Jul 2026· International Journal of Biological Macromolecules· Vol 376, pp.
153396
· 0 citations· 76 references
Medicine
TL;DR
It is shown that the expression of arGST gene in bilberry increases during fruit ripening in parallel with other ABP genes and putative transcription factors and revealed a possible inhibitory effect of quercetin on arGST activity, as quercetin is a by-product of the anthocyanin biosynthetic pathway.
Abstract
The anthocyanin biosynthetic pathway (ABP), a branch of the phenylpropanoid pathway, is responsible for the production of a wide range of flavonoid compounds in plants. Anthocyanin-related glutathione transferases (arGSTs) have long been proposed to act as non-catalytic carrier proteins, mediating the vacuolar sequestration of anthocyanins. However, recent structural and biochemical evidence has suggested a potential catalytic role for arGSTs in the ABP, notably in catalyzing the dehydration of flavan-3,3,4-triol to anthocyanidin. Despite their importance, only a limited number of arGSTs have been characterized biochemically and structurally. Here, we investigated the arGST isoform from bilberry, one of the richest fruit sources of anthocyanins. We showed that the expression of arGST gene in bilberry increases during fruit ripening in parallel with other ABP genes and putative transcription factors. Biochemical and structural analyses highlighted the remarkable ability of GSTs to adapt to their substrates and revealed a possible inhibitory effect of quercetin on arGST activity, as quercetin is a by-product of the anthocyanin biosynthetic pathway.
This comprehensive analysis provides a solid theoretical and practical basis for optimizing CHS function and flavonoid biosynthesis, facilitating the sustainable development and practical implementation of industrial and agricultural applications of these bioactive compounds.
Yongxing Chen, Caiyan Liang, Yijing Liu et al.· Journal of Experimental Bota...· 0 citations
Flavonoids are polyphenolic natural products predominantly isolated from plants and exhibit a diverse array of biological activities. Because they serve as important pharmaceuticals and nutraceuticals, there is a strong demand for their sustainable supply. Chlorflavonin is a rare fungal flavonoid with potent antitubercular activity. While its biosynthetic enzymes are expected to be valuable tools for application in fungal production of flavonoids, the biosynthetic pathway remains unknown. Here, we elucidate the complete biosynthetic pathway for chlorflavonin through detailed functional analysis of each biosynthetic enzyme. Previously, stepwise and straightforward introduction of 3-, 7-, and 8-methoxy; 2'-hydroxy; and 3'-chloro functionalities have been proposed. In contrast to this proposal, we uncovered an intricate biosynthetic route involving a dynamic interconversion between the 6- and 8-methoxy forms of flavonoid skeletons mediated by the chalcone isomerase CfvF and the flavin-dependent oxygenase CfvI. CfvF interconverted the 6- and 8-methoxyflavanones, likely via a chalcone intermediate. CfvI oxidized the chemically inert 2,3-double bond of flavanone, giving the hemiacetal product. Although these enzymes generate products existing in equilibrium states, respective downstream enzymes catalyze selective conversion of one specific species, facilitating smooth progression to the final product. We also solved the crystal structure of CfvK, the dehydratase that selectively converts the 8-methoxy form of the CfvI product. Through analyzing the structure complexed with its substrate and product and site-directed mutagenesis, key residues determining the substrate selectivity were identified. Our comprehensive analysis established a rational framework for preparing 46 flavonoids, including unnatural ones, setting the stage for fungal production of structurally diverse flavonoids.
Sho Furumura, T. Ozaki, Kazuya Hasegawa et al.· Journal of the American Chem...· 0 citations
As a core family of hormone regulating plant growth and development, the biosynthesis and inactivation mechanisms of cytokinins (CKs) have been well studied in plants. However, these processes remain largely uncharacterized in other organisms, particularly fungal phytopathogens. Here, we identify a distinct pathway of CKs from Fusarium and unravel the chemical and enzymatic logic of biosynthesis and inactivation, which mainly includes: (1) the IPT-LOG fusion enzyme FexA catalyzes N6-dimethylallylation of AMP and cleavage of the C1″-N9 bond to form iP (1); (2) the CYP450 FexB not only hydroxylates 1 to generate the canonical plant-type CKs trans-zeatin (tZ, 2) and cis-zeatin (cZ, 3), but also sequentially catalyzes C4'-N6 cyclization to produce a pyrrole derivative (6); (3) the BBE-like oxidase FexC independently mediates oxidative cleavage of compounds 1-3 and unexpectedly converts 1 to C1'-keto-iP (16); (4) FexC and the NmrA-like SDR FexD cooperate to catalyze double bond isomerization, yielding two novel CKs (17 and 19), where FexD functions as a rare NADPH-dependent 1,4-reductase. Biological activity assays demonstrate that the noncanonical fungus-specific compounds 6, 17, and 19 represent new inactive CK forms for plants, whereas 16 exhibits unexpectedly high activity. Importantly, unlike plants, Fusarium employ double bond isomerization and pyrrole formation as novel strategies for CK inactivation. Our findings uncover unusual functions of fungal CK enzymes and reveal the molecular basis underlying CK biosynthesis and inactivation in plant pathogenic fungi, which provide new insights into the discovery and application of CK derivatives.
Jin-Mei Zhang, Guan-Yin Yuan, Qing-Dong Xu et al.· Journal of the American Chem...· 0 citations
Flavonoids, particularly galloylated catechins, are known to regulate pollen tube growth, but their mode of action in woody plants remains poorly characterized. Here, we investigated the effects of epigallocatechin gallate (EGCG) $\hbox{---}$a major galloylated catechin$\hbox{---}$ on Camellia oleifera pollen tubes using combined cytological and transcriptomic approaches. In vitro treatment with 100 $$g/mL EGCG significantly reduced pollen germination and tube elongation. Confocal and fluorescence microscopy revealed that EGCG rapidly disrupted the apical Ca2+ gradient within 10 min, accompanied by disorganized actin filaments and altered distribution of methyl-esterified pectin at the tube apex. Transcriptome profiling and antisense oligonucleotide (AS-ODN)-mediated knockdown identified a Rho GTPase-activating protein (ROPGAP6)-centered regulatory network associated with growth inhibition. Weighted gene co-expression network analysis (WGCNA) and subsequent AS-ODN knockdown experiments further revealed transcriptional coordination among Decapping protein 1 (Dcp1), small heat shock factor (sHSF), and ROPGAP6 in response to EGCG treatment. Collectively, our findings offer a multi-level framework for understanding how galloylated catechins regulate pollen tube growth in C. oleifera, providing insights into their roles in male reproduction of trees.
Honggang Xu, Jinming Feng, Xiaoying Li et al.· Tree Physiology· 0 citations
Based on the excellent fungicidal activity of the rosin-based Schiff derivative, compound 3c (Co. 3c), against Rhizoctonia solani, this study further investigated its action mechanism via multiomics, computer-aided drug design, phenotype, and physiological indicators. Transcriptomic and proteomic analyses identified 2010 differentially expressed genes (DEGs) and 311 differentially expressed proteins (DEPs), respectively. Steroid biosynthesis was the most significantly enriched pathway, and the DEGs and DEPs involved in sterol biosynthesis were simultaneously upregulated. DFT calculations revealed that Co. 3c exhibited high chemical reactivity, enabling stable noncovalent interactions with biomacromolecules. Mycelial phenotypic observations and physiological measurements confirmed that Co. 3c disrupted mycelial cellular structures, induced lipid peroxidation, and reduced the intracellular ergosterol content by 45.0%. Molecular docking suggested that Co. 3c bound to the active pockets of C-8 sterol isomerase and sterol 22-desaturase through hydrogen bonds and hydrophobic interactions. Collectively, these findings provide a theoretical basis for the development of rosin-derived fungicides.
Unknown authors· Journal of Agricultural and...· 0 citations
The seeds of Astragalus complanatus R. Br. (SAC), a medicinal food homologous resource, are widely distributed and utilized in China. A phytochemical investigation of the seeds of SAC afforded 47 flavonoids, including eight previously undescribed ones, designated as complanatin A (2), and neocomplanatosides A-G (38, 39, and 43-47). Among them, 43 and 44 are phenylpropanoid-esterified flavonoid glycosides, while 45-47 represent a rare class of sesquiterpene-esterified flavonoid glycosides. Their structures were elucidated by the NMR and HRESIMS spectroscopic data, and ECD calculations. Biological evaluation demonstrated that rhamnocitrin (15) inhibited ferroptosis in erastin-induced HT22 cells (EC50 = 7.79 ± 0.44 μM) by suppressing NOX4 expression and activating the SLC7A11/Nrf2 pathway. Molecular dynamics simulations confirmed its stable binding to NOX4 (RMSD < 0.4 nm; ΔGbind = - 47.92 kJ/mol), and competitive inhibition with GLX351322 further confirmed NOX4 as the direct target. These findings indicate that flavonoids from SAC, particularly rhamnocitrin (15), are promising natural neuroprotective candidates for food-based health applications.
