Flavonol Biosynthesis Research Articles

Elucidation of the key pathway for flavonol biosynthesis in golden Camellia and its application in genetic modification of tomato fruit metabolism

Elucidation of the key pathway for flavonol biosynthesis in golden <i>Camellia</i> and its application in genetic modification of tomato fruit metabolism

The impact of different lactobacilli fermentations on secondary metabolites of red raspberry juice and their biotransformation pathways via metabolomics based on UHPLC-MS/MS

Secondary metabolites are a group of invaluable phytochemicals in raspberries. Fermentation process leads to changes in the phytochemical composition of fruits. This study aimed to investigate the influence of Lacticaseibacillus paracasei subsp. paracasei FBKL1.0328 and Lactiplantibacillus plantarum subsp. plantarum FBKL1.0310 on the secondary metabolites of red raspberry juice (CR) and uncover their conversion pathways via metabolomics based on ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). A total of 695 secondary metabolites in the unfermented and fermented samples were identified. There were 90, 83 and 52 differential secondary metabolites identified in LCR (L. paracasei FBKL1.0328 fermented raspberry juice) vs. CR, LPR (L. plantarum FBKL1.0310 fermented raspberry juice) vs. CR, and LCR vs. LPR, respectively. Certain phenolic acids (e.g. 3-phenyllacitc acid), flavonoids (e.g. galangin-7-glucoside), alkaloids (e.g. indole-3-lactic acid), and terpenoids (e.g. glucosyl 7-methyl-3-methyleneoctane-1,2,6,7-tetraol) were selected as the crucial differential metabolites. These two lactobacilli utilized distinct metabolic pathways for processing secondary metabolites. L. paracasei FBKL1.0328 primarily transformed flavonoids through the “Flavone and flavonol biosynthesis” pathway. L. plantarum FBKL1.0310 mainly converted phenolic acids via the “Tyrosine metabolism” pathway and the “Aminobenzoate degradation” pathway. Interestingly, L. plantarum FBKL1.0310 outperformed L. paracasei FBKL1.0328 in upregulating certain valuable bioactive compounds such as indole-3-lactic acid and 3-phenyllacitc acid, underscoring its potential as a promising strain for developing health-beneficial fermented fruit juices. These findings provide insights to how different lactobacilli modify secondary metabolite composition in red raspberry juice and offer valuable information for the industrial application of lactobacilli in fruit processing.

VviMYB24 positively regulates flavonol biosynthesis in response to moderate drought stress in ‘Cabernet Sauvignon’ grape seedlings

Drought is a kind of adversity that has always severely restricted the growth of grapes. Flavonols, as flavonoid compounds, are abundant in grapes and have an indispensable function in resisting drought. Hereafter, the objectives of this investigation were to identify key drought-induced transcription factors in grape and explore their roles and regulatory networks in the flavonol-mediated drought response mechanism. In this study, one-year-old cutting seedlings of ‘Cabernet Sauvignon’ grape were used as experimental materials, cultivated in a solar greenhouse, and subjected to moderate drought treatment. The physiological and biochemical parameters related to stress and flavonol content in plant tissues were determined, and gene expression, functional validation, and transcriptional regulation relationships were explored. The results showed that the growth of grape plants was affected under drought conditions, the flavonol accumulation and the expression level of VviMYB24 were significantly induced by drought stress. Overexpression of VviMYB24 reduced the degree of cytoplasmic membrane damage and induced flavonol biosynthesis to confer drought tolerance in Arabidopsis plants and grape callus. Further study revealed that VviMYB24 can interact with the bHLH transcription factor VviMYC2b, which was positively responsive to drought, and they could activate VviFLS5 expression individually and/or in combination in the form of a complex. Interestingly, VviMYB24 could positively regulate VviMYC2b expression to form a transcriptional cascade, enhancing the function of the complex. Transient overexpression of VviMYB24, VviMYC2b, and VviFLS5 in grape leaves promoted the drought-responsive flavonol accumulation. Overall, the above data elucidated that the VviMYB24-VviMYC2b-VviFLS5 module positively regulates drought-induced flavonol biosynthesis in response to drought stress in grape, which contributes to further grape drought resistant breeding and variety improvement through biotechnology.

LncNAT11-GbMYB11-GbF3'H/GbFLS module mediates flavonol biosynthesis to regulate salt stress tolerance in Ginkgo biloba.

Flavonols are important secondary metabolites that enable plants to resist environmental stresses. Although MYB regulation of flavonol biosynthesis has been well studied, the lncRNA-MYB networks involved in regulating flavonol biosynthesis remain unknown. Ginkgo biloba is rich in flavonols, which are the most important medicinal components. Based on multi-omics data and phylogenetic trees, we identified GbMYB11 as a potential key transcription factor regulating flavonol biosynthesis. Overexpression and VIGS experiments confirmed that GbMYB11 acts as a pivotal positive regulator in flavonol biosynthesis. In the transcriptome of calli overexpressing GbMYB11, we identified significant upregulation of GbF3'H and GbFLS in the flavonol biosynthetic pathway. Yeast one-hybrid and dual-luciferase assays demonstrated that GbMYB11 enhances the expression of GbF3'H and GbFLS by binding to their promoters. Interestingly, we identified LncNAT11, an antisense lncRNA complement to GbMYB11, which negatively regulates flavonol biosynthesis by repressing the expression of GbMYB11. Consequently, we established the LncNAT11-GbMYB11-GbF3'H/GbFLS module as a critical regulator of flavonol biosynthesis in G. biloba, and further elucidated that this module can mitigate the accumulation of reactive oxygen species by modulating flavonol biosynthesis during salt stress. These findings unveil a novel mechanism underlying flavonol biosynthesis and a lncRNA-MYB mediated salt stress tolerance strategy in plants.

Arbuscular mycorrhizal fungi and intercropping Vicia villosa mediate plant biomass, soil properties, and rhizosphere metabolite profiles of walnuts

Intercropping is a prevalent soil management strategy within orchards, whereas it is unclear how inoculation with arbuscular mycorrhizal (AM) fungi and intercropping affect tree growth, soil properties, and rhizosphere metabolite profiles. This study investigated the effects of inoculation with Diversispora spurca and intercropping with hairy vetch (Vicia villosa) on biomass production, soil available nutrients, water-stable aggregate (WSA) distribution, phosphatase activity, and secondary metabolite profiles in walnuts (Juglans regia). The intercropping only elevated soil nitrate N levels and WSA distribution at the 0.5–2 mm size, and also triggered 2159 differential metabolites (1378 up-regulated and 781 down-regulated), with armillaramide as the most prominently up-regulated metabolite, followed by the substance diminished upon D. spurca inoculation. Conversely, D. spurca inoculation increased walnut biomass, WSA distribution across the 0.25 − 2 mm size, and acid and neutral phosphatase activities, as well as triggered 2489 differential metabolites (897 up-regulated and 1592 down-regulated), with pteroside D being highest up-regulated differential metabolite, allowing a competitive advantage to AM plants in combating soil pathogens. Despite significantly suppressing root AM fungal colonization and biomass production in AM walnuts, intercropping significantly increased soil ammonium and nitrate N levels in AM walnuts as well as WSAs at the 1–4 mm size, exhibiting a synergistic effect. Flavone and flavonol biosynthesis and pyruvate metabolism were simultaneously involved following AM inoculation or intercropping. Co-application of AM inoculation and intercropping triggered 1006 differential metabolites, with urocanic acid being the most up-regulated metabolite, although it decreased following AM inoculation, suggesting the involvement of mycorrhizal hyphae in soil histidine uptake. Under intercropping, AM inoculation elicited 418 differential metabolites, with the most up-regulated metabolite being implicated in flavonoid pathways. AM inoculation primarily triggered the biosynthesis of unsaturated fatty acids, regardless of intercropping or not, implying a potential increase in unsaturated fatty acid contents of walnut kernels. It concluded that AM inoculation and intercropping interactively affected walnut growth, soil attributes, and soil microenvironment.Graphical

A Mycorrhiza-Induced UDP-Glucosyl Transferase Negatively Regulates the Arbuscular Mycorrhizal Symbiosis.

Most terrestrial plants can establish a reciprocal symbiosis with arbuscular mycorrhizal (AM) fungi to cope with adverse environmental stresses. The development of AM symbiosis is energetically costly and needs to be dynamically controlled by plants to maintain the association at mutual beneficial levels. Multiple components involved in the autoregulation of mycorrhiza (AOM) have been recently identified from several plant species; however, the mechanisms underlying the feedback regulation of AM symbiosis remain largely unknown. Here, we report that AM colonization promotes the flavonol biosynthesis pathway in tomato (Solanum lycopersicum), and an AM-specific UDP-glucosyltransferase SlUGT132, which probably has the flavonol glycosylation activity, negatively regulates AM development. SlUGT132 was predominantly expressed in the arbuscule-containing cells, and its knockout or knockdown mutants showed increased soluble sugar content, root colonization level and arbuscule formation. Conversely, overexpression of SlUGT132 resulted in declined soluble sugar content and mycorrhization degree. Metabolomic assay revealed decreased contents of astragalin, tiliroside and cynaroside in slugt132 mycorrhizal roots, but increased accumulation of these flavonoid glycosides in SlUGT132-overexpressing plant roots. Our results highlight the presence of a novel, SlUGT132-mediated AOM mechanism, which enable plants to flexibly control the accumulation of soluble sugars and flavonoid glycosides in mycorrhizal roots and modulate colonization levels.

Metabolic pathways regulated by strigolactones foliar spraying enhance osmoregulation and antioxidant defense in drought-prone soybean

BackgroundDrought stress is a significant abiotic stressor that hinders growth, development, and crop yield in soybeans. Strigolactones (SLs) positively regulate plant resistance to drought stress. However, the impact of foliar application of SLs having different concentrations on soybean growth and metabolic pathways related to osmoregulation remains unknown. Therefore, to clarify the impact of SLs on soybean root growth and cellular osmoregulation under drought stress, we initially identified optimal concentrations and assessed key leaf and root indices. Furthermore, we conducted transcriptomic and metabolic analyses to identify differential metabolites and up-regulated genes.ResultsThe results demonstrated that drought stress had a significant impact on soybean biomass, root length, root surface area, water content and photosynthetic parameters. However, when SLs were applied through foliar application at appropriate concentrations, the accumulation of ABA and soluble protein increased, which enhanced drought tolerance of soybean seedlings by regulating osmotic balance, protecting membrane integrity, photosynthesis and activating ROS scavenging system. This also led to an increase in soybean root length, lateral root number and root surface area. Furthermore, the effects of different concentrations of SLs on soybean leaves and roots were found to be time-sensitive. However, the application of 0.5 µM SLs had the greatest beneficial impact on soybean growth and root morphogenesis under drought stress. A total of 368 differential metabolites were screened in drought and drought plus SLs treatments. The up-regulated genes were mainly involved in nitrogen compound utilization, and the down-regulated metabolic pathways were mainly involved in maintaining cellular osmoregulation and antioxidant defenses.ConclusionsSLs enhance osmoregulation in soybean plants under drought stress by regulating key metabolic pathways including Arachidonic acid metabolism, Glycerophospholipid metabolism, Linoleic acid metabolism, and Flavone and flavonol biosynthesis. This study contributes to the theoretical understanding of improving soybean adaptability and survival in response to drought stress.

Sludge-derived biostimulants promote glycosylation of tricin and luteolin in the flavone and flavonol biosynthesis to enhance anti-inflammatory activities of rice

Alkaline thermal hydrolysis of sewage sludge produces nutrients and biostimulants that enhance plant growth, attracting considerable interest in agriculture. However, the metabolic differences and regulatory mechanisms of sewage sludge-derived biostimulants (SS-BS) on the phenotypic traits, nutritional quality, and safety indicators of harvested crops remain unclear. This study investigates the impact of SS-BS on rice quality on an agricultural production scale. The research reveals that rice treated with SS-BS complies with safety standards comparable to premium rice. SS-BS significantly enhances nutrient enrichment in the endosperm, increasing protein, vitamin B1, dietary fiber, and vitamin E content by 7%, 7.2%, 23.2%, and 42.2%, respectively. Furthermore SS-BS upregulates the FG2 gene,leading to increased Nictoflorin content and activation of the gene expression of UGT73C6 and CYP75A, which catalyze O-glycosylation and promot glycosyl transfer. By inhibiting the synthesis of Trifolin, Scolymoside, and Swertiajaponin, SS-BS favors the synthesis of glycosylated derivatives of Tricin and Luteolin, which exhibit higher anti-inflammatory activity. Additionally, two novel genes, novel.2100 and novel.1300, and an uncharacterized gene, LOC9269295, are closely associated with the production of anti-inflammatory and antioxidant compounds. This study provides new evidence for SS-BS application and insights into their regulatory mechanisms affecting crop quality, contributing to the development of functional foods and sustainable agriculture.

Evaluating of effects for the sequence fermentation with M. pulcherrima and I. terricola on mulberry wine fermentation: Physicochemical, flavonoids, and volatiles profiles

This study investigates the variation of physicochemical, flavonoids, and volatiles during sequential fermentation which Metschnikowia pulcherrima and Issatchenkia terricola as sequential co-fermenters and a single fermentation by Saccharomyces cerevisiae in mulberry wine. Sequential fermentation shown that β-glucosidase activity greater and fermentation time declined to 144 h. In addition, 11 flavonoids (apigenin-5-O-glucoside, aromadendrin-7-O-glucoside, kaempferol-3,7-O-diglucoside, and so on) were significantly increased. Significant differences were found between types of metabolic products enriched in flavone and flavonol biosynthesis and anthocyanins biosynthesis, with an enrichment ratio of 46.15 % and 23.08 %, respectively. 16 apple-scented compounds (2-Buten-1-one, (E)-1-(2,6,6-trimethyl-1,3-cyclohexadien-1-yl)-, Butanoic acid, (Z)-3-hexenyl ester, 3-methyl-1-methylethyl-Butanoic acid ester, and so on), 5 rose-scented (e.g. benzyl alcohol, ethyl geranate, hydrocinnamic acid), and 4 balsamic-scented compounds ((−)-myrtenol, benzoic acid 1-methylethyl ester, benzyl alcohol, p-cymen-7-ol) were distinctively present. Interestingly, tryptophan metabolism and indole alkaloid biosynthesis are only enriched in sequential fermentation.

Comparative transcriptomic and metabolomic analysis reveals mechanisms of selenium-regulated anthocyanin synthesis in waxy maize (Zea mays L.).

Anthocyanins in maize (Zea mays L.) kernels determine the plant's color and can enhance its resistance. Selenium (Se) significantly impacts plant growth, development, and secondary metabolic regulation. However, the molecular mechanisms by which Se regulates anthocyanin synthesis in waxy corn remain unclear. This study employed integrated transcriptomic and metabolomic analyses to investigate the mechanisms through which selenium influences anthocyanin synthesis in yellow and purple waxy corn. The results showed that maize varieties with higher anthocyanin content had higher selenium enrichment capacity in their kernels. Under selenium stress, HN2025 exhibited 1,904 more differentially expressed genes (DEGs) and 140 more differential metabolites compared to HN5. The expression levels of anthocyanin synthesis-related genes and transcription factors such as phenylalanine ammonia-lyase, flavonoid 3-hydroxylase (F3H), dihydroflavonol reductase (DFR), chalcone synthase (CHS), cinnamate-4-hydroxylase (C4H), anthocyanin 5,3-O-glucosyltransferases, and anthocyanidin reductase, MYB, and bHLH were strongly induced in HN2025. Metabolomic analysis revealed significant enrichment in anthocyanin biosynthesis, flavonoid and flavonol biosynthesis, glutathione metabolism, phenylalanine biosynthesis, and phenylalanine metabolism under selenium treatment. Three up-regulated PAL genes and one C4H gene were significantly enriched with DAMs in phenylalanine metabolism, phenylpropanoid biosynthesis, flavonoid biosynthesis, and anthocyanin biosynthesis, resulting in significant differences between HN5 and HN2025 in selenium-induced anthocyanin metabolism-related pathways. These findings provide a theoretical basis for understanding the effects of selenium on the molecular regulatory mechanisms of anthocyanin biosynthesis in maize kernels.

FtMYB163 Gene Encodes SG7 R2R3-MYB Transcription Factor from Tartary Buckwheat (Fagopyrum tataricum Gaertn.) to Promote Flavonol Accumulation in Transgenic Arabidopsis thaliana.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is a coarse grain crop rich in flavonoids that are beneficial to human health because they function as anti-inflammatories and provide protection against cardiovascular disease and diabetes. Flavonoid biosynthesis is a complex process, and relatively little is known about the regulatory pathways involved in Tartary buckwheat. Here, we cloned and characterized the FtMYB163 gene from Tartary buckwheat, which encodes a member of the R2R3-MYB transcription factor family. Amino acid sequence and phylogenetic analysis indicate that FtMYB163 is a member of subgroup 7 (SG7) and closely related to FeMYBF1, which regulates flavonol synthesis in common buckwheat (F. esculentum). We demonstrated that FtMYB163 localizes to the nucleus and has transcriptional activity. Expression levels of FtMYB163 in the roots, stems, leaves, flowers, and seeds of F. tataricum were positively correlated with the total flavonoid contents of these tissues. Overexpression of FtMYB163 in transgenic Arabidopsis enhanced the expression of several genes involved in early flavonoid biosynthesis (AtCHS, AtCHI, AtF3H, and AtFLS) and significantly increased the accumulation of several flavonoids, including naringenin chalcone, naringenin-7-O-glucoside, eriodictyol, and eight flavonol compounds. Our findings demonstrate that FtMYB163 positively regulates flavonol biosynthesis by changing the expression of several key genes in flavonoid biosynthetic pathways.

Delineating Molecular Regulatory of Flavonoids Indicated by Transcriptomic and Metabolomics Analysis during Flower Development in Chrysanthemum morifolium ‘Boju’

Flavonoids are pharmacologically active compounds in flowers of Chrysanthemum morifolium ‘Boju’ (C. morifolium); however, the molecular regulatory network governing flower development remains largely elusive. Flower samples were collected at four stages, namely budding (BD), bud breaking (BB), early blooming (EB), and full blooming (FB), for omics analysis. We revealed distinct transcriptional regulation patterns at these four stages of the flower from the perspective of differentially expressed unigenes (DEGs). There are 152 DEGs shared among the three comparative groups (BD vs. BB, BB vs EB, EB vs FB), wherein the expression of 44 DEGs (including AtADT6, MDL3, and ROMT) continues to be upregulated, and 85 DEGs (including CYP81E, TPS-Cin-1, and TPS-Cin-2) showed persistent downregulation with flower development. Flavonoid-targeted metabolomics identified 118 differentially abundant metabolites (DAMs) in the FB group compared to the BD stage; the top three upregulated and downregulated metabolites are Cyanidin-3-O-(6″-O-malonyl)glucoside-5-O-glucoside, Luteolin-7-O-(6″-caffeoyl)rhamnoside, Kaempferol-3-O-(6″-p-coumaroyl)glucoside and Chrysoeriol-6,8-di-C-glucoside-7-O-glucoside, Kaempferol, Kaempferol-3,7-O-dirhamnoside, respectively. These DAMs were predominantly enriched in “flavonoid biosynthesis”, “isoflavonoid biosynthesis”, and “flavone and flavonol biosynthesis” pathways. AtADT6, MDL3, ROMT, CYP81E, TPS-Cin-1, and TPS-Cin-2 were correlated with kaempferol. Our findings provide a new idea for interfering with flavonoid production, especially kaempferol, in flowers.

Multi-omics analysis revealed the mechanism underlying flavonol biosynthesis during petal color formation in Camellia Nitidissima

BackgroundCamellia nitidissima is a rare, prized camellia species with golden-yellow flowers. It has a high ornamental, medicinal, and economic value. Previous studies have shown substantial flavonol accumulation in C. nitidissima petals during flower formation. However, the mechanisms underlying the golden flower formation in C. nitidissima remain largely unknown.ResultsWe performed an integrative analysis of the transcriptome, proteome, and metabolome of the petals at five flower developmental stages to construct the regulatory network underlying golden flower formation in C. nitidissima. Metabolome analysis revealed the presence of 323 flavonoids, and two flavonols, quercetin glycosides and kaempferol glycosides, were highly accumulated in the golden petals. Transcriptome and proteome sequencing suggested that the flavonol biosynthesis-related genes and proteins upregulated and the anthocyanin and proanthocyanidin biosynthesis-related genes and proteins downregulated in the golden petal stage. Further investigation revealed the involvement of MYBs and bHLHs in flavonoid biosynthesis. Expression analysis showed that flavonol synthase 2 (CnFLS2) was highly expressed in the petals, and its expression positively correlated with flavonol content at all flower developmental stages. Transient overexpression of CnFLS2 in the petals increased flavonol content. Furthermore, correlation analysis showed that the jasmonate (JA) pathways positively correlated with flavonol biosynthesis, and exogenous methyl jasmonate (MeJA) treatment promoted CnFLS2 expression and flavonol accumulation.ConclusionsOur findings showed that the JA-CnFLS2 module regulates flavonol biosynthesis during golden petal formation in C. nitidissima.

Metabolomics Analysis of Phenolic Composition and Content in Five Pear Cultivars Leaves.

Phenolic compounds are the predominant chemical constituents in the secondary metabolites of plants and are commonly found in pears. In this study, we focused on the analysis of the phenolic composition and antioxidant activity of leaves from five pear cultivars (Cuiguan, Chaohong, Kuerle, Nanguoli, and Yali) and tea leaves (Fudingdabai as the control) using ultra-performance liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry. The results indicated significant differences in the amount and composition of phenolic metabolites between tea and pear leaves, as well as among the five pear varieties. Only approximately one-third of the metabolites exhibited higher levels in pear leaves compared to that in tea leaves. The total phenol content in the Yali cultivar was higher than that in the other pear cultivars. Furthermore, specific phenolic metabolites with high expression were identified in the leaves of different groups. The levels of delphinidin 3-glucoside, aesculin, prunin, cosmosiin, quercetin 3-galactoside, isorhamnetin-3-O-glucoside, nicotiflorin, narcissin, chlorogenic acid, and cryptochlorogenic acid were relatively high among the five pear cultivars. (-)-Gallocatechin gallate, 6-methylcoumarin, aesculetin, hesperidin, kaempferol, and caftaric acid were identified as specific metabolic substances unique to each type of pear leaf. Most of the differential metabolites showed positive correlations and were primarily enriched in the flavonoid biosynthesis, flavone and flavonol biosynthesis, and phenylpropanoid biosynthesis pathways. DPPH (1,1-Diphenyl-2-picrylhydrazyl radical) analysis indicated that the Yali cultivar exhibited the highest antioxidant activity compared to other varieties. This systematic analysis of the differences in phenolic metabolite composition and antioxidant activity between pear and tea leaves provides a theoretical foundation for the development and utilization of pear leaf resources.

Commonalities and Specificities in Wheat (Triticum aestivum L.) Responses to Aluminum Toxicity and Low Phosphorus Revealed by Transcriptomics and Targeted Metabolomics.

Aluminum (Al) toxicity and low phosphorus availability (LP) are the top two co-existing edaphic constraints limiting agriculture productivity in acid soils. Plants have evolved versatile mechanisms to cope with the two stresses alone or simultaneously. However, the specific and common molecular mechanisms, especially those involving flavonoids and carbohydrate metabolism, remain unclear. Laboratory studies were conducted on two wheat genotypes-Fielder (Al-tolerant and P-efficient) and Ardito (Al-sensitive and P-inefficient)-exposed to 50 μM Al and 2 μM Pi (LP) in hydroponic solutions. After 4 days of stress, wheat roots were analyzed using transcriptomics and targeted metabolomics techniques. In Fielder, a total of 2296 differentially expressed genes (DEGs) were identified under Al stress, with 1535 upregulated and 761 downregulated, and 3029 DEGs were identified under LP stress, with 1591 upregulated and 1438 downregulated. Similarly, 4404 DEGs were identified in Ardito under Al stress, with 3191 upregulated and 1213 downregulated, and 1430 DEGs were identified under LP stress, with 1176 upregulated and 254 downregulated. GO annotation analysis results showed that 4079 DEGs were annotated to the metabolic processes term. These DEGs were significantly enriched in the phenylpropanoid, flavonoid, flavone and flavonol biosynthesis, and carbohydrate metabolism pathways by performing the KEGG enrichment analysis. The targeted metabolome analysis detected 19 flavonoids and 15 carbohydrate components in Fielder and Ardito under Al and LP stresses. In Fielder, more responsive genes and metabolites were involved in flavonoid metabolism under LP than Al stress, whereas the opposite trend was observed in Ardito. In the carbohydrate metabolism pathway, the gene and metabolite expression levels were higher in Fielder than in Ardito. The combined transcriptome and metabolome analysis revealed differences in flavonoid- and carbohydrate-related genes and metabolites between Fielder and Ardito under Al and LP stresses, which may contribute to Fielder's higher resistance to Al and LP. The results of this study lay a foundation for pyramiding genes and breeding multi-resistant varieties.

Metabolite and Transcriptome Profiling Analysis Provides New Insights into the Distinctive Effects of Exogenous Melatonin on Flavonoids Biosynthesis in Rosa rugosa.

Although the petals of Rosa rugosa are rich in flavonoids and their bioactivity has a significant impact on human health, the flavonoid content decreases during flower development. In this study, R. rugosa 'Feng hua' was used to investigate the effects of the melatonin foliar spray on enhancing the quality of rose by focusing on major flavonoids. The results showed that the contents of total flavonoids in rose petals at the full bloom stage induced by melatonin obeyed a bell-shaped curve, with a maximum at 0.3 mM, indicating the concentration-dependent up-regulation of flavonoid biosynthesis. In the treatment with 0.3 mM melatonin, metabolomic analyses showed that the concentrations of ten main flavonoids were identified to be increased by melatonin induction, with high levels and increases observed in three flavonols and two anthocyanins. KEGG enrichment of transcriptomic analysis revealed a remarkable enrichment of DEGs in flavonoid and flavonol biosynthesis, such as Rr4CL, RrF3H, and RrANS. Furthermore, functional validation using virus-induced gene silencing technology demonstrated that Rr4CL3 is the crucial gene regulating flavonoid biosynthesis in response to the stimulant of melatonin. This study provides insights into the exogenous melatonin regulation mechanism of biosynthesis of flavonoids, thereby offering potential industrial applications.

Visual observation of polystyrene nano-plastics in grape seedlings of Thompson Seedless and assessing their effects via transcriptomics and metabolomics

Micro/nano-plastics (MNPs) are emerging non-point source pollutants that have garnered increasing attention owing to their threat to ecosystems. Studies on the effects of MNPs on horticultural crops are scarce. Specifically, whether MNPs can be absorbed and transported by grapevines have not been reported. To fill this gap, we added polystyrene nanoplastics (PS-NPs, 100 nm) to a hydroponic environment and observed their distribution in grape seedlings of Thompson Seedless (TS, Vitis vinifera L.). After 15 d of exposure, plastic nanospheres were detected on the cell walls of the roots, stems, and leaves using confocal microscopy and scanning electron microscopy. This indicated that PS-NPs can also be absorbed by the root system through the epidermis-cortex interface in grapevines and transported upward along the xylem conduit. Furthermore, we analyzed the molecular response mechanisms of TS grapes to the PS-NPs. Through the measurement of relevant indicators and combined omics analysis, we found that plant hormone signal transduction, flavonoid and flavonol biosynthesis, phenylpropanoid biosynthesis, and MAPK signaling pathway biosynthesis played crucial roles in its response to PS-NPs. The results not only revealed the potential risk of MNPs being absorbed by grapevines and eventually entering the food chain but also provided valuable scientific evidence and data for the assessment of plant health and ecological risk.

Synergistic actions of 3 MYB transcription factors underpin blotch formation in tree peony.

Blotches in floral organs attract pollinators and promote pollination success. Tree peony (Paeonia suffruticosa Andr.) is an internationally renowned cut flower with extremely high ornamental and economic value. Blotch formation on P. suffruticosa petals is predominantly attributed to anthocyanin accumulation. However, the endogenous regulation of blotch formation in P. suffruticosa remains elusive. Here, we identified the regulatory modules governing anthocyanin-mediated blotch formation in P. suffruticosa petals, which involves the transcription factors PsMYB308, PsMYBPA2, and PsMYB21. PsMYBPA2 activated PsF3H expression to provide sufficient precursor substrate for anthocyanin biosynthesis. PsMYB21 activated both PsF3H and PsFLS expressions and promoted flavonol biosynthesis. The significantly high expression of PsMYB21 in nonblotch regions inhibited blotch formation by competing for anthocyanin biosynthesis substrates, while conversely, its low expression in the blotch region promoted blotch formation. PsMYB308 inhibited PsDFR and PsMYBPA2 expressions to directly prevent anthocyanin-mediated blotch formation. Notably, a smaller blotch area, decreased anthocyanin content, and inhibition of anthocyanin structural gene expression were observed in PsMYBPA2-silenced petals, while the opposite phenotypes were observed in PsMYB308-silenced and PsMYB21-silenced petals. Additionally, PsMYBPA2 and PsMYB308 interacted with PsbHLH1-3, and their regulatory intensity on target genes was synergistically regulated by the PsMYBPA2-PsbHLH1-3 and PsMYB308-PsbHLH1-3 complexes. PsMYB308 also competitively bound to PsbHLH1-3 with PsMYBPA2 to fine-tune the regulatory network to prevent overaccumulation of anthocyanin in blotch regions. Overall, our study uncovers a complex R2R3-MYB transcriptional regulatory network that governs anthocyanin-mediated blotch formation in P. suffruticosa petals, providing insights into the molecular mechanisms underlying blotch formation in P. suffruticosa.

Integrated Analyses of Metabolome and RNA-seq Data Revealing Flower Color Variation in Ornamental Rhododendron simsii Planchon.

Rhododendron simsii Planchon is an important ornamental species in the northern hemisphere. Flower color is an important objective of Rhododendron breeding programs. However, information on anthocyanin synthesis in R. simsii is limited. In this research, the regulatory mechanism of anthocyanin biosynthesis in R. simsii was performed through the integrated analysis of metabolome and RNA-seq. A total of 805 and 513 metabolites were screened by positive and negative ionization modes, respectively, In total, 79 flavonoids contained seven anthocyanidins, 42 flavanones, 10 flavans, 13 flavones, and seven flavonols. Methylated and glycosylated derivatives took up the most. Differentially accumulated metabolites were mainly involved in "flavone and flavonol biosynthesis", "cyanoamino acid metabolism", "pyrimidine metabolism", and "phenylalanine metabolism" pathways. For flavonoid biosynthesis, different expression of shikimate O-hydroxycinnamoyltransferase, caffeoyl-CoA O-methyltransferase, flavonoid 3'-monooxygenase, flavonol synthase, dihydroflavonol 4-reductase/flavanone 4-reductase, F3'5'H, chalcone synthase, leucoanthocyanidin reductase, and 5-O-(4-coumaroyl)-D-quinate 3'-monooxygenase genes ultimately led to different accumulations of quercetin, myricetin, cyanidin, and eriodictyol. In flavone and flavonol biosynthesis pathway, differential expression of F3'5'H, flavonoid 3'-monooxygenase and flavonol-3-O-glucoside/galactoside glucosyltransferase genes led to the differential accumulation of quercetin, isovitexin, and laricitrin. This research will provide a biochemical basis for further modification of flower color and genetic breeding in R. simsii and related Rhododendron species.

The transcription factor LBD10 sustains pollen tube growth and integrity by modulating reactive oxygen species homeostasis via the regulation of flavonol biosynthesis in Arabidopsis.

Reproduction in angiosperms relies on the precise growth of pollen tubes, facilitating the delivery of sperm cells to the ovule for double fertilization. LATERAL ORGAN BOUNDARIES DOMAIN10 (LBD10), a plant-specific transcription factor, plays a pivotal role in Arabidopsis pollen development. Here, we uncovered LBD10's function in sustaining pollen tube growth and integrity. The lbd10 mutant exhibited elevated levels of reactive oxygen species (ROS) and hydrogen peroxide (H2O2) in both pollen grains and tubes, leading to compromised pollen tube growth. The inhibition of ROS synthesis and scavenging of excess ROS with an antioxidant treatment each alleviated these defects in lbd10. The lbd10 mutant displayed reduced flavonol accumulation in both pollen grains and tubes. All the altered phenotypes of lbd10 were complemented by expressing LBD10 under its native promoter. Exogenous application of flavonoids recused the defects in pollen tube growth and integrity in lbd10, along with reducing the excess levels of ROS and H2O2. LBD10 directly binds the promoters of key flavonol biosynthesis genes in chromatin and promotes reporter gene expression in Arabidopsis mesophyll protoplasts. Our findings indicate that LBD10 modulates ROS homeostasis by transcriptionally activating genes crucial for flavonol biosynthesis, thereby maintaining pollen tube growth and integrity.