to reveal hydroxylation and glycosylation involving nevadensin biosynthesis in L. pauciflours.

Results

Up to 275 flavonoids were found to exist in L. pauciflorus by UPLC-MS/MS based on widely targeted metabolome analysis. The special flavone nevadensin (5,7-dihydroxy-6,8,4'-trimethoxyflavone) is enriched in different tissues, as are its related glycosides. The flavonoid biosynthesis pathway was drawn based on differential transcripts analysis, including 9 PAL, 5 C4H, 8 4CL, 6 CHS, 3 CHI, 1 FNSII, and over 20 OMTs.

Total 310 LpCYP450s were classified into 9 clans, 36 families, and 35 subfamilies, with 56% being A-type CYP450s by phylogenetic evolutionary analysis. According to the phylogenetic tree with AtUGTs, 187 LpUGTs clustered into 14 evolutionary groups (A-N), with 74% being E, A, D, G, and K groups.

Two LpCYP82D members and LpUGT95 were functionally identified in Saccharomyces cerevisiae and Escherichia coli, respectively. CYP82D-8 and CYP82D-1 specially hydroxylate the 6- or 8-position of A ring in vivo and in vitro, dislike the function of F6H or F8H discovered in basil which functioned depending on A-ring substituted methoxy. These results refreshed the starting mode that apigenin can be firstly hydroxylated on A ring in nevadensin biosynthesis. Furthermore, LpUGT95 clustered into the 7-OGT family was verified to catalyze 7-O glucosylation of nevadensin accompanied with weak nevadensin 5-O glucosylation function, firstly revealed glycosylation modification of flavones with completely substituted A-ring.

Conclusions

Metabolomic and full-length transcriptomic association analysis unveiled the accumulation mode and biosynthetic pathway of the secondary metabolites in the karst-adapted plant L. pauciflorus. Moreover, functional identification of two LpCYP82D members and one LpUGT in microbe reconstructed the pathway of nevadensin biosynthesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01921-2.

Thermal Control Using Far-Infrared Irradiation for Producing Deglycosylated Bioactive Compounds from Korean Ginseng Leaves

Although ginseng leaf is a good source of health-beneficial phytochemicals, such as polyphenols and ginsenosides, few studies have focused on the variation in compounds and bioactivities during leaf thermal processing. The efficiency of far-infrared irradiation (FIR) between 160 °C and 200 °C on the deglycosylation of bioactive compounds in ginseng leaves was analyzed. FIR treatment significantly increased the total polyphenol content (TPC) and kaempferol production from panasenoside conversion. The highest content or conversion ratio was observed at 180 °C (FIR-180). Major ginsenoside contents gradually decreased as the FIR temperature increased, while minor ginsenoside contents significantly increased. FIR exhibited high efficiency to produce dehydrated minor ginsenosides, of which F4, Rg6, Rh4, Rk3, Rk1, and Rg5 increased to their highest levels at FIR-190, by 278-, 149-, 176-, 275-, 64-, and 81-fold, respectively. Moreover, significantly increased antioxidant activities were also observed in FIR-treated leaves, particularly FIR-180, mainly due to the breakage of phenolic polymers to release antioxidants. These results suggest that FIR treatment is a rapid and efficient processing method for producing various health-beneficial bioactive compounds from ginseng leaves. After 30 min of treatment without leaf burning, FIR-190 was the optimum temperature for producing minor ginsenosides, whereas FIR-180 was the optimum temperature for producing polyphenols and kaempferol. In addition, the results suggested that the antioxidant benefits of ginseng leaves are mainly due to polyphenols rather than ginsenosides.

Unraveling the Glucosylation of Astringency Compounds of Horse Chestnut via Integrative Sensory Evaluation, Flavonoid Metabolism, Differential Transcriptome, and Phylogenetic Analysis

The seeds of Chinese horse chestnut are used as a source of starch and escin, whereas the potential use of whole plant has been ignored. The astringency and bitterness of tea produced from the leaves and flowers were found to be significantly better than those of green tea, suggesting that the enriched flavonoids maybe sensory determinates. During 47 flavonoids identified in leaves and flowers, seven flavonol glycosides in the top 10 including astragalin and isoquercitrin were significantly higher content in flowers than in leaves. The crude proteins of flowers could catalyze flavonol glucosides' formation, in which three glycosyltransferases contributed to the flavonol glucosylation were screened out by multi-dimensional integration of transcriptome, evolutionary analyses, recombinant enzymatic analysis and molecular docking. The deep exploration for flavonol profile and glycosylation provides theoretical and experimental basis for utilization of flowers and leaves of Aesculus chinensis as additives and dietary supplements.

Identification and Characterization of Glucosyltransferase That Forms 1-Galloyl-β-d-Glucogallin in Canarium album L., a Functional Fruit Rich in Hydrolysable Tannins

Hydrolysable tannins (HTs) are useful secondary metabolites that are responsible for pharmacological activities and astringent taste, flavor, and quality in fruits. They are also the main polyphenols in Canarium album L. (Chinese olive) fruit, an interesting and functional fruit that has been cultivated for over 2000 years. The HT content of C. album fruit was 2.3-13 times higher than that of berries with a higher content of HT. 1-galloyl-β-d-glucose (βG) is the first intermediate and the key metabolite in the HT biosynthesis pathway. It is catalyzed by UDP-glucosyltransferases (UGTs), which are responsible for the glycosylation of gallic acid (GA) to form βG. Here, we first reported 140 UGTs in C. album. Phylogenetic analysis clustered them into 14 phylogenetic groups (A, B, D-M, P, and Q), which are different from the 14 typical major groups (A~N) of Arabidopsis thaliana. Expression pattern and correlation analysis showed that UGT84A77 (Isoform0117852) was highly expressed and had a positive correlation with GA and βG content. Prokaryotic expression showed that UGT84A77 could catalyze GA to form βG. These results provide a theoretical basis on UGTs in C. album, which will be helpful for further functional research and availability on HTs and polyphenols.