Identification and Functional Characterization of UDP-Glycosyltransferases Involved in Isoflavone Biosynthesis in Astragalus membranaceus

Biosynthesis and metabolic engineering of natural sweeteners

Natural sweeteners have attracted widespread attention because they are eco-friendly, healthy, low in calories, and tasty. The demand for natural sweeteners is increasing together with the popularity of green, low-carbon, sustainable development. With the development of synthetic biology, microbial cell factories have emerged as an effective method to produce large amounts of natural sweeteners. This technology has significantly progressed in recent years. This review summarizes the pathways and the enzymes related to the biosynthesis of natural sweeteners, such as mogrosides, steviol glycosides, glycyrrhizin, glycyrrhetinic acid, phlorizin, trilobatin, erythritol, sorbitol, mannitol, thaumatin, monellin, and brazzein. Moreover, it focuses on the research about the microbial production of these natural sweeteners using synthetic biology methods, aiming to provide a reference for future research on the production of natural sweeteners.

Overexpressing of GT8 confers resistance to fenoxaprop-P-ethyl in Alopecurus japonicus

BACKGROUND

Alopecurus japonicus is one of the most predominant weeds in wheat fields across China, where significant herbicide resistance has emerged over the past decade.

RESULTS

When compared to the susceptible (S) population, the resistant (R) population exhibited a 9.48-fold increase in resistance to fenoxaprop-P-ethyl. The R population displayed cross-resistance to haloxyfop-P-methyl, quizalofop-P-ethyl, clodinafop-propargyl, sethoxydim, clethodim and pinoxaden. No known resistance mutations or overexpression of ACCase were detected in the R population. The R population showed enhanced metabolism of fenoxaprop-P-ethyl, as evidenced by high-performance liquid chromatography analysis. The cytochrome P450 (CYP450) inhibitor malathion and the glutathione-S-transferase (GST) inhibitor 4-chloro-7-nitrobenzoxadiazole (NBD-Cl) partially reversed resistance to fenoxaprop-P-ethyl in the R population. Six upregulated genes were identified via RNA-sequencing, including two CYP450 genes (CYP86B1 and CYP71C1), one GST gene (GSTT1) and three glycosyl transferase (GT) genes (UGT73C, GT8 and CGT). Specifically, the expression of GT8 in yeast decreased sensitivity to fenoxaprop-P-ethyl, suggesting its potential involvement in herbicide metabolism. Molecular docking analysis further suggests that GT8 may be involved in herbicide metabolism.

CONCLUSION

Our findings not only identified GT8 as partially responsible for the resistance of A. japonicus to fenoxaprop-P-ethyl, but also provide a valuable resource for crop genetic engineering. These insights also could inform the development of effective management strategies for A. japonicus. © 2025 Society of Chemical Industry.

New flavonoid glycosides from the stems and leaves of Astragalus membranaceus

Astragalus membranaceus, a well-known traditional medicine and food, has been extensively studied for its roots. However, comparatively little attention has been paid to its stems and leaves. In this study, we successfully isolated and identified three new flavonoid glycosides (1-3), and eight known analogues (4-11) from the stems and leaves of A. membranaceus. Notably, compound 10 exhibited significant anti-inflammatory activities in LPS-induced BV2 cells, with IC50 value of 1.11 ± 0.04 μM. These findings highlight flavonoids as the key bioactive components present in the stems and leaves of A. membranaceus.

Comparative Metabolome and Transcriptome Analysis Revealed the Accumulative Mechanism of Rubusoside in Chinese Sweet Tea

Terpenoids are important secondary metabolites in Rubus. Rubusoside is a relatively specific diterpenoid bioactive component in the leaves of Chinese Sweet Tea (Rubus suavissimus). However, the terpenoid anabolic pathway of Rubus and the molecular mechanism underlying the specific accumulation of rubusoside in R. suavissimus remain unclear. Here, metabolomics and transcriptomics analyses were performed on differences in terpenoid metabolism levels between R. suavissimus (sweet leaves) and Rubus chingii (bitter leaves). Steviol glycosides and goshonosides primarily accumulated in R. suavissimus and R. chingii, respectively. Three pairs of highly homologous glycosyltransferase genes (UGT85A57, UGT75L20, and UGT75T4) associated with rubusoside biosynthesis in the two Rubus species were identified. The three pairs of UGT proteins in both species could glycosylate steviol. Thus, the transcriptional regulation of UGTs in R. suavissimus appears to play a pivotal role in rubusoside accumulation. Our findings provide insights into the differences in terpenoid metabolism between R. suavissimus and R. chingii and reveal the molecular mechanism of rubusoside accumulation in R. suavissimus.

An efficient flavonoid glycosyltransferase NjUGT73B1 from Nardostachys jatamansi of alpine Himalayas discovered by structure-based protein clustering

Tilianin and linarin, two rare glycosylated flavonoids in the aromatic endangered medicinal plant Nardostachys jatamansi (D.on)DC., play an important role in the fields of medicine, cosmetics, food and dye industries. However, there remains a lack of comprehensive understanding regarding their biosynthetic pathway. In this study, the phytochemical investigation of N. jatamansi resulted in the isolation of linarin. With help of AlphaFold2 to cluster the entire glycosyltransferase family based on predicted structure similarities, we successfully identified a flavonoid glycosyltransferase NjUGT73B1, which could efficiently catalyze the glucosylation of acacetin at 7-OH to produce tilianin, also the key precursor in the biosynthesis of linarin. Additionally, NjUGT73B1 displayed a high degree of substrate promiscuity, enabling glucosylation at 7-OH of many flavonoids. Molecular modeling and site-directed mutagenesis revealed that H19, H21, H370, F126, and F127 play the crucial roles in the glycosylation ability of NjUGT73B1. Notably, comparation with the wild NjUGT73B1, mutant H19K led to a 50% increase in the activity of producing tilianin from acacetin.

Enhancing rutin accumulation in Tartary buckwheat through a novel flavonoid transporter protein FtABCC2

Tartary buckwheat (Fagopyrum tataricum) is an annual coarse cereal from the Polygonaceae family, known for its high content of flavonoid compounds, particularly rutin. But so far, the mechanisms of the flavonoid transport and storage in Tartary buckwheat (TB) remain largely unexplored. This study focuses on ATP-binding cassette transporters subfamily C (ABCC) members, which are crucial for the biosynthesis and transport of flavonoids in plants. The evolutionary and expression pattern analyses of the ABCC genes in TB identified an ABCC protein gene, FtABCC2, that is highly correlated with rutin synthesis. Subcellular localization analysis revealed that FtABCC2 protein is specifically localized to the vacuole membrane. Heterologous expression of FtABCC2 in Saccharomyces cerevisiae confirmed that its transport ability of flavonoid glycosides such as rutin and isoquercetin, but not the aglycones such as quercetin and dihydroquercetin. Overexpression of FtABCC2 in TB hairy root lines resulted in a significant increase in total flavonoid and rutin content (P < 0.01). Analysis of the FtABCC2 promoter revealed potential cis-acting elements responsive to hormones, cold stress, mechanical injury and light stress. Overall, this study demonstrates that FtABCC2 can efficiently facilitate the transport of rutin into vacuoles, thereby enhancing flavonoids accumulation. These findings suggest that FtABCC2 is a promising candidate for molecular-assisted breeding aimed at developing high-flavonoid TB varieties.

An evaluation of Astragali Radix with different growth patterns and years, based on a new multidimensional comparison method

Introduction

With the depletion of wild Astragali Radix (WA) resources, imitated-wild Astragali Radix (IWA) and cultivated Astragali Radix (CA) have become the main products of Astragali Radix. However, the quality differences of three growth patterns (WA, IWA, CA) and different growth years of Astragali Radix have not been fully characterized, leading to a lack of necessary scientific evidence for their use as substitutes for WA.

Methods

We innovatively proposed a multidimensional evaluation method that encompassed traits, microstructure, cell wall components, saccharides, and pharmacodynamic compounds, to comprehensively explain the quality variances among different growth patterns and years of Astragali Radix.

Results and discussion

Our study showed that the quality of IWA and WA was comparatively similar, including evaluation indicators such as apparent color, sectional structure and odor, thickness of phellem, diameter and number of vessels, morphology of phloem and xylem, and the levels and ratios of cellulose, hemicellulose, lignin, sucrose, starch, water-soluble polysaccharides, total-saponins. However, the content of sucrose, starch and sorbose in CA was significantly higher than WA, and the diameter and number of vessels, total-flavonoids content were lower than WA, indicating significant quality differences between CA and WA. Hence, we suggest that IWA should be used as a substitute for WA instead of CA. As for the planting years of IWA, our results indicated that IWA aged 1-32 years could be divided into three stages according to their quality change: rapid growth period (1-5 years), stable growth period (6-20 years), and elderly growth period (25-32 years). Among these, 6-20 years old IWA exhibited consistent multidimensional comparative results, showcasing elevated levels of key active components such as water-soluble polysaccharides, flavonoids, and saponins. Considering both the quality and cultivation expenses of IWA, we recommend a cultivation duration of 6-8 years for growers. In conclusion, we established a novel multidimensional evaluation method to systematically characterize the quality of Astragali Radix, and provided a new scientific perspective for the artificial cultivation and quality assurance of Astragali Radix.