Search Results (71)

Flavonoids serve as crucial plant antioxidants in drought tolerance, yet their antioxidant regulatory mechanisms within mycorrhizal plants remain unclear. In this study, using a two-factor design, trifoliate orange (Poncirus trifoliata (L.) Raf.) seedlings in the four-to-five-leaf stage were either inoculated with Funneliformis mosseae or not, and subjected to well-watered (70–75% of field maximum water-holding capacity) or drought stress (50–55% field maximum water-holding capacity) conditions for 10 weeks. Plant growth performance, photosynthetic physiology, leaf flavonoid content and their antioxidant capacity, reactive oxygen species levels, and activities and gene expression of key flavonoid biosynthesis enzymes were analyzed. Although drought stress significantly reduced root colonization and soil hyphal length, inoculation with F. mosseae consistently enhanced the biomass of leaves, stems, and roots, as well as root surface area and diameter, irrespective of soil moisture. Despite drought suppressing photosynthesis in mycorrhizal plants, F. mosseae substantially improved photosynthetic capacity (measured via gas exchange) and optimized photochemical efficiency (assessed by chlorophyll fluorescence) while reducing non-photochemical quenching (heat dissipation). Inoculation with F. mosseae elevated the total flavonoid content in leaves by 46.67% (well-watered) and 14.04% (drought), accompanied by significantly enhanced activities of key synthases such as phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), 4-coumarate:coA ligase (4CL), and cinnamate 4-hydroxylase (C4H), with increases ranging from 16.90 to 117.42% under drought. Quantitative real-time PCR revealed that both mycorrhization and drought upregulated the expression of PtPAL1, PtCHI, and Pt4CL genes, with soil moisture critically modulating mycorrhizal regulatory effects. In vitro assays showed that flavonoid extracts scavenged radicals at rates of 30.07–41.60% in hydroxyl radical (•OH), 71.89–78.06% in superoxide radical anion (O₂^•−), and 49.97–74.75% in 2,2-diphenyl-1-picrylhydrazyl (DPPH). Mycorrhizal symbiosis enhanced the antioxidant capacity of flavonoids, resulting in higher scavenging rates of •OH (19.07%), O₂^•− (5.00%), and DPPH (31.81%) under drought. Inoculated plants displayed reduced hydrogen peroxide (19.77%), O₂^•− (23.90%), and malondialdehyde (17.36%) levels. This study concludes that mycorrhizae promote the level of total flavonoids in trifoliate orange by accelerating the flavonoid biosynthesis pathway, hence reducing oxidative damage under drought. Full article

To explore the effects of various zinc (Zn) fertilizer application methods and concentrations on foxtail millet quality and flavonoid biosynthesis, we used Zhangzagu 13 as the experimental material. The transcriptome and metabolome were used to examine variations in flavonoid biosynthesis and metabolism in foxtail millet under different Zn application methods. The results showed that different Zn application methods significantly increased the total polyphenol, carotenoid, total flavonoid, and Zn contents in the grains of foxtail millet. Under the basal soil application (S3) and foliar spray (F2) treatments, the total flavonoid content significantly increased by 45.87% and 64.40%, respectively, compared with that of CK. Basal soil Zn fertilization increased the flavonoid content of foxtail millet by up-regulating genes related to flavonoid metabolism and biosynthesis, including flavanone-3-hydroxylase, chalcone isomerase, and leucoanthocyanidin reductase. Foliar Zn application enhanced flavonoid content by up-regulating genes involved in flavonoid metabolic and biosynthetic processes and chalcone isomerase. In conclusion, using Zn fertilizer can improve the synthesis and metabolism of foxtail millet flavonoids, effectively increase the content of functional substances in grains, and realize the biofortification of foxtail millet grains. Full article

The occurrence of anthocyanins in rice (Oryza sativa) and barley (Hordeum vulgare) varies among cultivars, with pigmented varieties (e.g., black rice and purple barley) accumulating higher concentrations due to genetic and environmental factors. The biosynthesis of anthocyanins is regulated by a complex network of structural and regulatory genes. Key enzymes in the pathway include chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and UDP-glucose flavonoid 3-O-glucosyltransferase (UFGT). These genes are tightly controlled by transcription factors (TFs) from the MYB, bHLH (basic helix–loop–helix), and WD40 repeat families, which form the MBW (MYB-bHLH-WD40) regulatory complex. In rice, OsMYB transcription factors such as OsMYB3, OsC1, and OsPL (Purple Leaf) interact with OsbHLH partners (e.g., OsB1, OsB2) to activate anthocyanin biosynthesis. Similarly, in barley, HvMYB genes (e.g., HvMYB10) coordinate with HvbHLH TFs to regulate pigment accumulation. Environmental cues, such as light, temperature, and nutrient availability, further modulate these TFs, influencing the production of anthocyanin. Understanding the genetic and molecular mechanisms behind the biosynthesis of anthocyanins in rice and barley provides opportunities for the development of biofortification strategies that enhance their nutritional value. Full article

Flavonoid synthases (FNSs) are key enzymes catalyzing the conversion of flavanones to flavonoids, yet their functions in citrus remain functionally uncharacterized. In this study, we identified three FNSII genes in the citrus genome. Phylogenetic analysis revealed that citrus FNSII genes share the closest evolutionary distance with apple FNSII genes. Chromosomal localization demonstrated that the three FNSII genes are distributed across two out of nine chromosomes. Gene structure analysis indicated that the majority of motifs within these three FNSII genes are highly conserved. We cloned a gene called CitFNSII-1 from citrus. Transient overexpression of CitFNSII-1 in citrus leaves significantly increased flavonoid content, while simultaneous virus-induced silencing of CitFNSII-1 led to synchronously and significantly reduced gene expression levels and flavonoid content in citrus seedlings. Through the Agrobacterium rhizogenes-mediated genetic transformation system, overexpression of CitFNSII-1 was found to markedly enhance flavonoid accumulation in hairy roots, whereas knockout of CitFNSII-1 resulted in a significant decrease in flavonoid content in hairy roots. Further experiments verified an interaction between CitFNSII-1 and the Chalcone isomerase-1 (CHI-1) protein. The results demonstrated that the flavonoid accumulation patterns of CHI-1 and CitFNSII-1 are highly similar. In conclusion, this study advances the understanding of the flavonoid biosynthesis pathway in citrus and provides a theoretical foundation for molecular breeding strategies in citrus. Full article

Poplar (Populus spp.) is an economically and ecologically important temperate tree species known for its rapid growth. Clonal propagation has facilitated genetic advancements, but it remains challenging due to substantial variations in rooting capacity among poplar species and clones. Poplar clones were divided into two groups based on their rooting ability (high or low), and their transcriptome was analyzed for 3 weeks following stem-cutting propagation to investigate the rooting mechanisms of a hybrid of two fast-growing poplar species (Populus alba × P. tomentiglandulosa). The root length and area of the high-rooting group were 668.7% and 198.4% greater than those of the low-rooting ability group, respectively (maximum p < 0.001). Compared to week 0, genes involved in auxin signaling, cell wall organization, and secondary metabolite biosynthesis were consistently upregulated at 1, 2, and 3 weeks after planting, respectively. The expression of genes associated with cell wall differentiation and flavonoid biosynthesis was greater in the high- than in the low-rooting group at week 2. MYB and AP2/ERF transcription factors, which regulate flavonoid biosynthesis, as well as chalcone isomerase, a key enzyme in early flavonoid biosynthesis and root formation, were upregulated in the high-rooting group. The flavonoid biosynthesis pathway is important in rooting after stem cutting of Populus alba × P. tomentiglandulosa hybrids. Full article

The color of the walnut seed coat is a critical determinant of its market value; however, research into the mechanisms responsible for seed coat color formation is yet to be determined. Using two walnut clones with contrasting pale-yellow and light purple seed coats, we characterized pigmentation, particularly anthocyanin content, using spectrophotometry. We then conducted integrated transcriptomic and metabolomic analyses to identify the molecular mechanisms and pathways underlying their formation. The anthocyanin content in the light purple seed coat clone was significantly greater than that in the clone with a white seed coat. The results of comparative metabolomics indicated that four anthocyanins (delphinidin, cyanidin-3-(caffeoylglucoside), pelargonidin-3-(6″-caffeoylglucoside), and delphinidin-3-O-sophoroside) were significantly more abundant in the light purple seed coat clone. These anthocyanins were the key pigments responsible for the light purple coloration of the walnut seed coat. Furthermore, comparative transcriptomics revealed that structural genes in the anthocyanin biosynthesis pathway (e.g., phenylalanine ammonia-lyase, 4-coumarate-CoA ligase, chalcone isomerase, and bronze-1) were significantly upregulated in the purple seed coat clone. Coexpression network analysis revealed that several transcription factors (e.g., ARF, bHLH, and MYB-related) were significantly correlated with the upregulation of these structural genes and the accumulation of four key anthocyanins. These transcription factors may serve as critical regulators influencing seed coat color formation. In conclusion, these findings establish a strong theoretical foundation for walnut breeding aimed at developing diverse seed coat colors. Full article

The seed-coat color and seed size have an impact on both the evolutionary fitness and the grain yield of crops. Soybean is a major oil crop, and the seed-coat color and seed size exhibit natural diversity among the different soybean varieties. Here, we found an R2R3-MYB transcription factor of GmMYB62, which shows a significant increase in expression as the seed-coat color changes from yellow to black in different soybean varieties. The GmMYB62 was specifically highly expressed in reproductive organs, especially in floral organs in soybeans. The GmMYB62 encodes a nuclear protein that contains two MYB domains. In the phylogenetic analysis, the GmMYB62 was relatively conserved after the divergence of the monocots and dicots, and it also grouped with transcriptional repressors of MYBs in anthocyanin synthesis. The GmMYB62 was overexpressed in Arabidopsis and the seeds displayed a pale-brown coat in GmMYB62 overexpression lines, in contrast to the dark-brown seed coat observed in wild-type of Col-0. The anthocyanin content in the GmMYB62 overexpression lines was dramatically reduced when compared to Col-0. Additionally, the seeds in overexpression lines showed shorter lengths, larger widths, and lower thousand-seed weights than those in Col-0. Furthermore, the genes related to anthocyanin synthesis and seed size regulation were investigated, and expression of eight genes that involved in anthocyanin synthesis pathway, like chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), and anthocyanidin synthase (ANS) were severely inhibited in the GmMYB62 overexpression lines when compared to Col-0. In addition, the ARGOS-LIKE (ARL), B-Type Cyclin 1 (CYCB1), and enhancer of DA1-1 (EOD3), which govern cell expansion and proliferation, were highly expressed in GmMYB62 overexpression lines when compared to Col-0. Overall, this study sheds new light on the control of seed-coat color and seed size by GmMYB62 and provides potentially valuable targets for improving crop seed quality. Full article

Melatonin (MT) is an elicitor that stimulates phenolic compounds biosynthesis and accumulation in fruits and vegetables. However, its role in regulating phenolic compounds and the phenylpropane metabolism during pepper ripening is unclear. To investigate how exogenous MT regulates phenolic compounds biosynthesis during pepper ripening, pepper plant surfaces were sprayed with different MT concentrations (0 and 100 µmol·L⁻¹) 10 days after anthesis. MT treatment improved pepper fruits quality. In particular, total phenolics and flavonoids compounds levels were elevated, indicating that MT affected phenolic compounds metabolism. Furthermore, metabolomics identified 15 substances exhibiting high fold-change values after MT treatment, including chlorogenic acid, gallic acid, ferulic acid, caffeic acid, cynarin, p-coumaric acid, cinnamic acid, gentianic acid, benzoic acid, sinapic acid, p-hydroxybenzoic acid, protocatechuic acid, rutin, quercetin, and kaempferol. Shikimate dehydrogenase, phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate-Coa ligase, chalcone synthase, and chalcone isomerase activities were also evaluated. MT upregulated the expression of genes involved in phenolic compounds synthesis during pepper ripening and that of corresponding genes involved in the endogenous MT anabolic pathway, promoting endogenous. The polyphenolics and carbohydrates are indicators of the botanical and geographical origin of Serbian autochthonous clones of red spice MT synthesis throughout pepper ripening. In summary, exogenous MT accelerates phenolic compounds synthesis in pepper fruits by activating phenylpropane metabolism and modulating endogenous hormone signaling networks. This is expected to offer a revolutionary strategy to reinforce pepper plants resistance and quality. Full article

Chalcone isomerase (CHI) is not only an enzyme related to flavonoid biosynthesis, but also one of the key enzymes in the flavonoid metabolic pathway. In this study, members of the CHI gene family were identified in the whole genome of sweet potato. Bioinformatics methods were used to analyze the physical and chemical properties, systematic evolution, conserved domain, chromosome location, cis-acting elements of the promoter, and so on, of CHI gene family members. In addition, the tissue site-specific expression of CHI gene family members and their expression patterns under three kinds of abiotic stress were analyzed. The results showed that five members of IbCHI gene family were identified in sweet potato, which were unevenly distributed on four chromosomes. The protein secondary structure and tertiary structure were consistent, and there was a conservative domain related to chalcone isomerase. The prediction of subcellular localization showed that it was mainly located in cytoplasm and chloroplast. Systematic evolution showed that the members of sweet potato CHI gene family could be divided into Type I-IV, and the Type I gene IbCHI1 showed CHI catalytic activity in transgenic callus. The collinearity gene pairs were identified between sweet potato and allied species. Its promoter contains light response elements, hormone response elements, and stress response elements. The results of real-time fluorescence quantitative PCR (qRT-PCR) analysis showed that the expression of the IbCHI gene was tissue-specific and that the catalytic genes IbCHI1 and IbCHI5 serve as primary responders to abiotic stress, while the non-catalytic members IbCHI3 and IbCHI4 may fine-tune metabolic flux or participate in low-temperature, salt, and drought stress signaling. This study can provide a theoretical basis for a follow-up functional genomics study of the chalcone isomerase gene family in sweet potato. Full article

Waxy maize (Zea mays L. sinensis kulesh) contains a lot of nutrients, and has a long history of cultivation and extensive consumption. In this study, six waxy maize varieties of white (J18 and W2000), yellow (J41 and J7), and black (J10 and J20) were selected as experimental materials, and the functional nutrients and the differences in anthocyanin anabolic pathways in maize kernels at 14, 18, 22, and 26 days after pollination were determined. The result show that the varieties and kernel development stages had significant effect on the carotenoid, soluble sugar, vitamin C, anthocyanin, and mineral element content. The black waxy maize varieties had a higher anthocyanin content, which plays an important role in maize kernel coloration, whereas the yellow and black waxy maize varieties exhibit a greater abundance of mineral elements. Furthermore, the phenylalanine content, as well as the activities of phenylalanine ammonia lyase (PAL), chalcone isomerase (CHI), dihydroflavonol reductase (DFR), and flavonoid 3-glucosyltransferase (UFGT), played a significant role in the anthocyanin biosynthetic pathway. In conclusion, the comprehensive functional quality of waxy maize decreased with the delay of kernel development stage, and the black waxy maize varieties demonstrated superior functional quality. The PAL and CHI played a primary role in the initial phase of anthocyanin accumulation, while UFGT gradually assumed control in the subsequent stages. Full article

White clover (Trifolium repens) is vulnerable to drought stress. In response to abiotic stress, plants are regulated by NAC transcription factors. The NAC in white clover has not been thoroughly documented until recently. We have identified one white clover NAC transcription factor called TrNAC002. TrNAC002’s coding sequence is localized to specific regions on the 3P and 5O chromosomes of white clover and is part of a single-copy nuclear gene. Subcellular localization demonstrates that TrNAC002 is located in the nucleus, while the transcriptional activity assay indicates its transcriptional activity. Arabidopsis plants overexpressing TrNAC002 (OE) exhibit enlarged leaves and increased lateral root growth compared to the wild type (WT). Additionally, the expression levels of the shoot apical meristem (SAM), WUSCHEL (WUS), DNA-binding protein (DBP), and auxin-induced in root cultures3 (AIR3) genes are significantly higher in OE as compared to WT. These findings imply that TrNAC002 could promote vegetative growth by increasing the expression of these genes. Under natural drought stress, OE can survive in dry soil for a longer period of time than WT. Furthermore, OE exhibits a lower level of reactive oxygen species (ROS) level and a higher content of flavonoids than WT. This is also positively correlated with an increased flavonoid content. In white clover, the expression of TrNAC002, chalcone synthase (CHS), and chalcone isomerase (CHI) in leaves demonstrates significant upregulation after drought stress and ABA treatment, as does the flavonoid content. However, the pTRV-VIGS experiment suggests that pTRV2-TrNAC002 white clover shrinks compared to the Mock and Water controls. Additionally, pTRV2-TrNAC002 white clover displays a statistically higher malondialdehyde (MDA) content than the Mock and Water controls, and a significantly lower level of total antioxidant activities, flavonoid content, CHS and CHI relative expression than that of the Mock and Water controls. These findings indicate that TrNAC002 responds to drought and modulates flavonoid biosynthesis in white clover. This study is the first to suggest that TrNAC002 likely responds to drought via ABA and enhances plant drought resistance by synthesizing flavonoids. Full article

Elevated levels of reactive oxygen species (ROS) are caused by ultraviolet B radiation (UV-B) stress. In response, plants strengthen their cell membranes, impeding photosynthesis. Additionally, UV-B stress initiates oxidative stress within the antioxidant defense system and alters secondary metabolism, particularly by increasing the quantity of UV-absorbing compounds such as flavonoids. The v-myb avian myeloblastosis viral oncogene homolog (MYB) transcription factor (TF) may participate in a plant’s response to UV-B damage through its regulation of flavonoid biosynthesis. In this study, we discovered that the photosynthetic activity of Rhododendron chrysanthum Pall. (R. chrysanthum) decreased when assessing parameters of chlorophyll (PSII) fluorescence parameters under UV-B stress. Concurrently, antioxidant system enzyme expression increased under UV-B exposure. A multi-omics data analysis revealed that acetylation at the K68 site of the RcTRP5 (telomeric repeat binding protein of Rhododendron chrysanthum Pall.) transcription factor was upregulated. This acetylation modification of RcTRP5 activates the antioxidant enzyme system, leading to elevated expression levels of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Upregulation is also observed at the K95 site of the chalcone isomerase (CHI) enzyme and the K178 site of the anthocyanidin synthase (ANS) enzyme. We hypothesize that RcTRP5 influences acetylation modifications of CHI and ANS in flavonoid biosynthesis, thereby indirectly regulating flavonoid production. This study demonstrates that R. chrysanthum can be protected from UV-B stress by accumulating flavonoids. This could serve as a useful strategy for enhancing the plant’s flavonoid content and provide a valuable reference for research on the metabolic regulation mechanisms of other secondary substances. Full article

Buckwheat possesses significant nutritional content and contains different bioactive compounds, such as total flavonoids, which enhance its appeal to consumers. This study employed single-factor experiments and the response surface methodology to identify the optimal germination conditions for enhancing the total flavonoid content in buckwheat sprouts through ultraviolet-B treatment. The research showed that buckwheat sprouts germinated for 3 days at a temperature of 28.7 °C while being exposed to ultraviolet-B radiation at an intensity of 30.0 μmol·m⁻²·s⁻¹ for 7.6 h per day during the germination period resulted in the highest total flavonoid content of 1872.84 μg/g fresh weight. Under these specified conditions, ultraviolet-B treatment significantly elevated the activity and gene expression levels of enzymes related to the phenylpropanoid metabolic pathway, including phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4-coumarate coenzyme A ligase, and chalcone isomerase. Ultraviolet-B treatment caused oxidative damage to buckwheat sprouts and inhibited their growth, but ultraviolet-B treatment also enhanced the activity of key enzymes in the antioxidant system, such as catalase, peroxidase, superoxide dismutase, and ascorbate peroxidase. This research provided a technical reference and theoretical support for enhancing the isoflavone content in buckwheat sprouts through ultraviolet-B treatment. Full article

Soil salinization is a significant environmental stress factor, threatening global agricultural yield and ecological security. Plants must effectively cope with the adverse effects of salt stress on survival and successful reproduction. Lateral Organ Boundaries (LOB) Domain (LBD) genes, a gene family encoding plant-specific transcription factors (TFs), play important roles in plant growth and development. Here, we identified and functionally characterized the LBD family TF PtrLBD41 from Populus trichocarpa, which can be induced by various abiotic stresses, including salt, dehydration, low temperature, and Abscisic Acid (ABA). Meanwhile, transgenic plants overexpressing PtrLBD41 showed a better phenotype and higher tolerance than the wild-type (WT) plants under salt stress treatment. Transcriptome analysis found that the differentially expressed genes (DEGs) between the WT and overexpression (OE) line were enriched in the flavonoid biosynthetic process, in which chalcone synthases (CHS), naringenin 3-dioxygenase (F3H), and chalcone isomerase (CHI) were significantly up-regulated under salt stress conditions through qRT-PCR analysis. Therefore, we demonstrate that PtrLBD41 plays an important role in the tolerance to salt stress in P. trichocarpa. Full article

Camellia hainanica is one of the camellia plants distributed in tropical regions, and its regeneration system and genetic transformation are affected by callus browning. However, the underlying mechanism of Camellia hainanica callus browning formation remains largely unknown. To investigate the metabolic basis and molecular mechanism of the callus browning of Camellia hainanica, histological staining, high-throughput metabolomics, and transcriptomic assays were performed on calli with different browning degrees (T1, T2, and T3). The results of histological staining revealed that the brown callus cells had obvious lignification and accumulation of polyphenols. Widely targeted metabolomics revealed 1190 differentially accumulated metabolites (DAMs), with 53 DAMs annotated as phenylpropanoids and flavonoids. Comparative transcriptomics revealed differentially expressed genes (DEGs) of the T2 vs. T1 associated with the biosynthesis and regulation of flavonoids and transcription factors in Camellia hainanica. Among them, forty-four enzyme genes associated with flavonoid biosynthesis were identified, including phenylalaninase (PAL), 4-coumaroyl CoA ligase (4CL), naringenin via flavanone 3-hydroxylase (F3H), flavonol synthase (FLS), Chalcone synthase (CHS), Chalcone isomerase (CHI), hydroxycinnamoyl-CoA shikimate transferase (HCT), Dihydroflavonol reductase (DFR), anthocyanin reductase (LAR), anthocyanin synthetase (ANS), and anthocyanin reductase (ANR). Related transcription factors R2R3-MYB, basic helix-loop-helix (bHLH), and WRKY genes also presented different expression patterns in T2 vs. T1. These results indicate that the browning of calli in Camellia hainanica is regulated at both the transcriptional and metabolic levels. The oxidation of flavonoids and the regulation of related structural genes and transcription factors are crucial decisive factors. This study preliminarily revealed the molecular mechanism of the browning of the callus of Camellia hainanensis, and the results can provide a reference for the anti-browning culture of Camellia hainanica callus. Full article