Advances in the study of the function and mechanism of the action of flavonoids in plants under environmental stresses

The biochemical and molecular mechanisms of plants: a review on insect herbivory

Biochemical and molecular mechanisms have been essential mechanisms to reduce various insect attacks on plants. The biochemical methods are wide involving direct and indirect defenses. The defensive chemical substances are secreted effectively to the wound caused by the herbivores (insects and phytopathogens) on plants. Plants responded by producing VOCs which draw the natural enemies of the insects and phytopathogens. The progress observed in the cognition of the stimulus in plants and their potential to control the responses is characterized by the modification observed in molecular mechanisms which shifts our attention to the development of the endogenous resistance methods of preserving crops. The main objective of implementing a biotechnological mechanism in crop production is to employ durable and multimechanistic alternatives to insect pests via the stimulus the plant produces upon encountering the insect attack.

Effect of UV-B stress on olive (Olea europaea L.) pollen tubes: A study of callose plug deposition and male germ unit integrity

While UV-B radiation is beneficial to plant growth, it can also cause adverse effects. The pollen tube, a key component of plant reproduction with a tip growth mechanism, is an excellent cellular model for understanding how environmental stressors such as UV-B radiation affect plant cell growth. This research investigated the effect of UV-B on olive pollen both before and after germination. Pollen grains were hydrated and exposed to UV-B radiation for 1 h. Pollen tube germination was then evaluated 4 and 24 h after exposure. To study the effect of UV-B radiation on developing pollen tubes, pollen was germinated for 4 h prior to 1 h of UV-B exposure. Pollen tube growth was evaluated by assessing the distribution of cell wall components, the distance between callose plugs and nuclei, and the distance between the male germ unit and the pollen tube tip. We also examined the accumulation of callose synthase. The results showed that UV-B radiation significantly inhibited the growth of pollen tubes, thereby preventing successful fertilization. The effect of UV-B exposure on pollen tube growth was mainly due to the alteration of position of callose plugs and the level of callose synthase in the pollen tube, potentially affecting its growth. In addition, UV-B radiation affected the movement and integrity of the male germ unit, a critical element for successful fertilization. This research sheds light on how UV-B radiation affects the growth of pollen tubes and highlights the need for further research into the effects of UV-B radiation on plant cells and plant reproduction.

Integrative physiological and transcriptomic analysis provides insights on the molecular basis of ABA-enhanced drought tolerance in pear (Pyrus betulaefolia)

BACKGROUND

Drought stress could suppress the carbon assimilation and limit nutrient uptake of pear plants, thus affecting their growth and severely impacting the quality and yield of pear fruit. ABA is a stress hormone and is reported to alleviate drought stress in numerous plants. However, whether and how ABA functions in the drought responses of pear plants is yet explored.

RESULTS

Here, to address this gap, pear seedlings (Pyrus betulaefolia) were used and subjected to PEG-induced drought conditions with or without additional ABA in various doses. The results showed that while drought caused severe leaf water loss and damage, applying ABA at 50 µM and 100 µM dramatically amended the phenomenon, as indicated by the markedly increased relative water content, and notably decreased relative electrolyte leakage and malondialdehyde content. Based on the results of RNA sequencing and related physiological indices, it was found that drought grossly disrupted chlorophyll synthesis and photosynthesis. It induced the over-production of reactive oxygen species (ROS) and broke the ROS homeostasis, despite the pronounced increases in ABA biosynthesis/content and signaling, flavonoid synthesis, and antioxidant enzyme activities, as well as sugar metabolism. However, ABA applications significantly elevated the expressions of genes in chlorophyll synthesis and photosynthesis, partially boosting the SPAD and Fv/Fm values. In addition, ABA treatments further prominently accelerate the synthesis processes of ABA, flavonoids, and antioxidant enzymes by up-regulating the corresponding genes, resulting in endogenous ABA accumulation and enzymatic activity improvement, thereby expediting the ROS scavenging. Of course, the sugar metabolism pathway was also outstandingly enhanced to balance the growth and stress response of pear seedlings. Moreover, through WGCNA analysis, the core turquoise module associated with ABA-attenuated drought stress was identified, and a portion of key transcription factors (TFs) and some hub genes were characterized, particularly for ERF, WRKY, MYB, bHLH, NAC in TFs, and CSP, COR, and DHN in hub genes. Overall, our study reveals that exogenous ABA could help pear plants to efficiently scavenge drought-induced ROS by improving their photosynthesis capacity, ABA accumulation, sugar catabolism, enzymatic antioxidant system, etc. These results will provide a scientific basis and practical direction for utilizing ABA to mitigate the adverse effects of water starvation resulting from the persistent high temperature on pear plants in summer.

CONCLUSION

50 µM and 100 µM ABA application ameliorated the drought damage in pear seedlings, and the working routes are associated with reinforcement in the photosystem, ABA biosynthesis and signaling, flavonoid accumulation, and sugar metabolism, as well as enzymatic activities in ROS scavenging. The relevant regulatory network is complex, primarily concerned with ERF, WRKY, MYB, bHLH, and NAC TFs, with a focus on the potential target genes named CSP, COR, and DHN.

Waterlogging alone and combined with other abiotic stresses provides unique metabolic signatures at the plant-rhizosphere interface: A multi-omics perspective on root metabolome, root exudation and rhizomicrobiome

Despite the growing evidence on unique and unpredictable impact of stress combination over plants, waterlogging-combined stresses effects are still underexplored. Under those conditions, besides the impairment of plant aerial parts, the root system is particularly vulnerable, leading to consequences on plant survival. Here, we report on the short-term exposure of soil-grown Arabidopsis thaliana L. to waterlogging alone and combined with cold, heat, and salinity to inspect their antagonistic, additive or synergistic effects in the rhizosphere. To this aim, root metabolic changes, exudation profiles, and microbial diversity were investigated using a combination of metabolomics and metagenomics, and their interaction was analysed through multi-omics data integration. In roots, waterlogging strongly affected metabolism compared to other single stresses, causing a down-accumulation of targeted classes of compounds including, phenylpropanoids, sterols, terpenoids, and alkaloids. Additive and synergistic effects were reported in roots under waterlogging combined with heat and cold stresses, respectively. Regarding root exudates, flavonoids, terpenoids, and alkaloids were the main classes of compounds affected. Waterlogging caused a down-accumulation of all classes except for coumarins, and mixed trends were observed in waterlogging-combined stresses, with waterlogging-salinity stresses resulting in an ameliorating effect. Even though microbial communities' alpha- and beta-diversity remained stable, suggesting their resilience under short-term exposure, specific taxa modulation was recorded under each condition. Overall, these results contribute to understanding the hierarchical impact of waterlogging on root metabolism and exudation, influencing rhizosphere interactions. This multi-omics approach advances our understanding of plant stress responses and microbial dynamics, paving the way for future studies on adaptive mechanisms.

Integrated Physiological, Transcriptomic, and Metabolomic Analysis Reveals Mechanism Underlying the Serendipita indica-Enhanced Drought Tolerance in Tea Plants

Drought stress significantly impairs the output of tea plants and the quality of tea products. Although Serendipita indica has demonstrated the ability to enhance drought tolerance in host plants, its impact on tea plants (Camellia sinensis) experiencing drought stress is unknown. This study assessed the response of tea plants by inoculating S. indica under drought conditions. Phenotypic and physiological analyses demonstrated that S. indica mitigated drought damage in tea plants by regulating osmotic equilibrium and antioxidant enzyme activity. Metabolome analysis showed that S. indica promoted the accumulation of flavonoid metabolites, including naringin, (-)-epiafzelechin, naringenin chalcone, and dihydromyricetin, while inhibiting the content of amino acids and derivatives, such as homoarginine, L-arginine, N6-acetyl-L-lysine, and N-palmitoylglycine, during water deficit. The expression patterns of S. indica-stimulated genes were investigated using transcriptome analysis. S. indica-induced drought-responsive genes involved in osmotic regulation, antioxidant protection, transcription factors, and signaling were identified and recognized as possibly significant in S. indica-mediated drought tolerance in tea plants. Particularly, the flavonoid biosynthesis pathway was identified from the metabolomic and transcriptomic analysis using Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Moreover, flavonoid biosynthesis-related genes were identified. S. indica-inoculation significantly upregulated the expression of cinnamate 4-hydroxylase (C4H), chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin reductase (ANR), and leucoanthocyanidin reductase (LAR) genes compared to uninoculated plants subjected to water stress. Consequently, we concluded that S. indica inoculation primarily alleviates drought stress in tea plants by modulating the flavonoid biosynthesis pathway. These results will provide insights into the mechanisms of S. indica-enhanced drought tolerance in tea plants and establish a solid foundation for its application as a microbial agent in the management of drought in tea plants cultivation.

Green Pak Choi is better in suitable environment but the purple ones more resist to drought and shading

BACKGROUND

Studying how economic vegetable adapt to stressful environment is important not only for plant biology application but also to agronomy. In this study, we selected two commonly used genotypes of pak choi, i.e., larger green pak choi (Brassica rapa ssp. chinensis) and smaller purple pak choi (Brassica rapa var. chinensis, 'Rubi F1') to examine the divergent response of the two genotypes to drought and shading in the semi-arid region of Xinjiang. We compared the differences in biomass accumulation and plant morphological traits of the two pak choi in response to the interaction effects of drought (55-70% of field water capacity) and shading (24% reduction of canopy light radiation).

RESULTS

The results showed drought and shading significantly reduced the aboveground and belowground biomass of the two pak choi, with a particularly pronounced decrease in shoot biomass under the combined effect of shading + drought. The decline in shoot biomass was mostly resulted from decreasing in the number of leaves rather than in plant height and crown width in response to drought and shading. In terms of morphological traits, green pak choi sensitively responded to increased drought and shading, with aboveground biomass mostly determined by leaf number and root mass. In contrast, purple pak choi likely more resistant to the stressful environment, as its aboveground biomass was also influenced by plant height and crown width.

CONCLUSIONS

Hence it is important to consider not only the effects of drought but also the role of adequate light, which plays a key part in promoting the cultivation and growth of pak choi in stressful environments. The research and application of plant biology and agronomy in the region also need to consider the diversity of key economic plants to promote sustainability of vegetable farming in adapting to changing environmental stresses.

Spermidine Revives Aged Sorghum Seed Germination by Boosting Antioxidant Defense

Seed aging has adverse effects on agricultural production, mainly because seed vigor is inhibited. Spermidine can improve seed vitality and germination ability to a certain extent and is essential for plant growth and plant response to stress. This study explored how spermidine counteracted aging effects on sorghum seed germination through antioxidant metabolism regulation. Aged seeds showed decreased vigor due to heightened reactive oxygen species (ROS) and diminished antioxidants. Applying spermidine notably enhanced aged seeds' germination and vigor by boosting antioxidant enzyme activity and curbing ROS. Integrated transcriptomic, proteomic, and metabolomic analyses demonstrated that the majority of differentially expressed genes following exogenous spermidine treatment in aged sorghum seeds were significantly enriched in pathways related to glutathione metabolism, phenylpropanoid, and flavonoid biosynthesis, resulting in increased expression of genes encoding peroxidase, chalcone synthase, and glutathione s-transferase. Exogenous spermidine facilitated the synthesis of peroxidases and glutathione transferases. Analysis of flavonoid pathway intermediates showed a notable increase in antioxidant metabolites like isoquercitrin, underscoring their role in oxidative stress resistance. This multi-omics strategy underscores Spd's role in boosting aged seeds' antioxidants, highlighting the molecular basis of seed aging and Spd's rejuvenating impact.

Metabolomic analyses reveal that graphene oxide alleviates nicosulfuron toxicity in sweet corn

Nicosulfuron can repress the growth and quality of sweet corn (Zea mays), and graphene oxide has been used for sustainable agriculture. However, the underlying mechanism of the toxicity of nicosulfuron that is mediated in sweet corn remains elusive. To explore the potential mechanism of GO-mediated nicosulfuron toxicity in sweet corn in this study, we investigated the effects of graphene oxide on nicosulfuron stress in the sweet corn sister inbred lines of H01 and H20. Furthermore, we performed a metabolomics analysis for the H01 and H20 under different treatments. The results showed that nicosulfuron severely affected the rate of survival, physiological parameters, photosynthetic indicators, and chlorophyll fluorescence parameters of corn seedlings, whereas foliar spraying with graphene oxide promoted the rate of survival under nicosulfuron toxicity. The metabolomics analysis showed that 70 and 90 metabolites differentially accumulated in the H01 and H20 inbred lines under nicosulfuron treatment, respectively. Graphene oxide restored 59 metabolites in the H01 seedlings and 56 metabolites to normal levels in the H20 seedlings, thereby promoting the rate of survival of the sweet corn seedlings. Compared with nicosulfuron treatment alone, graphene oxide resulted in 108 and 66 differential metabolites in the H01 and H20 inbred lines, respectively. A correlation analysis revealed that metabolites, such as doronine and (R)-2-hydroxy-2-hydroxylase-1,4-benzoxazin-3(4-hydroxylase)-1, were significantly correlated with the rate of survival, photosynthetic parameters and chlorophyll fluorescence parameters. Furthermore, metabolites related to the detoxification of graphene oxide were enriched in the flavonoid metabolic pathways. These results collectively indicate that graphene oxide can be used as a regulator of corn growth and provide insights into their use to improve crops in areas that are contaminated with nicosulfuron.

Acetate prevents pistil dysfunction in rice under heat stress by inducing methyl jasmonate and quercetin synthesis

INTRODUCTION

Acetic acid (HAC) is a crucial signal molecule in plant stress responses; however, its role in conferring heat tolerance to rice remains unclear.

OBJECTIVES

This study aims to investigate the effect of HAC in protecting pistil function under heat stress and its potential role in facilitating pollen germination and tube growth via HAC-induced synthesis of methyl jasmonate (MeJA) and quercetin (QR).

METHODS

Physiological analysis, including pollen germination, pollen tube growth into the ovule, reactive oxygen species (ROS), as well as the levels of HAC, acetyl coenzyme A (acetyl-CoA), MeJA, and QR in the pistils of heat stress-treated early indica rice cultivars Zhongzao39 (ZZ39) and Zhongjiazao17 (ZJZ17), were conducted. RNA sequencing (RNA-seq) was performed to identify differentially expressed genes involved in this process. Effect of exogenous acetate (NaAC), MeJA, and QR on spikelet fertility were also investigated.

RESULTS

Compared with ZJZ17, severe inhibition of spikelet fertility, pollen germination, and pollen tube growth was observed in ZZ39, due to the ROS burst and an irregular distribution across the stigma, style, and ovule. RNA-seq and physiological data indicate that HAC may activate acetyl-CoA to enhance heat tolerance by inducing the synthesis of MeJA and QR. Exogenous NaAC enhanced spikelet fertility under heat stress, accompanied by elevated antioxidant enzyme activities, improved energy status, and increased levels of acetyl-CoA, MeJA, and QR in the pistils. Additionally, NaAC, MeJA, and QR, either alone or in combination, effectively augmented spikelet fertility under heat stress, while the combination of MeJA and QR inhibitors significantly reduced fertility.

CONCLUSION

Acetate activates acetyl-CoA to induce the synthesis of both MeJA and QR, thereby alleviating heat-induced pistil dysfunction by maintaining ROS homeostasis and enhancing the pollen germination, pollen tube growth and spikelet fertility. Our results offer a promising strategy to enhance the heat tolerance of crops.

Combined transcriptional and metabolomic analysis of flavonoids in the regulation of female flower bud differentiation in Juglans sigillata Dode

Juglans sigillata Dode is rich in flavonoids, but the low ratio of female to male flower buds limits the development of the J. sigillata industry. While the abundance of flavonoids in J. sigillata is known, whether flavonoids influence female flower bud differentiation has not been reported. In this study, we explored the regulatory mechanisms of gene expression and metabolite accumulation during female flower bud differentiation through integrated transcriptomic and metabolomic analyses. Our findings revealed that flavonoid biosynthesis is a key pathway influencing female flower bud differentiation, with metabolites primarily shifting towards the isoflavonoid, flavone, and flavonol branches. Structural genes such as chalcone synthase, dihydroflavonol 4-reductase, flavonol synthase, and flavonoid 3',5'-hydroxylase were identified as playing crucial regulatory roles. The expression of these genes promoted the accumulation of flavonoids, which in turn influenced female flower bud differentiation by modulating key regulatory genes including Suppressor of Overexpression of Constans1, Constans, Flowering Locus T, and APETALA1. Furthermore, transcription factors (TFs) highly expressed during the physiological differentiation of female flower buds, particularly M-type MADS, WRKY, and MYB, were positively correlated with flavonoid biosynthesis genes, indicating their significant role in the regulation of flavonoid production. These results offer valuable insights into the mechanisms of female flower bud differentiation in J. sigillata and highlight the regulatory role of flavonoids in plant bud differentiation.

Optimizing extrusion-based 3D bioprinting of plant cells with enhanced resolution and cell viability

3D bioprinting of plant cells has emerged as a promising technology for plant cell immobilization and related applications. Despite the numerous progress in mammalian cell printing, the bioprinting of plant cells is still in its infancy and needs further investigation. Here, we present a systematic study on optimizing the 3D bioprinting of plant cells, using carrots as an example, towards enhanced resolution and cell viability. We mainly investigated the effects of cell cluster forms and nozzle size on the rheological, extrusion, and printability properties of plant cell bioinks, as well as on the resultant cell viability and growth. We found that when the printing nozzle is larger than 85% of the cell clusters embedded in the bioink, smooth extrusion and good printability can be achieved together with considerable cell viability and long-term growth. Specifically, we optimized a bioink composited with suspension-cultured carrot cells, which exhibited better uniformity, smoother extrusion, and higher cell viability over 1 month culture compared to those with the regular callus or fragmented callus. This work provides a practical guideline for optimizing plant cell bioprinting from the bioink development to the printing outcome assessment. It highlights the importance of selecting a matched nozzle and cell cluster and might provide insights for a better understanding and exploitation of plant cell bioprinting.

Physiological and biochemical mechanisms of drought regulating the size and color of heartwood in Dalbergia odorifera

Drought has been found to affect the size and color of precious heartwood of Dalbergia odorifera, but the mechanism remains unclear. For this purpose, we performed the measurement of heartwood size, color and flavonoid content and composition in a 15-year-old mixed plantation of D. odorifera and Santalum album that had been subjected to two levels of rainfall exclusion and control treatments for 7 years, and carbon isotope labeling and anatomical observation in 2-year-old potted D. odorifera seedlings exposed to two levels of drought and control treatments. The field experiment showed that drought had significant effects on heartwood size and color of D. odorifera. More starch was depleted in the transition zone (TZ) in drought than in control. Drought significantly decreased the values of color parameters and increased the contents of total flavonoids, glycitein, fisetin, chrysin and claussequinone, and total flavonoids, glycitein, fisetin, chrysin and claussequinone were significantly negatively correlated with L* and b*. The pot experiment showed that during longitudinal transport of nonstructural carbohydrate (NSC), the dilution factor of 13C abundance in the inner bark sap in severe drought (SD) was twice as much as that in control. The inner bark thickness and transverse area of sieve tubes in SD were significantly lower than those in control. Our findings further confirm that drought promotes the heartwood formation of D. odorifera, and discuss interspecific variations in the response of heartwood formation to drought. Drought enhances the exchange transport of NSC between phloem and xylem by reducing the transverse area of sieve tubes, thus causing more NSC to be transported into xylem, and drought also promotes the depletion of starch in the TZ to produce more heartwood. Drought darkens the heartwood color by increasing the contents of total flavonoids, glycitein, fisetin, chrysin and claussequinone in heartwood. To our knowledge, this is the first study addressing the physiological and biochemical mechanism of drought regulating heartwood formation.

Integrated Transcriptomic and Metabolomic Analysis Revealed Regulatory Mechanisms on Flavonoids Biosynthesis in the Skin of Passion Fruit (Passiflora spp.)

Passion fruit is one of the most famous fruit crops in tropical and subtropical regions due to its high edible, medicinal, and ornamental value. Flavonoids, a class of plant secondary metabolites, have important health-related roles. In this study, a total of 151 flavonoid metabolites were identified, of which 25 key metabolites may be the main contributors to the purple phenotype. Using RNA sequencing, 11,180 differentially expressed genes (DEGs) were identified. Among these, 48 flavonoid biosynthesis genes (PAL, 4CL, C4H, CHS, CHI, F3H, DFR, ANS, and UFGT) and 123 transcription factors were identified. Furthermore, 12 distinct modules were identified through weighted gene coexpression network analysis, of which the brown module displays a robust positive correlation with numerous flavonoid metabolites. Overexpression of PeMYB114 significantly promoted flavonoids accumulation in tobacco leaves. Our study provided a key candidate gene for molecular breeding to improve color traits in passion fruit.

Characterization and metabolomic profiling of endophytic bacteria isolated from Moringa oleifera and Piper betel leaves

Endophytes are microorganisms residing in plant tissues without causing harm and their relevance in medicinal plants has grown due to their biomolecules used in pharmaceuticals. This study isolated two endophytic bacterial strains from the leaves of M. oleifera and P. betel collected from Junagadh Agricultural University. The isolates were characterized morphologically and physio-biochemically, confirming them as gram-positive or gram-negative rods and cocci. Identification using 16S rRNA gene sequencing identified isolates belonging to various genera, including Priestia aryabhattai and Kocuria rhizophila The SEM characterization of the five selected isolates revealed diverse morphological structures, including coccus and rod shapes, organized in various formations. Isolates varied in size, with N3 (Kocuria rhizophila) cocci and S5 (Priestia aryabhattai) rods. Metabolomic analysis using GC/MS and LC-MS revealed diverse metabolic profiles with key compounds like n-Hexadecanoic acid, Pyrrolo[1,2-a]pyrazine-1,4-dione, Dihydrocapsaicin, and β-Homoproline, highlighting the potential of these endophytic bacteria in agricultural applications due to their roles in membrane integrity, antioxidant properties, stress response, and antibacterial activity.

Preparation of monoclonal antibody against rhoifolin and its application in enzyme-linked immunosorbent assay of rhoifolin and diosmin

Both rhoifolin and diosmin belong to flavonoids, which are widely present in citrus. Diosmin is not only used in the medical field in the world, but also used as a dietary supplement in the United States. Rhoifolin has a similar structure to diosmin and also exhibits antioxidant and anti-inflammatory properties. In this study, an anti-rhoifolin monoclonal antibody was prepared and an indirect competitive enzyme-linked immunosorbent assay (icELISA) method was established. The half-maximal inhibitory concentration (IC50) of icELISA was determined to be 4.83 ng/mL, and the detection range was 0.97-33.87 ng/mL. The results of UPLC-MS/MS and icELISA generally demonstrate consistency. Moreover, by exploiting the cross-reactivity of the antibody, diosmin in tablets can be detected by icELISA. The results demonstrate that the developed method has good accuracy, reproducibility, and broad application prospects.

Pulsed Electric Field (PEF) Treatment Results in Growth Promotion, Main Flavonoids Extraction, and Phytochemical Profile Modulation of Scutellaria baicalensis Georgi Roots

This study aims to explore the effect of pulsed electric field (PEF) treatment as a method very likely to result in reversible electroporation of Scutellaria baicalensis Georgi underground organs, resulting in increased mass transfer and secondary metabolites leakage. PEF treatment with previously established empirically tailored parameters [E = 0.3 kV/cm (U = 3 kV, d = 10 cm), t = 50 µs, N = 33 f = 1 Hz] was applied 1-3 times to S. baicalensis roots submerged in four different Natural Deep Eutectic Solvents (NADES) media (1-choline chloride/xylose (1:2) + 30% water, 2-choline chloride/glucose (1:2) + 30% water, 3-choline chloride/ethylene glycol (1:2), and 4-tap water (EC = 0.7 mS/cm). Confocal microscopy was utilized to visualize the impact of PEF treatment on the root cells in situ. As a result of plant cell membrane permeabilization, an extract containing major active metabolites was successfully acquired in most media, achieving the best results using medium 1 and repeating the PEF treatment twice (baicalein Collapse

Key Words

• electroporation
• eutectic solvents
• flavonoids
• hydroponics

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MESH Headings

• Scutellaria baicalensis/chemistry
• Plant Roots/growth & development
• Plant Roots/chemistry
• Flavonoids/analysis
• Phytochemicals/chemistry
• Plant Extracts/pharmacology
• Plant Extracts/chemistry
• Electroporation/methods
• Electricity
• Flavanones/metabolism

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Grants

• UMO-2020/39/D/NZ9/01402 National Science Centre Poland

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Affiliation(s)

Kajetan Grzelka Department of Pharmaceutical Biology and Biotechnology, Division of Pharmaceutical Biology and Botany, Wrocław Medical University, 50-367 Wrocław, Poland; (K.G.); (A.M.)
Adam Matkowski Department of Pharmaceutical Biology and Biotechnology, Division of Pharmaceutical Biology and Botany, Wrocław Medical University, 50-367 Wrocław, Poland; (K.G.); (A.M.) Botanical Garden of Medicinal Plants, Wrocław Medical University, 50-367 Wrocław, Poland; (J.J.); (A.P.-B.)
Grzegorz Chodaczek Bioimaging Laboratory at Łukasiewicz Research Network—PORT Polish Center for Technology Development, 54-066 Wrocław, Poland;
Joanna Jaśpińska Botanical Garden of Medicinal Plants, Wrocław Medical University, 50-367 Wrocław, Poland; (J.J.); (A.P.-B.)
Anna Pawlikowska-Bartosz Botanical Garden of Medicinal Plants, Wrocław Medical University, 50-367 Wrocław, Poland; (J.J.); (A.P.-B.)
Wojciech Słupski Department of Pharmacology, Wrocław Medical University, 50-367 Wrocław, Poland;
Dorota Lechniak Department of Genetics and Animal Breeding, Poznań University of Life Sciences, Wołyńska 33, 60-637 Poznań, Poland;
Małgorzata Szumacher-Strabel Department of Animal Nutrition, Poznań University of Life Sciences, Poznań, Wołyńska 33, 60-637 Poznań, Poland; (M.S.-S.); (S.O.)
Segun Olorunlowu Department of Animal Nutrition, Poznań University of Life Sciences, Poznań, Wołyńska 33, 60-637 Poznań, Poland; (M.S.-S.); (S.O.)
Karolina Szulc Department of Animal Breeding and Product Quality Assessment, Poznań University of Life Sciences, Zlotniki, ul. Słoneczna 1, 62-002 Suchy Las, Poland;
Adam Cieślak Department of Animal Nutrition, Poznań University of Life Sciences, Poznań, Wołyńska 33, 60-637 Poznań, Poland; (M.S.-S.); (S.O.)
Sylwester Ślusarczyk Department of Pharmaceutical Biology and Biotechnology, Division of Pharmaceutical Biology and Botany, Wrocław Medical University, 50-367 Wrocław, Poland; (K.G.); (A.M.)

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Influence of Mikania micrantha Kunth Flavonoids on Composition of Soil Microbial Community

Mikania micrantha, one of the world's most destructive invasive species, is known for causing significant ecological and economic harm. While extensive research has focused on its growth characteristics, secondary metabolites, and control measures, its chemical interactions with the environment-particularly the role of flavonoids in shaping soil microbial communities-remain underexplored. In this study, we identified and quantified ten flavonoids from M. micrantha root exudates using UPLC-MS, including Hispidulin, Isorhamnetin, and Mikanin. To examine their impact, crude flavonoid extracts were applied to soil in potted experiments, which demonstrated that these compounds significantly increased soil fungal diversity and boosted the relative abundance of arbuscular mycorrhizal fungi (AMF). Furthermore, KEGG pathway analysis revealed that flavonoid addition elevated the copy numbers of genes involved in nitrogen cycling and metabolic functions, enhancing nutrient availability and microbial activity. Additionally, crude flavonoid extracts promoted the relative abundance of beneficial soil bacteria, such as Achromobacter, as well as AMF, both of which contribute to nutrient acquisition, plant growth, and soil health. These findings indicate that M. micrantha's flavonoids can alter soil microbial community composition, thereby creating a favorable environment that reinforces its competitive edge over native plants.

Changes in Growth and Metabolic Profile of Scutellaria baicalensis Georgi in Response to Sodium Chloride

Scutellaria baicalensis Georgi is a valuable medicinal plant of the Lamiaceae family. Its roots have been used in Traditional Chinese Medicine (under the name Huang-qin) since antiquity and are nowadays included in Chinese and European Pharmacopoeias. It is abundant in bioactive compounds which constitute up to 20% of dried root mass. These substances are lipophilic flavones with unsubstituted B-ring, baicalein, and wogonin and their respective glucuronides-baicalin and wogonoside being the most abundant. The content of these compounds is variable and the environmental factors causing this remain partially unknown. The role of these compounds in stress response is still being investigated and in our efforts to measure the effect of NaCl treatment on S. baicalensis growth and metabolic profile, we hope to contribute to this research. Short-term exposure to salt stress (50, 100, and 150 mM NaCl) resulted in a marked increase of baicalein from 1.55 mg to 2.55 mg/g DM (1.6-fold), baicalin from 8.2 mg to 14.7 mg (1.8-fold), wogonin from 4.9 to 6.8 (1.4-fold), and wogonoside from 3.3 to 6.8 mg/g DM (2-fold) in the roots. Conversely, in the aerial parts, the content of individual major flavonoids: carthamidine-7-O-glucuronide and scutellarein-7-O-glucuronide decreased the most by 10-50% from 18.6 mg to 11.3 mg/g (1.6-fold less) and from 6.5 mg to 3.4 mg/g DM (0.52-fold less), respectively. The amino acid profile was also altered with an increase in root concentrations of the following amino acids: arginine from 0.19 to 0.33 mg/g (1.7-fold), glutamate from 0.09 to 0.16 mg/g DM (1.6-fold), alanine from 0.009 to 0.06 mg/g (6.8-fold), proline from 0.011 to 0.029 (2.4-fold) and lysine from 0.016 to 0.063 mg/g (3.9-fold). Aspartate concentration decreased from 0.01 to 0.002 mg/g (4.8-fold less) at 150 mM NaCl. In the aerial parts, the concentration and variation in levels of specific amino acids differed among groups. For instance, the glutamate content exhibited a significant increase exclusively in the treatment group, rising from 0.031 to 0.034 mg/g, representing a 1.2-fold increase. Proline concentration showed a marked increase across all treated groups with the highest from 0.011 to 0.11 mg/g (10-fold). In conclusion, moderate salt stress was shown to increase S. baicalensis root biomass and flavonoid content which is rarely observed in a glycophyte species and provides a foundation for further studies on the mechanisms of osmotic stress adaptation on the specialized metabolism level.

Flavonoids and Other Phenolic Compounds for Physiological Roles, Plant Species Delimitation, and Medical Benefits: A Promising View

Flavonoids and other phenolic constituents are a large group of plant metabolites that have long attracted interest from researchers worldwide due to their functions in plant physiology, as well as their huge number of benefits for human health and well-being. This review attempts to reveal a promising view of the major physiological roles of flavonoids and other phenolic phytochemical molecules, e.g., protection agents against UV damage, pathogen defense agents, detoxifying agents, and agents promoting pollen fertility and successful pollination. Besides, the value of both flavonoids and other phenolic phytochemicals for plant species delimitation was also emphasized for the first time with the determination of their major physiological roles. Furthermore, their medical benefits for mankind were also highlighted in this current work.

Comparative Characterization of Three Homologous Glutathione Transferases from the Weed Lolium perenne

The comparative analysis of homologous enzymes is a valuable approach for elucidating enzymes' structure-function relationships. Glutathione transferases (GSTs, EC. 2.5.1.18) are crucial enzymes in maintaining the homeostatic stability of plant cells by performing various metabolic, regulatory, and detoxifying functions. They are promiscuous enzymes that catalyze a broad range of reactions that involve the nucleophilic attack of the activated thiolate of glutathione (GSH) to electrophilic compounds. In the present work, three highly homologous (96-98%) GSTs from ryegrass Lolium perenne (LpGSTs) were identified by in silico homology searches and their full-length cDNAs were isolated, cloned, and expressed in E. coli cells. The recombinant enzymes were purified by affinity chromatography and their substrate specificity and kinetic parameters were determined. LpGSTs belong to the tau class of the GST superfamily, and despite their high sequence homology, their substrate specificity displays remarkable differences. High catalytic activity was determined towards hydroxyperoxides and alkenals, suggesting a detoxification role towards oxidative stress metabolites. The prediction of the structure of the most active LpGST by molecular modeling allowed the identification of a non-conserved residue (Phe215) with key structural and functional roles. Site-saturation mutagenesis at position 215 and the characterization of eight mutant enzymes revealed that this site plays pleiotropic roles, affecting the affinity of the enzyme for the substrates, catalytic constant, and structural stability. The results of the work have improved our understanding of the GST family in L. perenne, a significant threat to agriculture, sustainable food production, and safety worldwide.

Integrated Metabolomic and Transcriptomic Analysis of Nitraria Berries Indicate the Role of Flavonoids in Adaptation to High Altitude

Background: Plants of Nitraria, belonging to the Zygophyllaceae family, are not only widely distributed at an altitude of about 1000 m but also at an altitude of about 3000 m, which is a rare phenomenon. However, little is known about the effect of altitude on the accumulation of metabolites in plants of Nitraria. Furthermore, the mechanism of the high-altitude adaptation of Nitraria has yet to be fully elucidated. Methods: In this study, metabolomics and transcriptomics were used to investigate the differential accumulation of metabolites of Nitraria berries and the regulatory mechanisms in different altitudes. Results: As a result, the biosynthesis of flavonoids is the most significant metabolic pathway in the process of adaptation to high altitude, and 5 Cyanidins, 1 Pelargonidin, 3 Petunidins, 1 Peonidin, and 4 Delphinidins are highly accumulated in high-altitude Nitraria. The results of transcriptomics showed that the structural genes C4H (2), F3H, 4CL (2), DFR (2), UFGT (2), and FLS (2) were highly expressed in high-altitude Nitraria. A network metabolism map of flavonoids was constructed, and the accumulation of differential metabolites and the expression of structural genes were analyzed for correlation. Conclusions: In summary, this study preliminarily offers a new understanding of metabolic differences and regulation mechanisms in plants of Nitraria from different altitudes.

Study on metabolic variation reveals metabolites important for flavor development and antioxidant property of Hainan Dayezhong black tea

To illustrate the development of chemical properties and characteristic flavor of Hainan Dayezhong black tea, the tea shoots under various manufacturing process were sampled and applied to targeted/widely-targeted metabolomic, transcriptomic, chemometric, and electronic sensory determinations. Totally, 2419 metabolites were identified in this study, of which 20 metabolites were selected as the biomarkers, mainly including amino acids, lipids, and pyrimidine derivatives. The metabolomic-transcriptomic integrated analysis indicated carbon fixation, flavonoid biosynthesis and amino acid metabolism were the major metabolic pathways over manufacturing process of Hainan Dayezhong black tea. The targeted metabolomic detection indicated the accumulations of free amino acids and reduction of total catechins, flavonol glycosides collectively contributed to the development of black tea taste; additionally, the antioxidative properties were decreasing along the production process. These results suggest that the tradeoff between bioactivity components and antioxidative capacity contribute to the characteristic flavor of Hainan Dayezhong black tea.

Streptomyces improves sugarcane drought tolerance by enhancing phenylalanine biosynthesis and optimizing the rhizosphere environment

Drought stress is a common hazard faced by sugarcane growth, and utilizing microorganisms to enhance plant tolerance to abiotic stress has become an important method for sustainable agricultural development. Several studies have demonstrated that Streptomyces chartreuses WZS021 improves sugarcane tolerance to drought stress. However, the molecular mechanisms underlying tolerance at the transcriptional and metabolomic levels remain unclear. We comprehensively evaluated the physiological and molecular mechanisms by which WZS021 enhances drought tolerance in sugarcane, by performing transcriptome sequencing and non-targeted metabolomics; and examining rhizosphere soil properties and plant tissue antioxidant capacity. WZS021 inoculation improved the rhizosphere nutritional environment (AP, ammonia, OM) of sugarcane and enhanced the antioxidant capacity of plant roots, stems, and leaves (POD, SOD, CAT). Comprehensive analyses of the transcriptome and metabolome revealed that WZS021 mainly affects plant drought tolerance through phenylalanine metabolism, plant hormone signal transduction, and flavonoid biosynthesis pathways. The drought tolerance signaling molecules mediated by WZS021 include petunidin, salicylic acid, α-Linoleic acid, auxin, geranylgeraniol and phenylalanine, as well as key genes related to plant hormone signaling transduction (YUCCA, amiE, AUX, CYPs, PAL, etc.). Interestingly, inoculation with WZS021 during regular watering induces a transcriptome-level response to biological stress in sugarcane plants. This study further elucidates a WZS021-dependent rhizosphere-mediated regulatory mechanism for improving sugarcane drought tolerance, providing a theoretical basis for increasing sugarcane production capacity.

The Influence of Sodium Humate on the Biosynthesis and Contents of Flavonoid Constituents in Lemons

Sodium humate (SH) is the sodium salt of humic acid. Our previous research has demonstrated that SH has the ability to enhance the levels of total flavonoids in various parts of lemons, including the leaves, peels, pulps, and seeds, thereby improving the quality of lemons. In the current study, the regulation effect of SH on the biosynthesis and content of lemon flavonoid compounds was examined using transcriptome sequencing technology and flavonoid metabolomic analysis. Following SH treatment, the transcriptome sequencing analysis revealed 320 differentially expressed genes (DEGs) between samples treated with SH and control (CK) samples, some of which were associated with the phenylalanine pathway by KEGG annotation analysis. The levels of seven flavonoid compounds identified in lemon peels were observed to increase, and eriocitrin and isoorientin were identified as differential metabolites (DMs, VIP > 1) using OPLS-DA analysis. The integrated analysis of transcriptomics and flavonoid metabolomics indicates that SH treatment induces alterations in gene expression and metabolite levels related to flavonoid synthesis. Specifically, SH influences flavonoid biosynthesis by modulating the activity of key enzymes in the phenylalanine pathway, including HCT (O-hydroxycinnamoyltransferase) and F5H (ferulate-5-hydroxylase).

Effects of alkaline salt stress on growth, physiological properties and medicinal components of clonal Glechoma longituba (Nakai) Kupr

BACKGROUND

Glechoma longituba, recognized as a medicinal plant, provides valuable pharmaceutical raw materials for treating various diseases. Saline-alkali stress may effectively enhance the medicinal quality of G. longituba by promoting the synthesis of secondary metabolites. To investigate the changes in the primary medicinal components of G. longituba under saline-alkali stress and improve the quality of medicinal materials, Na2CO3 was applied to induce short-term stress under different conditions and the biomass, physiologically active substances and primary medicinal components of G. longituba were measured in this study.

RESULTS

Under alkaline salt stress, the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) were elevated in G. longituba, accompanied by increased accumulation of proline (Pro) and malondialdehyde (MDA). Furthermore, analysis of the medicinal constituents revealed that G. longituba produced the highest levels of soluble sugars, flavonoids, ursolic acid, and oleanolic acid under 0.6% Na2CO3 stress for 48 h, 0.2% Na2CO3 stress for 72 h, 0.4% Na2CO3 stress for 12 h, and 0.4% Na2CO3 stress for 8 h, respectively.

CONCLUSIONS

Short-term Na2CO3 stress enhances the synthesis of medicinal components in G. longituba. By manipulating stress conditions, the production of various medicinal substances could be optimized. This approach may serve as a basis for the targeted cultivation of G. longituba, offering potential applications in the treatment of diverse diseases.

Multi-omics integrative analysis provided new insights into alkaline stress in alfalfa

Saline-alkali stress is one of the main abiotic stresses that limits plant growth. Salt stress has been widely studied, but alkaline salt degradation caused by NaHCO3 has rarely been investigated. In the present study, the alfalfa cultivar 'Zhongmu No. 1' was treated with 50 mM NaHCO3 (0, 4, 8, 12 and 24 h) to study the resulting enzyme activity and changes in mRNA, miRNA and metabolites in the roots. The results showed that the enzyme activity changed significantly after alkali stress treatment. The genomic analysis revealed 14,970 differentially expressed mRNAs (DEMs), 53 differentially expressed miRNAs (DEMis), and 463 differentially accumulated metabolites (DAMs). Combined analysis of DEMs and DEMis revealed that 21 DEMis negatively regulated 42 DEMs. In addition, when combined with Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of DEMs and DAMs, we found that phenylpropanoid biosynthesis, flavonoid biosynthesis, starch and sucrose metabolism and plant hormone signal transduction played important roles in the alkali stress response. The results of this study further elucidated the regulatory mechanism underlying the plant response to alkali stress and provided valuable information for the breeding of new saline-alkaline tolerance plant varieties.

Investigating the Impact of Flavonoids on Aspergillus flavus: Insights into Cell Wall Damage and Biofilms

Aspergillus flavus, a fungus known for producing aflatoxins, poses significant threats to agriculture and global health. Flavonoids, plant-derived compounds, inhibit A. flavus proliferation and mitigate aflatoxin production, although the precise molecular and physical mechanisms underlying these effects remain poorly understood. In this study, we investigated three flavonoids-apigenin, luteolin, and quercetin-applied to A. flavus NRRL 3357. We determined the following: (1) glycosylated luteolin led to a 10% reduction in maximum fungal growth capacity; (2) quercetin affected cell wall integrity by triggering extreme mycelial collapse, while apigenin and luteolin caused peeling of the outer layer of cell wall; (3) luteolin exhibited the highest antioxidant capacity in the environment compared to apigenin and quercetin; (4) osmotic stress assays did not reveal morphological defects; (5) flavonoids promoted cell adherence, a precursor for biofilm formation; and (6) RNA sequencing analysis revealed that flavonoids impact expression of putative cell wall and plasma membrane biosynthesis genes. Our findings suggest that the differential effects of quercetin, luteolin, and apigenin on membrane integrity and biofilm formation may be driven by their interactions with fungal cell walls. These insights may inform the development of novel antifungal additives or plant breeding strategies focusing on plant-derived compounds in crop protection.

SOS! Hydrogen Sulfide Enhances the Flavonoid Early Warning System in Rice Plants to Cope with Thiocyanate Pollution

The presence of thiocyanate (SCN-) in irrigation water has adverse effects on both plant growth and crop output. Hydrogen sulfide (H2S) is an important gaseous signaling molecule that can alleviate SCN- stress. Flavonoids are secondary compounds produced by plants and are ubiquitous in the plant kingdom. They play important roles in several physiological and biochemical processes. To investigate the effect of exogenous H2S on the growth of early rice plants under SCN- stress, we carried out a hydroponic experiment focusing on the interaction of exogenous H2S with flavonoids. In this study, a hydroponic experiment was performed to investigate the behavior of SCN- when subjected to varying effective doses (EC20: 24.0 mg/L; EC50: 96.0 mg/L; and EC75: 300.0 mg/L). The findings indicated that the relative growth rate (RGR) of the plants treated with H2S + SCN- was greater than that of the plants treated with SCN- alone. Higher amounts of flavonoids were detected in the shoots than in the roots, with more variability in the shoots. The early warning level results showed that most of the flavonoids were present at levels I and II, while quercetin was present at level IV. Genetic expression variation factor (GEVF) analyses revealed an increase in the quantity of "promoter genes" with increasing SCN- concentration in both rice tissues. Furthermore, administering external H2S while exposing rice tissues to SCN- resulted in a considerable decrease in the levels of reactive oxygen species. This study provides novel insights into the regulation of flavonoid levels in rice plants by exogenous H2S, facilitating enhanced resistance to SCN- stress and promoting sustainable agriculture.

Integrative proteome and metabolome unveil the central role of IAA alteration in axillary bud development following topping in tobacco

Axillary bud is an important aspect of plant morphology, contributing to the final tobacco yield. However, the mechanisms of axillary bud development in tobacco remain largely unknown. To investigate this aspect of tobacco biology, the metabolome and proteome of the axillary buds before and after topping were compared. A total of 569 metabolites were differentially abundant before and 1, 3, and 5 days after topping. KEGG analyses further revealed that the axillary bud was characterized by a striking enrichment of metabolites involved in flavonoid metabolism, suggesting a strong flavonoid biosynthesis activity in the tobacco axillary bud after topping. Additionally, 9035 differentially expressed proteins (DEPs) were identified before and 1, 3, and 5 days after topping. Subsequent GO and KEGG analyses revealed that the DEPs in the axillary bud were enriched in oxidative stress, hormone signal transduction, MAPK signaling pathway, and starch and sucrose metabolism. The integrated proteome and metabolome analysis revealed that the indole-3-acetic acid (IAA) alteration in buds control dormancy release and sustained growth of axillary bud by regulating proteins involved in carbohydrate metabolism, amino acid metabolism, and lipid metabolism. Notably, the proteins related to reactive oxygen species (ROS) scavenging and flavonoid biosynthesis were strongly negatively correlated with IAA content. These findings shed light on a critical role of IAA alteration in regulating axillary bud outgrowth, and implied a potential crosstalk among IAA alteration, ROS homeostasis, and flavonoid biosynthesis in tobacco axillary bud under topping stress, which could improve our understanding of the IAA alteration in axillary bud as an important regulator of axillary bud development.

The mechanism by which oriented polypropylene packaging alleviates postharvest 'Black Spot' in radish root (Raphanus sativus)

INTRODUCTION

The postharvest physiological disorder known as 'black spot' in radish roots (Raphanus sativus) poses a significant challenge to quality maintenance during storage, particularly under summer conditions. The cause of this disorder, however, is poorly understood.

OBJECTIVES

Characterize the underlying causes of 'black spot' disorder in radish roots and identify strategies to delay its onset.

METHODS

Radish roots were placed in either polyvinyl chloride (PVC) or oriented polypropylene (OPP) packaging and stored for 4 days at 30 °C. Appearance and physiological parameters were assessed and transcriptomic and metabolomic analyses were conducted to identify the key molecular and biochemical factors contributing to the disorder and strategies for delaying its onset and development.

RESULTS

OPP packaging effectively delayed the onset of 'black spot' in radishes, potentially due to changes in phenolic and lipid metabolism. Regarding phenolic metabolism, POD and PPO activity decreased, RsCCR and RsPOD expression was downregulated, genes involved in phenols and flavonoids synthesis were upregulated and their content increased, preventing the oxidative browning of phenols and generally enhancing stress tolerance. Regarding lipid metabolism, the level of alpha-linolenic acid increased, and genes regulating cutin and wax synthesis were upregulated. Notably, high flavonoid and low ROS levels collectively inhibited RsPLA2G expression, which reduced the production of arachidonic acid, pro-inflammatory compounds (LTA4 and PGG2), and ROS, alleviating the inflammatory response and oxidative stress in radish epidermal tissues.

CONCLUSION

PVC packaging enhanced the postharvest onset of 'black spot' in radishes, while OPP packaging delayed both its onset and development. Our study provides insights into the response of radishes to different packaging materials during storage, and the causes and host responses that either enhance or delay 'black spot' disorder onset. Further studies will be conducted to confirm the molecular and biochemical processes responsible for the onset and development of 'black spot' in radishes.

Integrated metabolomic and transcriptomic analysis reveals the regulatory mechanisms of flavonoid and alkaloid biosynthesis in the new and old leaves of Murraya tetramera Huang

BACKGROUND

Murraya tetramera Huang is a traditional Chinese woody medicine. Its leaves contain flavonoids, alkaloids, and other active compounds, which have anti-inflammatory and analgesic effects, as well as hypoglycemic and lipid-lowering effects, and anti-tumor effects. There are significant differences in the content of flavonoids and alkaloids in leaves during different growth cycles, but the synthesis mechanism is still unclear.

RESULTS

In April 2021, new leaves (one month old) and old leaves (one and a half years old) of M. tetramera were used as experimental materials to systematically analyze the changes in differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) with transcriptomics and metabolomics technology. This was done to identify the signaling pathways of flavonoid and alkaloid synthesis. The results showed that the contents of total alkaloids and flavonoids in old leaves were significantly higher than those in new leaves. Thirteen flavonoid compounds, three isoflavone compounds, and nineteen alkaloid compounds were identified, and 125 and 48 DEGs related to flavonoid and alkaloid synthesis were found, respectively. By constructing the KEGG (Kyoto Encyclopedia of Genes and Genomes) network of DEGs and DAMs, it was shown that the molecular mechanism of flavonoid biosynthesis in M. tetramera mainly focuses on the "flavonoid biosynthetic pathway" and the "flavonoid and flavonol biosynthetic pathway". Among them, p-Coumaryl alcohol, Sinapyl alcohol, Phloretin, and Isoquercitrin were significantly accumulated in old leaves, the up-regulated expression of CCR (cinnamoyl-CoA reductase) might promote the accumulation of p-Coumaryl alcohol, upregulation of F5H (ferulate-5-hydroxylase) might promote Sinapyl alcohol accumulation. Alkaloids, including indole alkaloids, pyridine alkaloids, imidazole alkaloids, and quinoline alkaloids, were significantly accumulated in old leaves, and a total of 29 genes were associated with these substances.

CONCLUSIONS

These data are helpful to better understand the biosynthesis of flavonoids and alkaloids in M. tetramera and provide a scientific basis for the development of medicinal components in M. tetramera.

Integrated Transcriptomic and Metabolomic Analysis Reveals the Molecular Regulatory Mechanism of Flavonoid Biosynthesis in Maize Roots under Lead Stress

Flavonoids are secondary metabolites that play important roles in the resistance of plants to abiotic stress. Despite the widely reported adverse effects of lead (Pb) contamination on maize, the effects of Pb on the biosynthetic processes of flavonoids in maize roots are still unknown. In the present work, we employed a combination of multi-omics and conventional assay methods to investigate the effects of two concentrations of Pb (40 and 250 mg/kg) on flavonoid biosynthesis in maize roots and the associated molecular regulatory mechanisms. Analysis using conventional assays revealed that 40 and 250 mg/kg Pb exposure increased the lead content of maize root to 0.67 ± 0.18 mg/kg and 3.09 ± 0.02 mg/kg, respectively, but they did not result in significant changes in maize root length. The multi-omics results suggested that exposure to 40 mg/kg of Pb caused differential expression of 33 genes and 34 metabolites related to flavonoids in the maize root system, while 250 mg/kg of Pb caused differential expression of 34 genes and 31 metabolites. Not only did these differentially expressed genes and metabolites participate in transferase activity, anthocyanin-containing compound biosynthetic processes, metal ion binding, hydroxyl group binding, cinnamoyl transferase activity, hydroxycinnamoyl transferase activity, and flavanone 4-reductase activity but they were also significantly enriched in the flavonoid, isoflavonoid, flavone, and flavonol biosynthesis pathways. These results show that Pb is involved in the regulation of maize root growth by interfering with the biosynthesis of flavonoids in the maize root system. The results of this study will enable the elucidation of the mechanisms of the effects of lead on maize root systems.

Antiplatelet Effects of Flavonoid Aglycones Are Mediated by Activation of Cyclic Nucleotide-Dependent Protein Kinases

Flavonoid aglycones are secondary plant metabolites that exhibit a broad spectrum of pharmacological activities, including anti-inflammatory, antioxidant, anticancer, and antiplatelet effects. However, the precise molecular mechanisms underlying their inhibitory effect on platelet activation remain poorly understood. In this study, we applied flow cytometry to analyze the effects of six flavonoid aglycones (luteolin, myricetin, quercetin, eriodictyol, kaempferol, and apigenin) on platelet activation, phosphatidylserine externalization, formation of reactive oxygen species, and intracellular esterase activity. We found that these compounds significantly inhibit thrombin-induced platelet activation and decrease formation of reactive oxygen species in activated platelets. The tested aglycones did not affect platelet viability, apoptosis induction, or procoagulant platelet formation. Notably, luteolin, myricetin, quercetin, and apigenin increased thrombin-induced thromboxane synthase activity, which was analyzed by a spectrofluorimetric method. Our results obtained from Western blot analysis and liquid chromatography-tandem mass spectrometry demonstrated that the antiplatelet properties of the studied phytochemicals are mediated by activation of cyclic nucleotide-dependent signaling pathways. Specifically, we established by using Förster resonance energy transfer that the molecular mechanisms are, at least partly, associated with the inhibition of phosphodiesterases 2 and/or 5. These findings underscore the therapeutic potential of flavonoid aglycones for clinical application as antiplatelet agents.

Reduction of flavonoid content in honeysuckle via Erysiphe lonicerae-mediated inhibition of three essential genes in flavonoid biosynthesis pathways

Honeysuckle, valued for its wide-ranging uses in medicine, cuisine, and aesthetics, faces a significant challenge in cultivation due to powdery mildew, primarily caused by the Erysiphe lonicerae pathogen. The interaction between honeysuckle and E. lonicerae, especially concerning disease progression, remains insufficiently understood. Our study, conducted in three different locations, found that honeysuckle naturally infected with E. lonicerae showed notable decreases in total flavonoid content, with reductions of 34.7%, 53.5%, and 53.8% observed in each respective site. Controlled experiments supported these findings, indicating that artificial inoculation with E. lonicerae led to a 20.9% reduction in flavonoid levels over 21 days, worsening to a 54.8% decrease by day 42. Additionally, there was a significant drop in the plant's total antioxidant capacity, reaching an 81.7% reduction 56 days after inoculation. Metabolomic analysis also revealed substantial reductions in essential medicinal components such as chlorogenic acid, luteolin, quercetin, isoquercetin, and rutin. Investigating gene expression revealed a marked decrease in the relative expression of the LjPAL1 gene, starting as early as day 7 post-inoculation and falling to a minimal level (fold change = 0.29) by day 35. This trend was mirrored by a consistent reduction in phenylalanine ammonia-lyase activity in honeysuckle through the entire process, which decreased by 72.3% by day 56. Further analysis showed significant and sustained repression of downstream genes LjFNHO1 and LjFNGT1, closely linked to LjPAL1. We identified the mechanism by which E. lonicerae inhibits this pathway and suggest that E. lonicerae may strategically weaken the honeysuckle's disease resistance by targeting key biosynthetic pathways, thereby facilitating further pathogen invasion. Based on our findings, we recommend two primary strategies: first, monitoring medicinal constituent levels in honeysuckle from E. lonicerae-affected areas to ensure its therapeutic effectiveness; and second, emphasizing early prevention and control measures against honeysuckle powdery mildew due to the persistent decline in crucial active compounds.

Integrated Full-Length Transcriptomics and Metabolomics Reveal Glycosyltransferase Involved in the Biosynthesis of Flavonol Glycosides in Laportea bulbifera

Many species of the Urticaceae family are important cultivated fiber plants that are known for their economic and industrial values. However, their secondary metabolite profiles and associated biosynthetic mechanisms have not been well-studied. Using Laportea bulbifera as a model, we conducted widely targeted metabolomics, which revealed 523 secondary metabolites, including a unique accumulation of flavonol glycosides in bulblet. Through full-length transcriptomic and RNA-seq analyses, the related genes in the flavonoid biosynthesis pathway were identified. Finally, weighted gene correlation network analysis and functional characterization revealed four LbUGTs, including LbUGT78AE1, LbUGT72CT1, LbUGT71BX1, and LbUGT71BX2, can catalyze the glycosylation of flavonol aglycones (kaempferol, myricetin, gossypetin, and quercetagetin) using UDP-Gal and UDP-Glu as the sugar donors. LbUGT78AE1 and LbUGT72CT1 showed substrate promiscuity, whereas LbUGT71BX1 and LbUGT71BX2 exhibited different substrate and sugar donor selectivity. These results provide a genetic resource for studying Laportea in the Urticaceae family, as well as key enzymes responsible for the metabolism of valuable flavonoid glycosides.

Unveiling characteristic metabolic accumulation over enzymatic-catalyzed process of Tieguanyin oolong tea manufacturing by DESI-MSI and multiple-omics

To achieve an integrative understanding of the spatial distribution and chronological flavoring compounds accumulation, desorption-electrospray-ionization coupled mass-spectrometry-imaging (DESI-MSI) and multi-omics techniques were performed on the leaf samples collected from the enzymatic-catalyzed-process (ECP) stage of Tieguanyin oolong tea manufacturing. The result of DESI-MSI visualization indicated transform or re-distribution of catechins, flavonols and amino acids were on-going attributing to the multi-stress over ECP stage. Out of identified 2621 non-volatiles and 45,771 transcripts, 43 non-volatiles and 12 co-expressed pathways were screened out as biomarkers and key cascades in response to adverse conditions. The targeted metabolic analysis on the characteristic flavoring compounds showed that the accumulations of free amino acids were enhanced, while catechins, flavonol glycosides, and alkaloids exhibited dynamic changes. This result suggests withering and turning-over process are compatible and collectively regulate the metabolic accumulation and development of flavoring metabolites, facilitating to the development of characteristic quality of Tieguanyin tea.

Alfalfa Responses to Intensive Soil Compaction: Effects on Plant and Root Growth, Phytohormones and Internal Gene Expression

The perennial legume alfalfa (Medicago sativa L.) is of high value in providing cheap and high-nutritive forages. Due to a lack of tillage during the production period, the soil in which alfalfa grows prunes to become compacted through highly mechanized agriculture. Compaction deteriorates the soil's structure and fertility, leading to compromised alfalfa development and productivity. However, the way alfalfa responses to different levels of soil compaction and the underlying molecular mechanism are still unclear. In this study, we systematically evaluated the effects of gradient compacted soil on the growth of different cultivars of alfalfa, especially the root system architecture, phytohormones and internal gene expression profile alterations. The results showed that alfalfa growth was facilitated by moderate soil compaction, but drastically inhibited when compaction was intensified. The inhibition effect was universal across different cultivars, but with different severity. Transcriptomic and physiological studies revealed that the expression of a set of genes regulating the biosynthesis of lignin and flavonoids was significantly repressed in compaction treated alfalfa roots, and this might have resulted in a modified secondary cell wall and xylem vessel formation. Phytohormones, like ABA, are supposed to play pivotal roles in the regulation of the overall responses. These findings provide directions for the improvement of field soil management in alfalfa production and the molecular breeding of alfalfa germplasm with better soil compaction resilience.

Integrative multi-omics analysis reveals the crucial biological pathways involved in the adaptive response to NaCl stress in peanut seedlings

Plant growth is restricted by salt stress, which is a significant abiotic factor, particularly during the seedling stage. The aim of this study was to investigate the mechanisms underlying peanut adaptation to salt stress by transcriptomic and metabolomic analysis during the seedling stage. In this study, phenotypic variations of FH23 and NH5, two peanut varieties with contrasting tolerance to salt, changed obviously, with the strongest differences observed at 24 h. FH23 leaves wilted and the membrane system was seriously damaged. A total of 1470 metabolites were identified, with flavonoids being the most common (21.22%). Multi-omics analyses demonstrated that flavonoid biosynthesis (ko00941), isoflavones biosynthesis (ko00943), and plant hormone signal transduction (ko04075) were key metabolic pathways. The comparison of metabolites in isoflavone biosynthesis pathways of peanut varieties with different salt tolerant levels demonstrated that the accumulation of naringenin and formononetin may be the key metabolite leading to their different tolerance. Using our transcriptomic data, we identified three possible reasons for the difference in salt tolerance between the two varieties: (1) differential expression of LOC112715558 (HIDH) and LOC112709716 (HCT), (2) differential expression of LOC112719763 (PYR/PYL) and LOC112764051 (ABF) in the abscisic acid (ABA) signal transduction pathway, then (3) differential expression of genes encoding JAZ proteins (LOC112696383 and LOC112790545). Key metabolites and candidate genes related to improving the salt tolerance in peanuts were screened to promote the study of the responses of peanuts to NaCl stress and guide their genetic improvement.

Untargeted Metabolomics Based on UPLC-Q-Exactive-Orbitrap-MS/MS Revealed the Differences and Correlations between Different Parts of the Root of Paeonia lactiflora Pall

BACKGROUND

Paeonia lactiflora Pall. (PLP) is a plant with excellent ornamental and therapeutic value that can be utilized in traditional Chinese medicine as Paeoniae Radix Alba (PRA) and Paeoniae Radix Rubra (PRR). PRA must undergo the "peeling" process, which involves removing the cork and a portion of the phloem. PLP's biological function is strongly linked to its secondary metabolites, and the distribution of metabolites in different regions of the PLP rhizome causes changes in efficacy when PLP is processed into various therapeutic compounds.

METHODS

The metabolites of the cork (cor), phloem (phl), and xylem (xyl) were examined in the roots of PLP using a metabolomics approach based on UPLC-Q-Exactive-Orbitrap-MS/MS (UPLC-MS/MS), and the differential metabolites were evaluated using multivariate analysis.

RESULTS

Significant changes were observed among the cor, phl, and xyl samples. In both positive and negative ion modes, a total of 15,429 peaks were detected and 7366 metabolites were identified. A total of 525 cor-phl differential metabolites, 452 cor-xyl differential metabolites, and 328 phl-xyl differential metabolites were evaluated. Flavonoids, monoterpene glycosides, fatty acids, sugar derivatives, and carbohydrates were among the top 50 dissimilar chemicals. The key divergent metabolic pathways include linoleic acid metabolism, galactose metabolism, ABC transporters, arginine biosynthesis, and flavonoid biosynthesis.

CONCLUSION

The cor, phl, and xyl of PLP roots exhibit significantly different metabolite types and metabolic pathways; therefore, "peeling" may impact the pharmaceutical effect of PLP. This study represents the first metabolomics analysis of the PLP rhizome, laying the groundwork for the isolation and identification of PLP pharmacological activity, as well as the quality evaluation and efficacy exploration of PLP.

Data-Driven Characterization of Metabolome Reprogramming during Early Development of Sorghum Seedlings

Specialized metabolites are produced via discrete metabolic pathways. These small molecules play significant roles in plant growth and development, as well as defense against environmental stresses. These include damping off or seedling blight at a post-emergence stage. Targeted metabolomics was followed to gain insights into metabolome changes characteristic of different developmental stages of sorghum seedlings. Metabolites were extracted from leaves at seven time points post-germination and analyzed using ultra-high performance liquid chromatography coupled to mass spectrometry. Multivariate statistical analysis combined with chemometric tools, such as principal component analysis, hierarchical clustering analysis, and orthogonal partial least squares-discriminant analysis, were applied for data exploration and to reduce data dimensionality as well as for the selection of potential discriminant biomarkers. Changes in metabolome patterns of the seedlings were analyzed in the early, middle, and late stages of growth (7, 14, and 29 days post-germination). The metabolite classes were amino acids, organic acids, lipids, cyanogenic glycosides, hormones, hydroxycinnamic acid derivatives, and flavonoids, with the latter representing the largest class of metabolites. In general, the metabolite content showed an increase with the progression of the plant growth stages. Most of the differential metabolites were derived from tryptophan and phenylalanine, which contribute to innate immune defenses as well as growth. Quantitative analysis identified a correlation of apigenin flavone derivatives with growth stage. Data-driven investigations of these metabolomes provided new insights into the developmental dynamics that occur in seedlings to limit post-germination mortality.

Chromosome-level genome assembly and demographic history of Euryodendron excelsum in monotypic genus endemic to China

Euryodendron excelsum is in a monotypic genus Euryodendron, endemic to China. It has intermediate morphisms in the Pentaphylacaceae or Theaceae families, which make it distinct. Due to anthropogenic disturbance, E. excelsum is currently found in very restricted and fragmented areas with extremely small populations. Although much research and effort has been applied towards its conservation, its long-term survival mechanisms and evolutionary history remain elusive, especially from a genomic aspect. Therefore, using a combination of long/short whole genome sequencing, RNA sequencing reads, and Hi-C data, we assembled and annotated a high-quality genome for E. excelsum. The genome assembly of E. excelsum comprised 1,059,895,887 bp with 99.66% anchored into 23 pseudo-chromosomes and a 99.0% BUSCO completeness. Comparative genomic analysis revealed the expansion of terpenoid and flavonoid secondary metabolite genes, and displayed a tandem and/or proximal duplication framework of these genes. E. excelsum also displayed genes associated with growth, development, and defence adaptation from whole genome duplication. Demographic analysis indicated that its fluctuations in population size and its recent population decline were related to cold climate changes. The E. excelsum genome assembly provides a highly valuable resource for evolutionary and ecological research in the future, aiding its conservation, management, and restoration.

An integrated metabolomic and transcriptomic analysis reveals the dynamic changes of key metabolites and flavor formation over Tieguanyin oolong tea production

To interpret the formation characteristic flavor during oolong tea manufacturing process, the dynamic changes of key flavor components in samples from various processing steps of Tieguanyin oolong tea production were investigated using widely-targeted metabolomic and the transcriptomic approaches. As a result, a total of 1078 metabolites were determined, of which 62 compounds were identified as biomarkers significantly changed over the manufacturing process. Quantitative determination of the total 50,343 transcripts showed 7480 of them were co-expressed different genes. Glutamic acid served as a critical metabolism hub and a signaling molecule for diverse stress responses. Additionally, the targeted quantification results showed that the contents of catechins and xanthine alkaloids in dried tea were dramatically decreased by 20.19% and 7.15% respectively than those in fresh leaves, which potentially contributed to the alleviation of astringent or bitter palates, promoting the characteristic mellow and rich flavor of Tieguanyin oolong tea.

Metabolomic Reconfiguration in Primed Barley (Hordeum vulgare) Plants in Response to Pyrenophora teres f. teres Infection

Necrotrophic fungi affect a wide range of plants and cause significant crop losses. For the activation of multi-layered innate immune defences, plants can be primed or pre-conditioned to rapidly and more efficiently counteract this pathogen. Untargeted and targeted metabolomics analyses were applied to elucidate the biochemical processes involved in the response of 3,5-dichloroanthranilic acid (3,5-DCAA) primed barley plants to Pyrenophora teres f. teres (Ptt). A susceptible barley cultivar ('Hessekwa') at the third leaf growth stage was treated with 3,5-DCAA 24 h prior to infection using a Ptt conidia suspension. The infection was monitored over 2, 4, and 6 days post-inoculation. For untargeted studies, ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-MS) was used to analyse methanolic plant extracts. Acquired data were processed to generate the data matrices utilised in chemometric modelling and multi-dimensional data mining. For targeted studies, selected metabolites from the amino acids, phenolic acids, and alkaloids classes were quantified using multiple reaction monitoring (MRM) mass spectrometry. 3,5-DCAA was effective as a priming agent in delaying the onset and intensity of symptoms but could not prevent the progression of the disease. Unsupervised learning methods revealed clear differences between the sample extracts from the control plants and the infected plants. Both orthogonal projection to latent structure-discriminant analysis (OPLS-DA) and 'shared and unique structures' (SUS) plots allowed for the extraction of potential markers of the primed and naïve plant responses to Ptt. These include classes of organic acids, fatty acids, amino acids, phenolic acids, and derivatives and flavonoids. Among these, 5-oxo-proline and citric acid were notable as priming response-related metabolites. Metabolites from the tricarboxylic acid pathway were only discriminant in the primed plant infected with Ptt. Furthermore, the quantification of targeted metabolites revealed that hydroxycinnamic acids were significantly more prominent in the primed infected plants, especially at 2 d.p.i. Our research advances efforts to better understand regulated and reprogrammed metabolic responses that constitute defence priming in barley against Ptt.

From Nature to Lab: A Review of Secondary Metabolite Biosynthetic Pathways, Environmental Influences, and In Vitro Approaches

Secondary metabolites are gaining an increasing importance in various industries, such as pharmaceuticals, dyes, and food, as is the need for reliable and efficient methods of procuring these compounds. To develop sustainable and cost-effective approaches, a comprehensive understanding of the biosynthetic pathways and the factors influencing secondary metabolite production is essential. These compounds are a unique type of natural product which recognizes the oxidative damage caused by stresses, thereby activating the defence mechanism in plants. Various methods have been developed to enhance the production of secondary metabolites in plants. The elicitor-induced in vitro culture technique is considered an efficient tool for studying and improving the production of secondary metabolites in plants. In the present review, we have documented various biosynthetic pathways and the role of secondary metabolites under diverse environmental stresses. Furthermore, a practical strategy for obtaining consistent and abundant secondary metabolite production via various elicitation agents used in culturing techniques is also mentioned. By elucidating the intricate interplay of regulatory factors, this review paves the way for future advancements in sustainable and efficient production methods for high-value secondary metabolites.