Structure and function of enzymes involved in the biosynthesis of phenylpropanoids

Metabolomic and transcriptomic analysis of flavonoids biosynthesis mechanisms in mulberry fruit (Hongguo 2) under exogenous hormone treatments

The mulberry fruit is prized for its superior nutrition value and abundant color due to its high flavone content. To enhance comprehension of flavone biogenesis induced by external hormones, we sprayed exogenous ethylene (ETH), indoleacetic acid (IAA) and spermine (SPM) on mulberry fruit (Hongguo 2) during its color-changed period. The levels of anthocyanin, titratable acid, soluble sugar and endogenous hormones were determined after hormone treatment, integrated transcriptome and metabolome analysis were performed for mechanism exploration. Our results indicated that exogenous ETH, SPM, and IAA play important roles in mulberry ripening, including acid reduction, sugar increase and flavonoid synthesis.

Chemical and physical changes induced by cold plasma treatment of foods: A critical review

Cold plasma treatment is an innovative technology in the food processing and preservation sectors. It is primarily employed to deactivate microorganisms and enzymes without heat and chemical additives; hence, it is often termed a "clean and green" technology. However, food quality and safety challenges may arise during cold plasma processing due to potential chemical interactions between the plasma reactive species and food components. This review aims to consolidate and discuss data on the impact of cold plasma on the chemical constituents and physical and functional properties of major food products, including dairy, meat, nuts, fruits, vegetables, and grains. We emphasize how cold plasma induces chemical modification of key food components, such as water, proteins, lipids, carbohydrates, vitamins, polyphenols, and volatile organic compounds. Additionally, we discuss changes in color, pH, and organoleptic properties induced by cold plasma treatment and their correlation with chemical modification. Current studies demonstrate that reactive oxygen and nitrogen species in cold plasma oxidize proteins, lipids, and bioactive compounds upon direct contact with the food matrix. Reductions in nutrients and bioactive compounds, including polyunsaturated fatty acids, sugars, polyphenols, and vitamins, have been observed in dairy products, vegetables, fruits, and beverages following cold plasma treatment. Furthermore, structural alterations and the generation of volatile and non-volatile oxidation products were observed, impacting the color, flavor, and texture of food products. However, the effects on dry foods, such as seeds and nuts, are comparatively less pronounced. Overall, this review highlights the drawbacks, challenges, and opportunities associated with cold plasma treatment in food processing.

Methyl jasmonate-loaded composite biofilm sustainably alleviates chilling lignification of loquat fruit during postharvest storage

In this work, the MeJA-loaded gelatin/pullulan/chitosan composite biofilm was prepared to inhibit the chilling lignification of the loquat fruit during storage at 0 °C. The firmness and lignin content were decreased by 89 % and 81.77 % after MeJA-loaded biofilm treatment. Malondialdehyde (MDA) production was almost completely suppressed and chilling injury of loquat fruit was significantly reduced. Enzyme activity results show that the biofilm alleviated chilling lignification mainly by inhibiting peroxidase (POD) activity in the phenylpropanoid pathway (PCCs = 0.715, with lignin content). Also, the conventional MeJA vapor treatment only alleviated lignification on day 3, but the biofilm treatment had a better and more sustained effect throughout the whole storage due to its sustained release ability. Besides, the biofilm had good mechanical properties, transparency and water vapor transmission rate. This work indicates that loading preservatives into biofilms has a promising application prospect for inhibiting the postharvest quality deterioration of fruit and vegetables.

Glutamine induces lateral root initiation, stress responses, and disease resistance in Arabidopsis

The production of glutamine (Gln) from NO3- and NH4+ requires ATP, reducing power, and carbon skeletons. Plants may redirect these resources to other physiological processes using Gln directly. However, feeding Gln as the sole nitrogen (N) source has complex effects on plants. Under optimal concentrations, Arabidopsis (Arabidopsis thaliana) seedlings grown on Gln have similar primary root lengths, more lateral roots, smaller leaves, and higher amounts of amino acids and proteins compared to those grown on NH4NO3. While high levels of Gln accumulate in Arabidopsis seedlings grown on Gln, the expression of GLUTAMINE SYNTHETASE1;1 (GLN1;1), GLN1;2, and GLN1;3 encoding cytosolic GS1 increases and expression of GLN2 encoding chloroplastic GS2 decreases. These results suggest that Gln has distinct effects on regulating GLN1 and GLN2 gene expression. Notably, Arabidopsis seedlings grown on Gln have an unexpected gene expression profile. Compared with NH4NO3, which activates growth-promoting genes, Gln preferentially induces stress- and defense-responsive genes. Consistent with the gene expression data, exogenous treatment with Gln enhances disease resistance in Arabidopsis. The induction of Gln-responsive genes, including PATHOGENESIS-RELATED1, SYSTEMIC ACQUIRED RESISTANCE DEFICIENT1, WRKY54, and WALL ASSOCIATED KINASE1, is compromised in salicylic acid (SA) biosynthetic and signaling mutants under Gln treatments. Together, these results suggest that Gln may partly interact with the SA pathway to trigger plant immunity.

Phytoestrogens: Chemistry, potential health benefits, and their medicinal importance

Phytoestrogens, also known as xenoestrogens, are secondary metabolites derived from plants that have similar structures and biological effects as human estrogens. These compounds do not directly affect biological functions but can act as agonists or antagonists depending on the level of endogenous estrogen in the body. Phytoestrogens may have an epigenetic mechanism of action independent of estrogen receptors. These compounds are found in more than 300 plant species and are synthesized through the phenylpropanoid pathway, with specific enzymes leading to various chemical structures. Phytoestrogens, primarily phenolic compounds, include isoflavonoids, flavonoids, stilbenes, and lignans. Extensive research in animals and humans has demonstrated the protective effects of phytoestrogens on estrogen-dependent diseases. Clinical trials have also shown their potential benefits in conditions such as osteoporosis, Parkinson's disease, and certain types of cancer. This review provides a concise overview of phytoestrogen classification, chemical diversity, and biosynthesis and discusses the potential therapeutic effects of phytoestrogens, as well as their preclinical and clinical development.

Metabolomic Profiling of Floccularia luteovirens from Different Geographical Regions Proposes a Novel Perspective on Their Antioxidative Activities

Floccularia luteovirens, an endemic resource of the Tibetan Plateau, possesses significant medicinal and ecological values. However, the understanding of antioxidant capacity and metabolic profiling of F. luteovirens from diverse regions remains elusive due to limited resources. Therefore, to comprehensively comprehend the antioxidant capacity and metabolite diversity of F. luteovirens, we conducted a rounded analysis of its antioxidant capacity from three distinct regions using both untargeted and targeted metabolomics. Determination of antioxidant indices, such as ferric ion-reducing antioxidant power (FRAP), total phenolic content (TPC), and flavonoid content (FC), revealed the robust antioxidant capacity of F. luteovirens. QL F. luteovirens (QLFL) exhibited no significant difference compared to ZD F. luteovirens (ZDFL); however, both were significantly distinct from XH F. luteovirens (XHFL) across multiple indices. Furthermore, a positive correlation was observed between FRAP and flavonoid content. A total of 5782 metabolites were identified and chemically classified. Metabolites of F. luteovirens varied significantly at different regions and eight key differential metabolites were screened. Phenylalanine, tyrosine and tryptophan biosynthesis, phenylalanine metabolism, and cyanoamino acid metabolism were the main different regulatory pathways. Consequently, the disparities in the antioxidant activity of F. luteovirens may primarily be ascribed to the biosynthesis and metabolism of phenylalanine, while vanillic acid could potentially serve as a pivotal metabolite influencing the antioxidative capacity of F. luteovirens by targeted metabolomics. These findings enhance our understanding of the composition of F. luteovirens and provide valuable resources for its comprehensive utilization and targeted development.

Integrative analysis of the metabolome and transcriptome provides insights into the mechanisms of lignan biosynthesis in Herpetospermum pedunculosum (Cucurbitaceae)

BACKGROUND

Herpetospermum pedunculosum (Ser.) C. B. Clarke is a traditional Chinese herbal medicine that heavily relies on the lignans found in its dried ripe seeds (Herpetospermum caudigerum), which have antioxidant and hepatoprotective functions. However, little is known regarding the lignan biosynthesis in H. pedunculosum. In this study, we used metabolomic (non-targeted UHPLC-MS/MS) and transcriptome (RNA-Seq) analyses to identify key metabolites and genes (both structural and regulatory) associated with lignan production during the green mature (GM) and yellow mature (YM) stages of H. pedunculosum.

RESULTS

The contents of 26 lignan-related metabolites and the expression of 30 genes involved in the lignan pathway differed considerably between the GM and YM stages; most of them were more highly expressed in YM than in GM. UPLC-Q-TOF/MS confirmed that three Herpetospermum-specific lignans (including herpetrione, herpetotriol, and herpetin) were found in YM, but were not detected in GM. In addition, we proposed a lignan biosynthesis pathway for H. pedunculosum based on the fundamental principles of chemistry and biosynthesis. An integrated study of the transcriptome and metabolome identified several transcription factors, including HpGAF1, HpHSFB3, and HpWOX1, that were highly correlated with the metabolism of lignan compounds during seed ripening. Furthermore, functional validation assays revealed that the enzyme 4-Coumarate: CoA ligase (4CL) catalyzes the synthesis of hydroxycinnamate CoA esters.

CONCLUSION

These results will deepen our understanding of seed lignan biosynthesis and establish a theoretical basis for molecular breeding of H. pedunculosum.

Fulvic Acid Promotes Legume-Rhizobium Symbiosis by Stimulating Endogenous Flavonoids Synthesis and Secretion

Fulvic acid (FA) promotes symbiosis between legumes and rhizobia. To elucidate from the aspect of symbiosis, the effects of root irrigation of water-soluble humic materials (WSHM) or foliar spraying of its highly active component, FA, on soybean root exudates and on rhizosphere microorganisms were investigated. As a result, WSHM/FA treatments significantly altered root exudate metabolite composition, and isoflavonoids were identified as key contributors in both treatments compared to the control. Increased expression of genes related to the isoflavonoid biosynthesis were validated by RT-qPCR in both treatments, which notably elevated the synthesis of symbiotic signals genistein, daidzin, coumestrol, and biochanin A. Moreover, the WSHM/FA treatments induced a change in rhizosphere microbial community, coupled with an increase in the relative abundance of rhizobia. Our findings showed that WSHM/FA promotes symbiosis by stimulating the endogenous flavonoid synthesis and leads to rhizobia accumulation in the rhizosphere. This study provides new insights into mechanisms underlying the FA-mediated promotion of symbiosis.

Bacillus cereus G2 alleviate salt stress in Glycyrrhiza uralensis Fisch. by balancing the downstream branches of phenylpropanoids and activating flavonoid biosynthesis

The salinity environment is one of the biggest threats to Glycyrrhiza uralensis Fisch. (G. uralensis) growth, resulting from the oxidative stress caused by excess reactive oxygen species (ROS). Flavonoids are the main pharmacodynamic composition and help maintain ROS homeostasis and mitigate oxidative damage in G. uralensis in the salinity environment. To investigate whether endophytic Bacillus cereus G2 can improve the salt-tolerance of G. uralensis through controlling flavonoid biosynthesis, the transcriptomic and physiological analysis of G. uralensis treated by G2 in the saline environment was conducted, focused on flavonoid biosynthesis-related pathways. Results uncovered that salinity inhibited flavonoids synthesis by decreasing the activities of phenylalanine ammonialyase (PAL) and 4-coumarate-CoA ligase (4CL) (42% and 39%, respectively) due to down-regulated gene Glyur000910s00020578 at substrate level, and then decreasing the activities of chalcone isomerase (CHI) and chalcone synthase (CHS) activities (50% and 42%, respectively) due to down-regulated genes Glyur006062s00044203 and Glyur000051s00003431, further decreasing isoliquiritigenin content by 53%. However, salt stress increased liquiritin content by 43%, which might be a protective mechanism of salt-treated G. uralensis seedlings. Interestingly, G2 enhanced PAL activity by 27% whereas reduced trans-cinnamate 4-monooxygenase (C4H) activity by 43% which could inhibit lignin biosynthesis but promote flavonoid biosynthesis of salt-treated G. uralensis at the substrate level. G2 decreased shikimate O-hydroxycinnamoyltransferase (HCT) activity by 35%, increased CHS activity by 54% through up-regulating the gene Glyur000051s00003431 encoding CHS, and increased CHI activity by 72%, thereby decreasing lignin (34%) and liquiritin (24%) content, but increasing isoliquiritigenin content (35%), which could mitigate oxidative damage and changed salt-tolerance mechanism of G. uralensis.

Reconstructing curcumin biosynthesis in yeast reveals the implication of caffeoyl-shikimate esterase in phenylpropanoid metabolic flux

Curcumin is a polyphenolic natural product from the roots of turmeric (Curcuma longa). It has been a popular coloring and flavoring agent in food industries with known health benefits. The conventional phenylpropanoid pathway is known to proceed from phenylalanine via p-coumaroyl-CoA intermediate. Although hydroxycinnamoyl-CoA: shikimate hydroxycinnamoyl transferase (HCT) plays a key catalysis in the biosynthesis of phenylpropanoid products at the downstream of p-coumaric acid, a recent discovery of caffeoyl-shikimate esterase (CSE) showed that an alternative pathway exists. Here, the biosynthetic efficiency of the conventional and the alternative pathway in producing feruloyl-CoA was examined using curcumin production in yeast. A novel modular multiplex genome-edit (MMG)-CRISPR platform was developed to facilitate rapid integrations of up to eight genes into the yeast genome in two steps. Using this MMG-CRISPR platform and metabolic engineering strategies, the alternative CSE phenylpropanoid pathway consistently showed higher titers (2-19 folds) of curcumin production than the conventional pathway in engineered yeast strains. In shake flask cultures using a synthetic minimal medium without phenylalanine, the curcumin production titer reached up to 1.5 mg/L, which is three orders of magnitude (∼4800-fold) improvement over non-engineered base strain. This is the first demonstration of de novo curcumin biosynthesis in yeast. Our work shows the critical role of CSE in improving the metabolic flux in yeast towards the phenylpropanoid biosynthetic pathway. In addition, we showcased the convenience and reliability of modular multiplex CRISPR/Cas9 genome editing in constructing complex synthetic pathways in yeast.

Bacillus velezensis WB induces systemic resistance in watermelon against Fusarium wilt

BACKGROUND

Our previous findings indicated that Bacillus velezensis WB could control Fusarium wilt by changing the structure of the microbial community in the watermelon rhizosphere. However, there are few studies on its mechanism in the pathogen resistance of watermelon. Therefore, in this study, we determined the mechanism of B. velezensis WB-induced systemic resistance in watermelon against Fusarium wilt through glasshouse pot experiments.

RESULTS

The results showed that B. velezensis WB significantly reduced the incidence and disease index of Fusarium wilt in watermelon. B. velezensis WB can enhance the basal immunity of watermelon plants by: increasing the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD), superoxide dismutase (SOD) and β-1,3-glucanase; accumulating lignin, salicylic acid (SA) and jasmonic acid (JA); reducing malondialdehyde (MDA) concentrations; and inducing callus deposition in watermelon plant cells. RNA-seq analysis showed that 846 watermelon genes were upregulated and 612 watermelon genes were downregulated in the WF treatment. This process led to the activation of watermelon genes associated with auxin, gibberellin, SA, ethylene and JA, and the expression of genes in the phenylalanine biosynthetic pathway was upregulated. In addition, transcription factors involved in plant resistance to pathogens, such as MYB, NAC and WRKY, were induced. Gene correlation analysis showed that Cla97C10G195840 and Cla97C02G049930 in the phenylalanine biosynthetic pathway, and Cla97C02G041360 and Cla97C10G197290 in the plant hormone signal transduction pathway showed strong correlations with other genes.

CONCLUSION

Our results indicated that B. velezensis WB is capable of inducing systemic resistance in watermelon against Fusarium wilt. © 2023 Society of Chemical Industry.

Roles of the N-terminal motif in improving the activity and soluble expression of phenylalanine ammonia lyases in Escherichia coli

Phenylalanine ammonia-lyase (PAL) has various applications in fine chemical manufacturing and the pharmaceutical industry. In particular, PAL derived from Anabaena variabilis (AvPAL) is used as a therapeutic agent to the treat phenylketonuria in clinical settings. In this study, we aligned the amino acid sequences of AvPAL and PAL derived from Nostoc punctiforme (NpPAL) to obtain several mutants with enhanced activity, expression yield, and thermal stability via amino acid substitution and saturation mutagenesis at the N-terminal position. Enzyme kinetic experiments revealed that the kcat values of NpPAL-N2K, NpPAL-I3T, and NpPAL-T4L mutants were increased to 3.2-, 2.8-, and 3.3-fold that of the wild-type, respectively. Saturation mutagenesis of the fourth amino acid in AvPAL revealed that the kcat values of AvPAL-L4N, AvPAL-L4P, AvPAL-L4Q and AvPAL-L4S increased to 4.0-, 3.7-, 3.6-, and 3.2-fold, respectively. Additionally, the soluble protein yield of AvPAL-L4K increased to approximately 14 mg/L, which is approximately 3.5-fold that of AvPAL. Molecular dynamics studies further revealed that maintaining the attacking state of the reaction and N-terminal structure increased the rate of catalytic reaction and improved the solubility of proteins. These findings provide new insights for the rational design of PAL in the future.

Integrated Metabolomic and Transcriptomic Profiles Provide Insights into the Mechanisms of Anthocyanin and Carotenoid Biosynthesis in Petals of Medicago sativa ssp. sativa and Medicago sativa ssp. falcata

The petals of Medicago sativa ssp. sativa and M. sativa ssp. falcata are purple and yellow, respectively. Free hybridization between M. sativa ssp. sativa and M. sativa ssp. falcata has created hybrids with various flower colors in nature. Moreover, the flower colors of alfalfa are closely correlated with yield, nutritional quality, stress tolerance and other agronomic characteristics. To elucidate the underlying mechanisms of flower color formation in M. sativa ssp. sativa and M. sativa ssp. falcata, we conducted an integrative analysis of the transcriptome and metabolome of alfalfa with three different petal colors (purple, yellow and cream). The metabolic profiles suggested that anthocyanins and carotenoids are the crucial pigments in purple and yellow flowers, respectively. A quantitative exploration of the anthocyanin and carotenoid components indicated that the accumulations of cyanidin, delphinidin, peonidin, malvidin, pelargonidin and petunidin derivatives are significantly higher in purple flowers than in cream flowers. In addition, the content of carotenes (phytoene, α-carotene and β-carotene) and xanthophylls (α-cryptoxanthin, lutein, β-cryptoxanthin, zeaxanthin, antheraxanthin and violaxanthin derivatives) was markedly higher in yellow flowers than in cream flowers. Furthermore, we found that delphinidin-3,5-O-diglucoside and lutein were the predominant pigments accumulated in purple and yellow flowers, respectively. The transcriptomic results revealed that twenty-five upregulated structural genes (one C4H, three 4CL, twelve CHS, two CHI, one F3H, one F3'H, one F3'5'H and four DFR) are involved in the accumulation of anthocyanins in purple flowers, and nine structural genes (two PSY, one ZDS, two CRTISO, two BCH, one ZEP and one ECH) exert an effect on the carotenoid biosynthesis pathway in yellow flowers. The findings of this study reveal the underlying mechanisms of anthocyanin and carotenoid biosynthesis in alfalfa with three classic flower colors.

Integrated transcriptomic and metabolomic analyses elucidate the mechanism of flavonoid biosynthesis in the regulation of mulberry seed germination under salt stress

Seed propagation is the main method of mulberry expansion in China, an important economic forest species. However, seed germination is the most sensitive stage to various abiotic stresses, especially salinity stress. To reveal the molecular regulatory mechanism of mulberry seed germination under salt stress, flavonoid metabolomics and transcriptomics analyses were performed on mulberry seeds germinated under 50 and 100 mmol/L NaCl stress. Analysis of the flavonoid metabolome revealed that a total of 145 differential flavonoid metabolites (DFMs) were classified into 9 groups, 40 flavonols, 32 flavones, 16 chalcones and 14 flavanones. Among them, 61.4% (89) of the DFMs accumulated continuously with increasing salt concentration, reaching the highest level at a 100 mmol/L salt concentration; these DFMs included quercetin-3-O-glucoside (isoquercitrin), kaempferol (3,5,7,4'-tetrahydroxyflavone), quercetin-7-O-glucoside, taxifolin (dihydroquercetin) and apigenin (4',5,7-trihydroxyflavone), indicating that these flavonoids may be key metabolites involved in the response to salt stress. Transcriptional analysis identified a total of 3055 differentially expressed genes (DEGs), most of which were enriched in flavonoid biosynthesis (ko00941), phenylpropanoid biosynthesis (ko00940) and biosynthesis of secondary metabolites (ko01110). Combined analysis of flavonoid metabolomic and transcriptomic data indicated that phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), chalcone synthase (CHS), flavonol synthase (FLS), bifunctional dihydroflavonol 4-reductase/flavanone 4-reductase (DFR) and anthocyanidin reductase (ANR) were the key genes involved in flavonoid accumulation during mulberry seed germination under 50 and 100 mmol/L NaCl stress. In addition, three transcription factors, MYB, bHLH and NAC, were involved in the regulation of flavonoid accumulation under salt stress. The results of quantitative real-time PCR (qRT‒PCR) validation showed that the expression levels of 11 DEGs, including 7 genes involved in flavonoid biosynthesis, under different salt concentrations were consistent with the transcriptomic data, and parallel reaction monitoring (PRM) results showed that the expression levels of 6 key enzymes (proteins) involved in flavonoid synthesis were consistent with the accumulation of flavonoids. This study provides a new perspective for investigating the regulatory role of flavonoid biosynthesis in the regulation of mulberry seed germination under salt stress at different concentrations.

Genome-Wide Characterization of the Phenylalanine Ammonia-Lyase Gene Family and Their Potential Roles in Response to Aspergillus flavus L. Infection in Cultivated Peanut (Arachis hypogaea L.)

Phenylalanine ammonia-lyase (PAL) is an essential enzyme in the phenylpropanoid pathway, in which numerous aromatic intermediate metabolites play significant roles in plant growth, adaptation, and disease resistance. Cultivated peanuts are highly susceptible to Aspergillus flavus L. infection. Although PAL genes have been characterized in various major crops, no systematic studies have been conducted in cultivated peanuts, especially in response to A. flavus infection. In the present study, a systematic genome-wide analysis was conducted to identify PAL genes in the Arachis hypogaea L. genome. Ten AhPAL genes were distributed unevenly on nine A. hypogaea chromosomes. Based on phylogenetic analysis, the AhPAL proteins were classified into three groups. Structural and conserved motif analysis of PAL genes in A. hypogaea revealed that all peanut PAL genes contained one intron and ten motifs in the conserved domains. Furthermore, synteny analysis indicated that the ten AhPAL genes could be categorized into five pairs and that each AhPAL gene had a homologous gene in the wild-type peanut. Cis-element analysis revealed that the promoter region of the AhPAL gene family was rich in stress- and hormone-related elements. Expression analysis indicated that genes from Group I (AhPAL1 and AhPAL2), which had large number of ABRE, WUN, and ARE elements in the promoter, played a strong role in response to A. flavus stress.

Isolation and Identification of Allelopathic Substances from Forsythia suspensa Leaves, and Their Metabolism and Activity

The fruit of Forsythia suspensa (Thunb.) Vahl has been used in traditional Chinese medicine as "Forsythiae fructus". The species is also grown in parks and gardens, and on streets and building lots, as an ornamental plant, but it requires pruning. In this study, the allelopathic activity and allelopathic substances in the leaves of pruned branches of F. suspensa were investigated to determine any potential application. The leaf extracts of F. suspensa showed growth inhibitory activity against three weed species; Echinochloa crus-galli, Lolium multiflorum, and Vulpia myuros. Two allelopathic substances in the extracts were isolated through the bioassay-guided purification process, and identified as (-)-matairesinol and (-)-arctigenin. (-)-Matairesinol and (-)-arctigenin, which showed significant growth inhibitory activity at concentrations greater than 0.3 mM in vitro. The inhibitory activity of (-)-arctigenin was greater than that of (-)-matairesinol. However, both compounds were more active than (+)-pinolesinol which is their precursor in the biosynthetic pathway. The investigation suggests that F. suspensa leaves are allelopathic, and (-)-matairesinol and (-)-arctigenin may contribute to the growth inhibitory activities. Therefore, the leaves of the pruned branches can be applied as a weed management strategy in some agricultural practices such as using the leaf extracts in a foliar spray and the leaves in a soil mixture, thereby reducing the dependency on synthetic herbicides in the crop cultivation and contributing to developing eco-friendly agriculture.

Trichoderma cf. asperellum and plant-based titanium dioxide nanoparticles initiate morphological and biochemical modifications in Hordeum vulgare L. against Bipolaris sorokiniana

BACKGROUND

Spot blotch is a serious foliar disease of barley (Hordeum vulgare L.) plants caused by Bipolaris sorokiniana, which is a hemibiotrophic ascomycete that has a global impact on productivity. Some Trichoderma spp. is a promising candidate as a biocontrol agent as well as a plant growth stimulant. Also, the application of nanomaterials in agriculture limits the use of harmful agrochemicals and helps improve the yield of different crops. The current study was carried out to evaluate the effectiveness of Trichoderma. cf. asperellum and the biosynthesized titanium dioxide nanoparticles (TiO2 NPs) to manage the spot blotch disease of barley caused by B. sorokiniana and to assess the plant's innate defense response.

RESULTS

Aloe vera L. aqueous leaf extract was used to biosynthesize TiO2 NPs by reducing TiCl4 salt into TiO2 NPs and the biosynthesized NPs were detected using SEM and TEM. It was confirmed that the NPs are anatase-crystalline phases and exist in sizes ranging from 10 to 25 nm. The T. cf. asperellum fungus was detected using morphological traits and rDNA ITS analysis. This fungus showed strong antagonistic activity against B. sorokiniana (57.07%). Additionally, T. cf. asperellum cultures that were 5 days old demonstrated the best antagonistic activity against the pathogen in cell-free culture filtrate. Also, B. sorokiniana was unable to grow on PDA supplemented with 25 and 50 mg/L of TiO2 NPs, and the diameter of the inhibitory zone increased with increasing TiO2 NPs concentration. In an in vivo assay, barley plants treated with T. cf. asperellum or TiO2 NPs were used to evaluate their biocontrol efficiency against B. sorokiniana, in which T. cf. asperellum and TiO2 NPs enhanced the growth of the plant without displaying disease symptoms. Furthermore, the physiological and biochemical parameters of barley plants treated with T. cf. asperellum or TiO2 NPs in response to B. sorokiniana treatment were quantitively estimated. Hence, T. cf. asperellum and TiO2 NPs improve the plant's tolerance and reduce the growth inhibitory effect of B. sorokiniana.

CONCLUSION

Subsequently, T. cf. asperellum and TiO2 NPs were able to protect barley plants against B. sorokiniana via enhancement of chlorophyll content, improvement of plant health, and induction of the barley innate defense system. The present work emphasizes the major contribution of T. cf. asperellum and the biosynthesized TiO2 NPs to the management of spot blotch disease in barley plants, and ultimately to the enhancement of barley plant quality and productivity.

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

Hypothetical biosynthetic pathways of pharmaceutically potential hallucinogenic metabolites in Myristicaceae, mechanistic convergence and co-evolutionary trends in plants and humans

The family Myristicaceae harbour mind-altering phenylpropanoids like myristicin, elemicin, safrole, tryptamine derivatives such as N,N-dimethyltryptamine (DMT) and 5-methoxy N,N-dimethyltryptamine (5-MeO-DMT) and β-carbolines such as 1-methyl-6-methoxy-dihydro-β-carboline and 2-methyl-6-methoxy-1,2,3,4-tetrahydro-β-carboline. This study aimed to systematically review and propose the hypothetical biosynthetic pathways of hallucinogenic metabolites of Myristicaceae which have the potential to be used pharmaceutically. Relevant publications were retrieved from online databases, including Google Scholar, PubMed Central, Science Direct and the distribution of the hallucinogens among the family was compiled. The review revealed that the biosynthesis of serotonin in plants was catalysed by tryptamine 5-hydroxylase (T5H) and tryptophan 5-hydroxylase (TPH), whereas in invertebrates and vertebrates only by tryptophan 5-hydroxylase (TPH). Indolethylamine-N-methyltransferase catalyses the biosynthesis of DMT in plants and the brains of humans and other mammals. Caffeic acid 3-O-methyltransferase catalyses the biosynthesis of both phenylpropanoids and tryptamines in plants. All the hallucinogenic markers exhibited neuropsychiatric effects in humans as mechanistic convergence. The review noted that DMT, 5-MeO-DMT, and β-carbolines were natural protectants against both plant stress and neurodegenerative human ailments. The protein sequence data of tryptophan 5-hydroxylase and tryptamine 5-hydroxylase retrieved from NCBI showed a co-evolutionary relationship in between animals and plants on the phylogenetic framework of a Maximum Parsimony tree. The review also demonstrates that the biosynthesis of serotonin, DMT, 5-MeO-DMT, 5-hydroxy dimethyltryptamine, and β-carbolines in plants, as well as endogenous secretion of these compounds in the brain and blood of humans and rodents, reflects co-evolutionary mutualism in plants and humans.

Insights to Phenylalanine Ammonia Lyase (PAL) and Secondary Metabolism in Orchids: An in silico Approach

The phenylalanine ammonia lyase (PAL) catalyses the first step of phenylpropanoid metabolic pathway which leads to the biosynthesis of a diverse group of secondary metabolites. Orchids serve as a rich source of metabolites and the availability of genome or transcriptome for selected orchid species provides an opportunity to analyse the PAL genes in orchids. In the present study, 21 PAL genes were characterized using bioinformatics tools in nine orchid species (Apostasia shenzhenica, Cypripedium formosanum, Dendrobium catenatum, Phalaenopsis aphrodite, Phalaenopsis bellina, Phalaenopsis equestris, Phalaenopsis lueddemanniana, Phalaenopsis modesta and Phalaenopsis schilleriana). Multiple sequence alignment confirmed the presence of PAL-specific conserved domains (N-terminal, MIO, core, shielding and C-terminal domain). All these proteins were predicted to be hydrophobic in nature and to have cytoplasmic localisation. Structural modelling depicted the presence of alpha helices, extended strands, beta turns and random coils in their structure. Ala-Ser-Gly triad known for substrate binding and catalysis of MIO-domain was found to be completely conserved in all the proteins. Phylogenetic study showed that the PALs of pteridophytes, gymnosperms and angiosperms clustered together in separate clades. Expression profiling showed tissue-specific expression for all the 21 PAL genes in the various reproductive and vegetative tissues which suggested their diverse role in growth and development. This study provides insights to the molecular characterization of PAL genes which may help in developing biotechnological strategies to enhance the synthesis of phenylpropanoids in orchids and other heterologous systems for pharmaceutical applications.

Eggplant transcription factor SmMYB5 integrates jasmonate and light signaling during anthocyanin biosynthesis

Low light conditions severely suppress anthocyanin synthesis in fruit skins, leading to compromised fruit quality in eggplant (Solanum melongena L.) production. In this study, we found that exogenous methyl-jasmonate (MeJA) application can effectively rescue the poor coloration of the eggplant pericarp under low light conditions. However, the regulatory relationship between jasmonate and light signaling for regulating anthocyanin synthesis remains unclear. Here, we identified a JA response factor, SmMYB5, as an anthocyanin positive regulator by applying RNA-sequencing and characterization of transgenic plants. Firstly, we resolved that SmMYB5 can interact with TRANSPARENT TESTA8 (SmTT8), an anthocyanin-promoted BASIC HELIX-LOOP-HELIX (bHLH) transcription factor, to form the SmMYB5-SmTT8 complex and activate CHALCONE SYNTHASE (SmCHS), FLAVANONE-3-HYDROXYLASE (SmF3H), and ANTHOCYANIN SYNTHASE (SmANS) promoters by direct binding. Secondly, we revealed that JA signaling repressors JASMONATE ZIM DOMAIN5 (SmJAZ5) and SmJAZ10 can interfere with the stability and transcriptional activity of SmMYB5-SmTT8 by interacting with SmMYB5. JA can partially rescue the transcriptional activation of SmF3H and SmANS promoters by inducing SmJAZ5/10 degradation. Thirdly, we demonstrated that the protein abundance of SmMYB5 is regulated by light. CONSTITUTIVELY PHOTOMORPHOGENIC1 (SmCOP1) interacts with SmMYB5 to trigger SmMYB5 degradation via the 26S proteasome pathway. Finally, we delineated a light-dependent JA-SmMYB5 signaling pathway that promotes anthocyanin synthesis in eggplant fruit skins. These results provide insights into the mechanism of the integration of JA and light signals in regulating secondary metabolite synthesis in plants.

Characterization and analysis of multi-organ full-length transcriptomes in Sphaeropteris brunoniana and Alsophila latebrosa highlight secondary metabolism and chloroplast RNA editing pattern of tree ferns

BACKGROUND

Sphaeropteris brunoniana and Alsophila latebrosa are both old relict and rare tree ferns, which have experienced the constant changes of climate and environment. However, little is known about their high-quality genetic information and related research on environmental adaptation mechanisms of them. In this study, combined with PacBio and Illumina platforms, transcriptomic analysis was conducted on the roots, rachis, and pinna of S. brunoniana and A. latebrosa to identify genes and pathways involved in environmental adaptation. Additionally, based on the transcriptomic data of tree ferns, chloroplast genes were mined to analyze their gene expression levels and RNA editing events.

RESULTS

In the study, we obtained 11,625, 14,391 and 10,099 unigenes of S. brunoniana root, rachis, and pinna, respectively. Similarly, a total of 13,028, 11,431 and 12,144 unigenes were obtained of A. latebrosa root, rachis, and pinna, respectively. According to the enrichment results of differentially expressed genes, a large number of differentially expressed genes were enriched in photosynthesis and secondary metabolic pathways of S. brunoniana and A. latebrosa. Based on gene annotation results and phenylpropanoid synthesis pathways, two lignin synthesis pathways (H-lignin and G-lignin) were characterized of S. brunoniana. Among secondary metabolic pathways of A. latebrosa, three types of WRKY transcription factors were identified. Additionally, based on transcriptome data obtained in this study, reported transcriptome data, and laboratory available transcriptome data, positive selection sites were identified from 18 chloroplast protein-coding genes of four tree ferns. Among them, RNA editing was found in positive selection sites of four tree ferns. RNA editing affected the protein secondary structure of the rbcL gene. Furthermore, the expression level of chloroplast genes indicated high expression of genes related to the chloroplast photosynthetic system in all four species.

CONCLUSIONS

Overall, this work provides a comprehensive transcriptome resource of S. brunoniana and A. latebrosa, laying the foundation for future tree fern research.

Simple phenylpropanoids: recent advances in biological activities, biosynthetic pathways, and microbial production

Covering: 2000 to 2023Simple phenylpropanoids are a large group of natural products with primary C6-C3 skeletons. They are not only important biomolecules for plant growth but also crucial chemicals for high-value industries, including fragrances, nutraceuticals, biomaterials, and pharmaceuticals. However, with the growing global demand for simple phenylpropanoids, direct plant extraction or chemical synthesis often struggles to meet current needs in terms of yield, titre, cost, and environmental impact. Benefiting from the rapid development of metabolic engineering and synthetic biology, microbial production of natural products from inexpensive and renewable sources provides a feasible solution for sustainable supply. This review outlines the biological activities of simple phenylpropanoids, compares their biosynthetic pathways in different species (plants, bacteria, and fungi), and summarises key research on the microbial production of simple phenylpropanoids over the last decade, with a focus on engineering strategies that seem to hold most potential for further development. Moreover, constructive solutions to the current challenges and future perspectives for industrial production of phenylpropanoids are presented.

Recent advancements in multifaceted roles of flavonoids in plant-rhizomicrobiome interactions

The rhizosphere consists of a plethora of microbes, interacting with each other as well as with the plants present in proximity. The root exudates consist of a variety of secondary metabolites such as strigolactones and other phenolic compounds such as coumarin that helps in facilitating communication and forming associations with beneficial microbes in the rhizosphere. Among different secondary metabolites flavonoids (natural polyphenolic compounds) continuously increasing attention in scientific fields for showing several slews of biological activities. Flavonoids possess a benzo-γ-pyrone skeleton and several classes of flavonoids have been reported on the basis of their basic structure such as flavanones, flavonols, anthocyanins, etc. The mutualistic association between plant growth-promoting rhizobacteria (PGPR) and plants have been reported to help the host plants in surviving various biotic and abiotic stresses such as low nitrogen and phosphorus, drought and salinity stress, pathogen attack, and herbivory. This review sheds light upon one such component of root exudate known as flavonoids, which is well known for nodulation in legume plants. Apart from the well-known role in inducing nodulation in legumes, this group of compounds has anti-microbial and antifungal properties helping in establishing defensive mechanisms and playing a major role in forming mycorrhizal associations for the enhanced acquisition of nutrients such as iron and phosphorus. Further, this review highlights the role of flavonoids in plants for recruiting non-mutualistic microbes under stress and other important aspects regarding recent findings on the functions of this secondary metabolite in guiding the plant-microbe interaction and how organic matter affects its functionality in soil.

Genome-wide association study of kernel colour traits and mining of elite alleles from the major loci in maize

BACKGROUND

Maize kernel colour is an important index for evaluating maize quality and value and mainly entails two natural pigments, carotenoids and anthocyanins. To analyse the genetic mechanism of maize kernel colour and mine single nucleotide polymorphisms (SNPs) related to kernel colour traits, an association panel including 244 superior maize inbred lines was used to measure and analyse the six traits related to kernel colour in two environments and was then combined with the about 3 million SNPs covering the whole maize genome in this study. Two models (Q + K, PCA + K) were used for genome-wide association analysis (GWAS) of kernel colour traits.

RESULTS

We identified 1029QTLs, and two SNPs contained in those QTLs were located in coding regions of Y1 and R1 respectively, two known genes that regulate kernel colour. Fourteen QTLs which contain 19 SNPs were within 200 kb interval of the genes involved in the regulation of kernel colour. 13 high-confidence SNPs repeatedly detected for specific traits, and AA genotypes of rs1_40605594 and rs5_2392770 were the most popular alleles appeared in inbred lines with higher levels. By searching the confident interval of the 13 high-confidence SNPs, a total of 95 candidate genes were identified.

CONCLUSIONS

The genetic loci and candidate genes of maize kernel colour provided in this study will be useful for uncovering the genetic mechanism of maize kernel colour, gene cloning in the future. Furthermore, the identified elite alleles can be used to molecular marker-assisted selection of kernel colour traits.

A cytosine analogue 5-azacitidine improves the accumulation of licochalcone A in licorice Glycyrrhiza inflata

Licochalcone A (LCA) is a characteristic compound of Glycyrrhiza inflata with anti-inflammatory, antioxidant and antitumor activities. However, G. inflata produces LCA in low quantities that does not meet the market demand. In this study, we found that DNA methylation inhibitor 5-azacitidine (5-azaC) successfully improved the LCA contents in G. inflata seedlings. Transcriptome analysis revealed a series of differentially expressed genes (DEGs), including transcription factors such as MYB, ERF, WRKY, and some structural genes related to flavonoid biosynthesis. However, whole genome bisulfite sequencing (BS-seq) results showed little effect of the 5-azaC treatment on the alteration of DNA methylation on these genes, indicating the possibility that 5-azaC acts as a stimulus, but not an epigenetic modulation factor to improve the LCA content in G. inflata. Additionally, we applied the 5-azaC treatment to field plants and hairy roots and successfully increased the LCA contents in both cases. This research demonstrates the feasibility of 5-azaC treatments in future applications to improve plant production of LCA.

Signaling in Legume-Rhizobia Symbiosis

Legumes represent an important source of food protein for human nutrition and animal feed. Therefore, sustainable production of legume crops is an issue of global importance. It is well-known that legume-rhizobia symbiosis allows an increase in the productivity and resilience of legume crops. The efficiency of this mutualistic association strongly depends on precise regulation of the complex interactions between plant and rhizobia. Their molecular dialogue represents a complex multi-staged process, each step of which is critically important for the overall success of the symbiosis. In particular, understanding the details of the molecular mechanisms behind the nodule formation and functioning might give access to new legume cultivars with improved crop productivity. Therefore, here we provide a comprehensive literature overview on the dynamics of the signaling network underlying the development of the legume-rhizobia symbiosis. Thereby, we pay special attention to the new findings in the field, as well as the principal directions of the current and prospective research. For this, here we comprehensively address the principal signaling events involved in the nodule inception, development, functioning, and senescence.

Anabolic metabolism of autotoxic substance coumarins in plants

Background

Autotoxicity is an intraspecific manifestation of allelopathy in plant species. The specialized metabolites and their derivatives that cause intraspecific allelopathic inhibition in the plant are known as autotoxic substances. Consequently, autotoxic substances production seriously affects the renewal and stability of ecological communities.

Methods

This article systematically summarizes the types of autotoxic substances present in different plants. They mainly include phenolic compounds, terpenoids, and nitrogenous organic compounds. Phenolic coumarins are the main autotoxic substances in many plants. Therefore, we also discuss differences in coumarin types and content among plant varieties, developmental stages, and tissue parts, as well as their mechanisms of autotoxicity. In addition, we review the metabolic pathways involved in coumarin biosynthesis, the key enzymes, genes, and transcription factors, as well as factors affecting coumarin biosynthesis.

Results

Coumarin biosynthesis involves three stages: (1) the formation of the coumarin nucleus; (2) acylation, hydroxylation, and cyclization; (3) structural modification. The key enzymes involved in the coumarin nuclear formation stage include PAL, C4H, 4CL, HCT, CAOMT, COSY, F6'H, and CCoAOMT1, and the key genes involved include BGA, CYP450 and MDR, among others. Ortho-hydroxylation is a key step in coumarin biosynthesis and PS, COSY and S8H are the key enzymes involved in this process. Finally, UGTs are responsible for the glycosylation modification of coumarins, and the MaUGT gene may therefore be involved in coumarin biosynthesis.

Conclusion

It is important to elucidate the autotoxicity and anabolic mechanisms of coumarins to create new germplasms that produce fewer autotoxic substances.

Pour some sugar on me: The diverse functions of phenylpropanoid glycosylation

The phenylpropanoid metabolism is the source of a vast array of specialized metabolites that play diverse functions in plant growth and development and contribute to all aspects of plant interactions with their surrounding environment. These compounds protect plants from damaging ultraviolet radiation and reactive oxygen species, provide mechanical support for the plants to stand upright, and mediate plant-plant and plant-microorganism communications. The enormous metabolic diversity of phenylpropanoids is further expanded by chemical modifications known as "decorative reactions", including hydroxylation, methylation, glycosylation, and acylation. Among these modifications, glycosylation is the major driving force of phenylpropanoid structural diversification, also contributing to the expansion of their properties. Phenylpropanoid glycosylation is catalyzed by regioselective uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs), whereas glycosyl hydrolases known as β-glucosidases are the major players in deglycosylation. In this article, we review how the glycosylation process affects key physicochemical properties of phenylpropanoids, such as molecular stability and solubility, as well as metabolite compartmentalization/storage and biological activity/toxicity. We also summarize the recent knowledge on the functional implications of glycosylation of different classes of phenylpropanoid compounds. A balance of glycosylation/deglycosylation might represent an essential molecular mechanism to regulate phenylpropanoid homeostasis, allowing plants to dynamically respond to diverse environmental signals.

Analysis of the effects of sulfamethoxazole on the secondary metabolites and antioxidants in oilseed rape (Brassica napus L.) and the underlying mechanisms

The secondary metabolism of plants is key for mediating responses to environmental stress, but few studies have examined how the relationship between secondary metabolism and the stress response of plants is affected by exposure to antibiotics. Here, we studied the effects of sulfamethoxazole (SMZ) on the secondary metabolism and antioxidant activity of oilseed rape (Brassica napus L.). SMZ significantly affected the growth of rape seedlings. Low and high concentrations of SMZ induced the production of a large number of reactive oxygen species (ROS) in rape seedlings, which damaged cells. SMZ stress altered the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as the content of malondialdehyde (MDA). SMZ promoted the activities of phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL), cinnamic acid-4-hydroxylase (C4H), and 4-coumaric acid: coenzyme A ligase (4CL) by activating the phenylpropanoid pathway. The content of secondary metabolites changed. The content of phenolic acids and flavonoids increased, and the content of sinapine and anthocyanins was altered to cope with the oxidative damage induced by antibiotics. Transcriptomic and metabolomic analysis showed that differentially expressed genes and differentially expressed metabolites were mainly involved in Phenylpropanoid biosynthesis. SMZ alters the secondary metabolites of rapeseed, which mitigates the deleterious effects of stress, by modulating upstream secondary metabolism pathways and the production of plant hormones involved in signal transduction. In sum, these results provide a new perspective on the effects of SMZ on plants relative to secondary metabolites and improve our understanding of the toxicity of SMZ.

The Interactions between Two Fungal Endophytes Epicoccum layuense R2-21 and Alternaria alternata XHYN2 and Grapevines (Vitis vinifera) with De Novo Established Symbionts under Aseptic Conditions

In this study, we focused on grapevine-endophyte interactions and reprogrammed secondary metabolism in the host plant due to defense against the colonization of endophytes. Thus, the transcriptional responses of tissue cultured grapevine seedlings (Vitis vinifera L. cv.: Cabernet Sauvignon) to two fungal endophytes Epicoccum layuense R2-21 (Epi R2-21) and Alternaria alternata XHYN2 (Alt XHYN2) at three different time points (6 h, 6 d, 15 d) were analyzed. As expected, a total of 5748 and 5817 differentially expressed genes (DEGs) were separately initiated in Epi R2-21 and Alt XHYN2 symbiotic tissue cultured seedlings compared to no endophyte treatment. The up-regulated DEGs at all time points in Epi R2-21- or Alt XHYN2-treated seedlings were mainly enriched in the flavonoid biosynthesis, phenylpropanoid biosynthesis, phenylalanine metabolism, stilbenoid, diarylheptanoid and gingerol biosynthesis, and circadian rhythm-plant pathways. In addition, the up-regulated DEGs at all sampling times in Alt XHYN2-treated tissue cultured seedlings were enriched in the plant-pathogen interaction pathway, but appeared in Epi R2-21 symbiotic seedlings only after 15 d of treatment. The down-regulated DEGs were not enriched in any KEGG pathways after 6 h inoculation for Epi R2-21 and Alt XHYN2 treatments, but were enriched mainly in photosynthesis-antenna proteins and plant hormone signal transduction pathways at other sampling times. At three different time points, a total of 51 DEGs (all up-regulated, 1.33-10.41-fold) were involved in secondary metabolism, and 22 DEGs (all up-regulated, 1.01-8.40-fold) were involved in defense responses in endophytic fungi symbiotic tissue cultured seedlings. The protein-protein interaction (PPI) network demonstrated that genes encoding CHS (VIT_10s0042g00920, VIT_14s0068g00920, and VIT_16s0100g00910) and the VIT_11s0065g00350 gene encoding CYP73A mediated the defense responses, and might induce more defense-associated metabolites. These results illustrated the activation of stress-associated secondary metabolism in the host grapevine during the establishment of fungi-plant endophytism. This work provides avenues for reshaping the qualities and characteristics of wine grapes utilizing specific endophytes and better understanding plant-microbe interactions.

Effects of salicylic acid-grafted bamboo hemicellulose on gray mold control in blueberry fruit: The phenylpropanoid pathway and peel microbial community composition

Bamboo hemicellulose (HC) is a natural plant polysaccharide with good biocompatibility and biodegradability. But its poor antibacterial activity limits its application in fruits preservation. In this study, based on the good inducer of salicylic acid (SA) for plant diseases resistance, a novel antibacterial coating material was synthesized by grafting SA onto HC. The study aimed to investigate the synergistic effect of HC-g-SA on antibacterial ability, induces diseases resistance and microbial community composition of postharvest fruit. The graft copolymer treatment significantly reduced the incidence of gray mold caused by Botrytis cinerea in blueberries during storage (P < 0.05), and significantly stimulated the activity of key enzymes, including phenylalanine ammonia-lyase, chalcone isomerase, laccase, and polyphenol oxidase, leading to an increase in fungicidal compounds such as flavonoids, lignin, and total phenolics produced by the phenylpropanoid pathway in blueberries (P < 0.05). Moreover, the HC-g-SA coating altered bacterial and fungal community composition such that the abundance of postharvest fruit-peel pathogens was significantly reduced. After 8 days storage, the blueberry fruits treated by HC-g-SA had a weight loss rate of 12.42 ± 0.85 %. Therefore, the HC-g-SA graft copolymer had a positive impact on the control of gray mold in blueberry fruit during postharvest storage.

Lipidomics analysis reveals the effect of Sirex noctilio infestation on the lipid metabolism in Pinus radiata needles

The Sirex noctilio's climatic adaption and rapid proliferation have caused Pinus mortality worldwide. The infestation combines the early effect of female S. noctilio gland secretion and the spreading symbiotic fungus Amylostereum areolatum. 'Lipidomics' is the study of all non-water-soluble components of the metabolome. Most of these non-water-soluble compounds correspond to lipids which can provide information about a biological activity, an organelle, an organism, or a disease. Using HPLC-MS/MS based lipidomics, 122 lipids were identified in P. radiata needles during S. noctilio infestation. Phosphatidic acids, N-acylethanolamines, and phosphatidylinositol-ceramides accumulated in infested trees could suggest a high level of phospholipases activities. The phosphatidylcholines were the most down-regulated species during infection, which could also suggest that they may be used as a substrate for up-regulated lipids. The accumulation of very long-chain fatty acids and long-chain fatty acids during the infestation could imply the tree defense response to create a barrier in the drilled zone to avoid larvae development and fungus proliferation. Also, the growth arrest phase of the trees during the prolonged infestation suggests a resistance response, regulated by the accumulation of NAE, which potentially shifts the tree energy to respond to the infestation.

Research on the Effect of Oriental Fruit Moth Feeding on the Quality Degradation of Chestnut Rose Juice Based on Metabolomics

As a native fruit of China, chestnut rose (Rosa roxburghii Tratt) juice is rich in bioactive ingredients. Oriental fruit moth (OFM), Grapholita molesta (Busck), attacks the fruits and shoots of Rosaceae plants, and its feeding affects the quality and yield of chestnut rose. To investigate the effects of OFM feeding on the quality of chestnut rose juice, the bioactive compounds in chestnut rose juice produced from fruits eaten by OFM were measured. The electronic tongue senses, amino acid profile, and untargeted metabolomics assessments were performed to explore changes in the flavour and metabolites. The results showed that OFM feeding reduced the levels of superoxide dismutase (SOD), tannin, vitamin C, flavonoid, and condensed tannin; increased those of polyphenols, soluble solids, total protein, bitterness, and amounts of bitter amino acids; and decreased the total amino acid and umami amino acid levels. Furthermore, untargeted metabolomics annotated a total of 426 differential metabolites (including 55 bitter metabolites), which were mainly enriched in 14 metabolic pathways, such as flavonoid biosynthesis, tryptophan metabolism, tyrosine metabolism, and diterpenoid biosynthesis. In conclusion, the quality of chestnut rose juice deteriorated under OFM feeding stress, the levels of bitter substances were significantly increased, and the bitter taste was subsequently enhanced.

De novo sequencing, assembly, and characterization of Asparagus racemosus transcriptome and analysis of expression profile of genes involved in the flavonoid biosynthesis pathway

Asparagus racemosus is known for its diverse content of secondary metabolites, i.e., saponins, alkaloids, and a wide range of flavonoids. Flavonoids, including phenols and polyphenols, have a significant role in plant physiology and are synthesized in several tissues. Despite the diverse role of flavonoids, genetic information is limited for flavonoid biosynthesis pathways in A. racemosus. The current study explores full-scale functional genomics information of A. racemosus by de novo transcriptome sequencing using Illumina paired-end sequencing technology to elucidate the genes involved in flavonoid biosynthesis pathways. The de novo assembly of high-quality paired-end reads resulted in ∼2.3 million high-quality reads with a pooled transcript of 45,647 comprising ∼76 Mb transcriptome with a mean length (bp) of 1,674 and N50 of 1,868bp. Furthermore, the coding sequence (CDS) prediction analysis from 45,647 pooled transcripts resulted in 45,444 CDS with a total length and mean length of 76,398,686 and 1,674, respectively. The Gene Ontology (GO) analysis resulted in a high number of CDSs assigned to 25,342 GO terms, which grouped the predicted CDS into three main domains, i.e., Biological Process (19,550), Molecular Function (19,873), and Cellular Component (14,577). The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database was used to categorize 6,353 CDS into 25 distinct biological pathway categories, in which the majority of mapped CDS were shown to be related to translation (645), followed by signal transduction (532), carbohydrate metabolism (524), folding, sorting, and degradation (522). Among these, only ∼64 and 14 CDSs were found to be involved in the phenylpropanoid and flavonoid biosynthesis pathways, respectively. Quantitative Real-time PCR was used to check the expression profile of fourteen potential flavonoid biosynthesis pathway genes. The qRT-PCR analysis result matches the transcriptome sequence data validating the Illumina sequence results. Moreover, a large number of genes associated with the flavonoids biosynthesis pathway were found to be upregulated under the induction of methyl jasmonate. The present-day study on transcriptome sequence data of A. racemosus can be utilized for characterizing genes involved in flavonoid biosynthesis pathways and for functional genomics analysis in A. racemosus using the reverse genetics approach (CRISPR/Cas9 technology).

Integrative HPLC profiling and transcriptome analysis revealed insights into anthocyanin accumulation and key genes at three developmental stages of black rice (Oryza sativa. L) caryopsis

Introduction

Anthocyanins are plants' secondary metabolites belonging to the flavonoid class with potential health-promoting properties. They are greatly employed in the food industry as natural alternative food colorants for dairy and ready-to-eat desserts and pH indicators. These tremendous advantages make them economically important with increasing market trends. Black rice is a rich source of anthocyanin that can be used to ensure food and nutritional security around the world. However, research on anthocyanin accumulation and gene expression during rice caryopsis development is lacking.

Methods

In this study, we combined high-performance liquid chromatography (HPLC) and transcriptome analysis to profile the changes in anthocyanin content and gene expression dynamics at three developmental stages (milky, doughy, and mature).

Results

Our results showed that anthocyanin accumulation started to be visible seven days after flowering (DAF), increased rapidly from milky (11 DAF) to dough stage, then started decreasing after the peak was attained at 18 DAF. RNA-seq showed that 519 out of 14889, 477 out of 17914, and 1614 out of 18810 genes were uniquely expressed in the milky, doughy, and mature stages, respectively. We performed three pairwise comparisons: milky vs. dough, milky vs. mature, and dough vs. mature, and identified 6753, 9540, and 2531 DEGs, respectively. The DEGs' abundance was higher in milky vs. mature, with 5527 up-regulated genes and 4013 down-regulated genes, while it was smaller in dough vs. mature, with 1419 up-regulated genes and 1112 down-regulated DEGs. This result was consistent with the changes in anthocyanin profiling, and the expression of structural, regulatory, and transporter genes involved in anthocyanin biosynthesis showed their highest expression at the dough stage. Through the gene expression profile and protein interaction network, we deciphered six main contributors of the anthocyanin peak observed at dough stage, including OsANS, OsDFR, OsGSTU34, OsMYB3, OsbHLH015, and OsWD40-50.

Discussion

This study is the first to report the investigation of anthocyanin and gene expression at three developmental stages of black rice caryopsis. The findings of this study could aid in predicting the best harvesting time to achieve maximum anthocyanin content and the best time to collect samples for various gene expression analysis, laying the groundwork for future research into the molecular mechanisms underlying rice caryopsis coloration.

Anthocyanin metabolism and its differential regulation in purple tea (Camellia sinensis)

Tea plants (Camellia sinensis) typically contain high-flavonoid phytochemicals like catechins. Recently, new tea cultivars with unique purple-colored leaves have gained attention. These purple tea cultivars are enriched with anthocyanin, which provides an interesting perspective for studying the metabolic flux of the flavonoid pathway. An increasing number of studies are focusing on the leaf color formation of purple tea and this review aims to summarize the latest progress made on the composition and accumulation of anthocyanins in tea plants. In addition, the regulation mechanism in its synthesis will be discussed and a hypothetical regulation model for leaf color transformation during growth will be proposed. Some novel insights are presented to facilitate future in-depth studies of purple tea to provide a theoretical basis for targeted breeding programs in leaf color.

Comprehensive analysis of lncRNA-mRNA regulatory network in Populus associated with xylem development

Long noncoding RNAs (lncRNAs) play essential roles in numerous biological processes in plants, such as regulating the gene expression. However, only a few studies have looked into their potential functions in xylem development. High-throughput sequencing of P. euramericana 'Zhonglin46' developing and mature xylem was performed in this study. Through sequencing analysis, 14,028 putative lncRNA transcripts were identified, including 4525 differentially expressed lncRNAs (DELs). Additional research revealed that in mature xylem, a total of 2320 DELs were upregulated and 2205 were downregulated compared to developing xylem. Meanwhile, there were a total of 8122 differentially expressed mRNAs (DEMs) that were upregulated and 16,424 that were downregulated in mature xylem compared with developing xylem. The cis- and trans-target genes of DELs were analyzed for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, which indicated that these DELs participate in controlling the phenylpropanoid and lignin biosynthesis pathway as well as the starch and sucrose metabolism pathway. Among the cis-regulated DELs, LNC_006291, LNC_006292, and LNC_006532 all participate in regulating multiple HCT gene family membranes. As targets, POPTR_001G045900v3 (CCR2) and POPTR_018G063500v3 (SUS) both have only one cis-regulatory lncRNA, referred to as LNC_000057 and LNC_006212, respectively. Moreover, LNC_004484 and two DELs named LNC_008014 and LNC_010781 were revealed to be important nodes in the co-expression network of trans-lncRNAs and mRNAs associated to the lignin biosynthesis pathway and cellulose and xylan biosynthetic pathways, respectively. Finally, quantitative real-time PCR (qRT-PCR) was used to confirme 34 pairs of lncRNA-mRNA. Taken together, these findings may help to clarify the regulatory role that lncRNAs play in xylem development and wood formation.

Spiro-Flavonoids in Nature: A Critical Review of Structural Diversity and Bioactivity

Based on the literature data from 1973 to 2022, this work summarizes reports on spiro-flavonoids with a spiro-carbon at the center of their structure and how this affects their isolation methods, stereochemistry, and biological activity. The review collects 65 unique structures, including spiro-biflavonoids, spiro-triflavonoids, spiro-tetraflavonoids, spiro-flavostilbenoids, and scillascillin-type homoisoflavonoids. Scillascillin-type homoisoflavonoids comprise spiro[bicyclo[4.2.0]octane-7,3'-chromane]-1(6),2,4-trien-4'-one, while the other spiro-flavonoids contain either 2H,2'H-3,3'-spirobi[benzofuran]-2-one or 2'H,3H-2,3'-spirobi[benzofuran]-3-one in the core of their structures. Spiro-flavonoids have been described in more than 40 species of eight families, including Asparagaceae, Cistaceae, Cupressaceae, Fabaceae, Pentaphylacaceae, Pinaceae, Thymelaeaceae, and Vitaceae. The possible biosynthetic pathways for each group of spiro-flavonoids are summarized in detail. Anti-inflammatory and anticancer activities are the most important biological activities of spiro-flavonoids, both in vitro and in vivo. Our work identifies the most promising natural sources, the existing challenges in assigning the stereochemistry of these compounds, and future research perspectives.

ABA Biosynthesis- and Signaling-Related Gene Expression Differences between Sweet Cherry Fruits Suggest Attenuation of ABA Pathway in Bicolored Cultivars

Fruit development involves exocarp color evolution. However, signals that control this process are still elusive. Differences between dark-red and bicolored sweet cherry cultivars rely on MYB factor gene mutations. Color evolution in bicolored fruits only occurs on the face receiving sunlight, suggesting the perception or response to color-inducing signals is affected. These color differences may be related to synthesis, perception or response to abscisic acid (ABA), a phytohormone responsible for non-climacteric fruit coloring. This work aimed to determine the involvement of ABA in the coloring process of color-contrasting varieties. Several phenolic accumulation patterns differed between bicolored 'Royal Rainier' and dark-red 'Lapins'. Transcript abundance of ABA biosynthetic genes (PavPSY, PavZEP and PavNCED1) decreased dramatically from the Pink to Red stage in 'Royal Rainier' but increased in 'Lapins', which correlated with a higher ABA content in this dark-red cultivar. Transcripts coding for ABA signaling (PavPP2Cs, PavSnRKs and PavMYB44.1) were almost undetectable at the Red stage in 'Royal Rainier'. Field trials revealed that 'Royal Rainier' color development was insensitive to exogenous ABA, whereas it increased in 'Lapins'. Furthermore, ABA treatment only increased transcript levels of signaling genes in 'Lapins'. Further studies may address if the ABA pathway is attenuated in bicolor cultivars.

Syntaxin of plants71 plays essential roles in plant development and stress response via regulating pH homeostasis

SYP71, a plant-specific Qc-SNARE with multiple subcellular localization, is essential for symbiotic nitrogen fixation in nodules in Lotus, and is implicated in plant resistance to pathogenesis in rice, wheat and soybean. Arabidopsis SYP71 is proposed to participate in multiple membrane fusion steps during secretion. To date, the molecular mechanism underlying SYP71 regulation on plant development remains elusive. In this study, we clarified that AtSYP71 is essential for plant development and stress response, using techniques of cell biology, molecular biology, biochemistry, genetics, and transcriptomics. AtSYP71-knockout mutant atsyp71-1 was lethal at early development stage due to the failure of root elongation and albinism of the leaves. AtSYP71-knockdown mutants, atsyp71-2 and atsyp71-3, had short roots, delayed early development, and altered stress response. The cell wall structure and components changed significantly in atsyp71-2 due to disrupted cell wall biosynthesis and dynamics. Reactive oxygen species homeostasis and pH homeostasis were also collapsed in atsyp71-2. All these defects were likely resulted from blocked secretion pathway in the mutants. Strikingly, change of pH value significantly affected ROS homeostasis in atsyp71-2, suggesting interconnection between ROS and pH homeostasis. Furthermore, we identified AtSYP71 partners and propose that AtSYP71 forms distinct SNARE complexes to mediate multiple membrane fusion steps in secretory pathway. Our findings suggest that AtSYP71 plays an essential role in plant development and stress response via regulating pH homeostasis through secretory pathway.

Widely targeted metabolomic profiling combined with transcriptome analysis sheds light on flavonoid biosynthesis in sweet orange 'Newhall' (C. sinensis) under magnesium stress

Sweet orange 'Newhall' peels (SOPs) are abundant in flavonoids, making them increasingly popular in the realms of nutrition, food, and medicine. However, there is still much unknown about flavonoid components in SOPs and the molecular mechanism of flavonoid biosynthesis when subjected to magnesium stress. The previous experiment conducted by the research group found that the total flavonoid content of Magnesium deficiency (MD) was higher than Magnesium sufficiency (MS) in SOPs. In order to study the metabolic pathway of flavonoids under magnesium stress, an integrative analysis of the metabolome and transcriptome was performed in SOPs at different developmental stages, comparing MS and MD. A comprehensive analysis revealed the identification of 1,533 secondary metabolites in SOPs. Among them, 740 flavonoids were classified into eight categories, with flavones identified as the dominant flavonoid component. The influence of magnesium stress on flavonoid composition was evaluated using a combination of heat map and volcanic map, which indicated significant variations between MS and MD varieties at different growth stages. The transcriptome detected 17,897 differential genes that were significantly enriched in flavonoid pathways. Further analysis was performed using Weighted gene correlation network analysis (WGCNA) in conjunction with flavonoid metabolism profiling and transcriptome analysis to identify six hub structural genes and ten hub transcription factor genes that play a crucial role in regulating flavonoid biosynthesis from yellow and blue modules. The correlation heatmap and Canonical Correspondence Analysis (CCA) results showed that CitCHS had a significant impact on the synthesis of flavones and other flavonoids in SOPs, as it was the backbone gene in the flavonoid biosynthesis pathway. The qPCR results further validated the accuracy of transcriptome data and the reliability of candidate genes. Overall, these results shed light on the composition of flavonoid compounds in SOPs and highlight the changes in flavonoid metabolism that occur under magnesium stress. This research provides valuable insights for improving the cultivation of high-flavonoid plants and enhancing our understanding of the molecular mechanisms underlying flavonoid biosynthesis.

Transcriptomic analysis reveals that Bacillomycin D-C16 induces multiple pathways of disease resistance in cherry tomato

BACKGROUND

Bacillomycin D-C16 can induce resistance in cherry tomato against pathogens; however, the underlying molecular mechanism is poorly understood. Here, the effect of Bacillomycin D-C16 on induction of disease resistance in cherry tomato was investigated using a transcriptomic analysis.

RESULTS

Transcriptomic analysis revealed a series of obvious enrichment pathways. Bacillomycin D-C16 induced phenylpropanoid biosynthesis pathways and activated the synthesis of defense-related metabolites including phenolic acids and lignin. Moreover, Bacillomycin D-C16 triggered a defense response through both hormone signal transduction and plant-pathogen interactions pathways, and increased the transcription of several transcription factors (e.g., AP2/ERF, WRKY and MYB). These transcription factors might contribute to the further activated the expression of defense-related genes (PR1, PR10 and CHI) and stimulated the accumulation of H2O2.

CONCLUSION

Bacillomycin D-C16 can induce resistance in cherry tomato by activating the phenylpropanoid biosynthesis pathway, hormone signal transduction pathway and plant-pathogen interactions pathway, thus activating comprehensive defense reaction against pathogen invasion. These results provided a new insight into the bio-preservation of cherry tomato by the Bacillomycin D-C16.

Phylogenetic relationship and sequence diversity of candidate genes involved in anthocyanin biosynthesis pathway in Carthamus species with contrasting seed coat colors

The morphological structure of seed such as coat color can be considered as effective parameters in the evaluation of resistance to pests. The present study is aimed at achieving these goals: first, to determine the phylogenetic relationship of different species of safflower with different seed coat colors based on three candidate genes in the anthocyanin biosynthesis pathway that encode the early steps (PAL: phenylalanine ammonia-lyase and CHS: chalcone synthase) and the final step (UFGT: flavonoid-3-O-glucosyltransferase); second, based on our previous study on the absence of cyanidin-3-O-glucoside (Cyd-3-glu) in white/brown-seeded genotypes, it can be determined whether the lack of production is related to the absence of genes or the lack of expression. In general, the detection of Cyd-3-glu upstream compounds in all studied safflower genotypes, regardless of the color of the seed coat, can be interpreted as the expression of genes responsible for the synthesis of these compounds in the anthocyanin synthesis pathway. In addition, these findings indicated that the accumulation pattern of the mentioned secondary metabolites could be varied in safflower genotypes according to the seed coat color pattern. Regarding the UFGT gene, the evidence showed that this gene is expressed in safflower genotypes with two different seed coat color patterns, but in each genotype the tendency to produce secondary metabolites is different. Consequently, it seems that UFGT may not only regulate Cyd-3-glu biosynthesis but also involved in biosynthesis of flavonol glucoside in black safflower. Additionally, UFGT only affected flavonol glycosides biosynthesis and had no effect on Cyd-3-glu biosynthesis in white- seeded safflower genotypes.

Transcriptomic profiling reveals candidate allelopathic genes in rice responsible for interactions with barnyardgrass

Echinochloa crus-galli (barnyardgrass) is one of the most damaging weeds in rice fields worldwide. Allelopathy has been considered a possible application for weed management. Thus understanding its molecular mechanisms is important for rice production. This study generated transcriptomes from rice under mono- and co-culture with barnyardgrass at two-time points to identify the candidate genes controlling allelopathic interactions between rice and barnyardgrass. A total of 5,684 differentially expressed genes (DEGs) were detected, amongst which 388 genes were transcription factors. These DEGs include genes associated with momilactone and phenolic acid biosynthesis, which play critical roles in allelopathy. Additionally, we found significantly more DEGs at 3 hours than at 3 days, suggesting a quick allelopathic response in rice. Up-regulated DEGs involve diverse biological processes, such as response to stimulus and pathways related to phenylpropanoid and secondary metabolites biosynthesis. Down-regulated DEGs were involved in developmental processes, indicating a balance between growth and stress response to allelopathy from barnyardgrass. Comparison of DEGs between rice and barnyardgrass shows few common genes, suggesting different mechanisms underlying allelopathic interaction in these two species. Our results offer an important basis for identifying of candidate genes responsible for rice and barnyardgrass interactions and contribute valuable resources for revealing its molecular mechanisms.

Enhanced UV-B Radiation Induced the Proanthocyanidins Accumulation in Red Rice Grain of Traditional Rice Cultivars and Increased Antioxidant Capacity in Aging Mice

Proanthocyanidins are major UV-absorbing compounds. To clarify the effect of enhanced UV-B radiation on the proanthocyanidin synthesis and antioxidant capacity of traditional rice varieties in Yuanyang terraced fields, we studied the effects of enhanced UV-B radiation (0, 2.5, 5.0, 7.5 kJ·m^-2·d^-1) on the rice grain morphology, proanthocyanidins content, and synthesis. The effects of UV-B radiation on the antioxidant capacity of rice were evaluated by feeding aging model mice. The results showed that UV-B radiation significantly affected the grain morphology of red rice and increased the compactness of starch grains in the starch storage cells of central endosperm. The content of proanthocyanidin B2 and C1 in the grains was significantly increased by 2.5 and 5.0 kJ·m^-2·d^-1 UV-B radiation. The activity of leucoanthocyanidin reductase was higher in rice treated by 5.0 kJ·m^-2·d^-1 than other treatments. The number of neurons in the hippocampus CA1 of mice brain fed red rice increased. After 5.0 kJ·m^-2·d^-1 treatment, red rice has the best antioxidant effect on aging model mice. UV-B radiation induces the synthesis of rice proanthocyanidins B2 and C1, and the antioxidant capacity of rice is related to the content of proanthocyanidins.

Transcriptome Sequencing of Broussonetia papyrifera Leaves Reveals Key Genes Involved in Flavonoids Biosynthesis

Broussonetia papyrifera is rich in flavonoids, which have significant antioxidant, antibacterial, and anti-inflammatory activities and certain pharmacological activities. Nevertheless, scarce transcriptome resources of B. papyrifera have impeded further study regarding the process of its production and accumulation. In this study, RNA-seq was utilized to evaluate the gene expression of B. papyrifera leaves at three distinct developmental phases (T1: young leaves, T3: immature leaves, T4: matured leaves). We obtained 2447 upregulated and 2960 downregulated DEGs, 4657 upregulated and 4804 downregulated DEGs, and 805 upregulated and 484 downregulated DEGs from T1 vs. T3, T1 vs. T4, and T3 vs. T4, respectively. Further research found that the following variables contributed to the formation of flavonoids in the leaves of B. papyrifera: Several important enzyme genes involved in flavonoid production pathways have been discovered. The results demonstrated that the dynamic changing trend of flavonoid contents is related to the expression pattern of the vast majority of essential genes in the biosynthetic pathway. Genes associated in energy and glucose metabolism, polysaccharide, cell wall and cytoskeleton metabolism, signal transduction, and protein and amino acid metabolism may affect the growth and development of B. papyrifera leaves, and eventually their flavonoid content. This study's results offer a strong platform for future research into the metabolic pathways of B. papyrifera.

Low temperature reduces potato wound formation by inhibiting phenylpropanoid metabolism and fatty acid biosynthesis

INTRODUCTION

Potato tubers have the healing capacity to prevent surface water transpiration and pathogen invasion after mechanical damage. Previous research has shown the inability to form healing periderm in potatoes under low temperatures, but the potential mechanism is still unclear.

METHODS

To explore the effects and mechanisms of low-temperature potato healing, wounded potatoes were stored at low temperature (4°C) and room temperature (22°C), respectively.

RESULTS

In this study, compared with 22°C healing, low temperature reduced the content of hydrogen peroxide, and the down-regulation of StAMY23 inhibited the conversion of starch to sugar, alleviated the degradation of starch, and reduced the content of soluble sugars and sucrose. Meanwhile, inhibition of phenylalanine metabolism by suppression of StPAL1 and St4CL expression reduced lignin accumulation. Low temperature also down-regulated the expression of StKCS6, StFAOH, StGPAT5, and StPrx, causing the lower deposition amount of suberin in wounds of potato tubers.

DISCUSSION

The above results suggested that low temperature led to less wound tissue deposition at the wound surfaces via suppressing phenylpropanoid metabolism and fatty acid biosynthesis in potato tubers.

Allelopathic Substances of Osmanthus spp. for Developing Sustainable Agriculture

Osmanthus fragrans Lour. has been cultivated for more than 2500 years because of the fragrance and color of the flowers. The flowers and roots have been used in tea, liquors, foods, and traditional Chinese medicine. The species contains more than 180 compounds including terpenoids, phenylpropanoids, polyphenols, flavonoids, and sterols. However, there has been limited information available on the allelopathic properties and allelopathic substances of O. fragrans. We investigated the allelopathy and allelopathic substances of O. fragrans and Osmanthus heterophyllus (G.Don) P.S. Green, as well as Osmanthus × fortunei Carrière, which is the hybrid species between O. fragrans and O. heterophyllus. The leaf extracts of O. fragrans, O. heterophyllus, and O. × fortunei suppressed the growth of cress (Lepidium sativum L.), alfalfa (Medicago sativa L.), Lolium multiflorum Lam., and Vulpia myuros (L.) C.C.Gmel with the extract concentration dependently. The extract of the hybrid species O. × fortune was the most active among the extracts. The main allelopathic substances of O. × fortunei and O. fragrans were isolated and identified as (+)-pinoresinol and 10-acetoxyligustroside, respectively. (+)-Pinoresinol was also found in the fallen leaves of O. × fortunei. Both compounds showed an allelopathic activity on the growth of cress and L. multiflorum. On the other hand, several allelopathic substances including (+)-pinoresinol may be involved in the allelopathy of O. heterophyllus. O. fragrans, O. heterophyllus, and O. × fortunei are evergreen trees. but their senescent leaves fall and cover the soil under the trees. It is possible that those allelopathic substances are liberated through the decomposition process of the leaves into their rhizosphere soil, and that they accumulate in the soil and provide a competitive advantage to the species through the inhibition of the growth of the neighboring competing plants. Therefore, the leaves of these Osmanthus species are allelopathic and potentially useful for weed management options in some agriculture settings to reduce commercial herbicide dependency for the developing sustainable agriculture systems.

Zebrafish: A Model Deciphering the Impact of Flavonoids on Neurodegenerative Disorders

Over the past century, advances in biotechnology, biochemistry, and pharmacognosy have spotlighted flavonoids, polyphenolic secondary metabolites that have the ability to modulate many pathways involved in various biological mechanisms, including those involved in neuronal plasticity, learning, and memory. Moreover, flavonoids are known to impact the biological processes involved in developing neurodegenerative diseases, namely oxidative stress, neuroinflammation, and mitochondrial dysfunction. Thus, several flavonoids could be used as adjuvants to prevent and counteract neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Zebrafish is an interesting model organism that can offer new opportunities to study the beneficial effects of flavonoids on neurodegenerative diseases. Indeed, the high genome homology of 70% to humans, the brain organization largely similar to the human brain as well as the similar neuroanatomical and neurochemical processes, and the high neurogenic activity maintained in the adult brain makes zebrafish a valuable model for the study of human neurodegenerative diseases and deciphering the impact of flavonoids on those disorders.