Fulvic acid ameliorates drought stress-induced damage in tea plants by regulating the ascorbate metabolism and flavonoids biosynthesis

Metabolome reveals high nitrogen supply decreases the antioxidant capacity of blue honeysuckle (Lonicera caerulea L.) by regulating flavonoids

The objectives of this research were to analyze the effects of varying nitrogen application rates on fruit quality and antioxidant properties of blue honeysuckle through widely targeted metabolomics analysis. High nitrogen application resulted in a reduction in fruit size and soluble solid content, along with significant decreases in the levels of total anthocyanins, phenolic compounds, flavonoids, and antioxidant indices. Under low nitrogen, key flavonoids in fruit namely Kaempferol-7-O-glucoside, Morin 3-alpha-L-lyxopyranoside, and Quercetin-3-O-xyloside (Reynoutrin) showed the high peak areas, with SOD, POD, and CAT activities at 1742.19, 45,525.65, and 1065.13 U/g, but decreased under high nitrogen. The molecular docking analysis revealed affinity values of -5.39, -2.72, -4.37, -3.98, -4.04, -4.18, -2.51, -2.31, and - 4.08 kcal/mol for SOD, POD, and CAT. These three flavonoids play a crucial role in the antioxidant defense system by targeting different enzymes, and their reduced concentrations under high nitrogen conditions may impair the fruit's antioxidant capacity.

Application of proteomics in investigating the responses of plant to abiotic stresses

MAIN CONCLUSION

This review summarizes the application of proteomic techniques in investigating the responses of plant to abiotic stresses. In the natural environment, the plants are exposed to a diverse range of adverse abiotic factors that significantly impact their growth and development. The plants have evolved intricate stress response mechanisms at the genetic, protein, metabolic, and phenotypic levels to mitigate damage caused by unfavorable conditions. Proteomics serves as an effective tool for studying protein changes in plants and provides valuable insights into the physiological mechanisms underlying plant stress resistance. Several proteins involved in abiotic stress responses have been identified in plants, including transcription factors, protein kinases, ATP synthases, heat shock proteins, redox proteins, and enzymes in secondary metabolite pathways. Medicinal plants are a unique category of crops capable of synthesizing secondary metabolites, which play a crucial role in resisting abiotic stress and exhibit changes in content under stress conditions. In this review, we present an overview of proteomic tools employed for investigating the responses of plants to abiotic stresses and summarize alterations observed at the protein level under various abiotic stresses such as signal transduction, oxidative damage, carbohydrate and energy metabolism, protein and amino acid metabolism, cellular homeostasis, and enzyme involvement in secondary metabolism. This work aims to facilitate the application of proteomics techniques in plants research while enhancing our understanding of the response mechanisms exhibited by these plants towards abiotic stresses.

Multidimensional evaluation of quality differences for Dendrobium officinale stems grown under different cultivation environments based on widely targeted metabolomics, network pharmacology, molecular docking, and cell experiments

Introduction

Dendrobium officinale is an endangered perennial epiphytic herbaceous plant. In the Chinese Pharmacopoeia, the dried stems of D. officinale are used medicinally and are commonly utilized as a medicinal and food homologous product. Notable variations in the quality of D. officinale stems are observed across different cultivation environments; however, the underlying mechanisms remain unclear.

Methods

Metabolites in D. officinale stems grown in stone epiphytic, tree epiphytic, and greenhouse environments were identified using UPLC-MS/MS-based widely targeted metabolomics. Differential metabolites from stems grown in different cultivation environments were selected for studies on quality differences. Network pharmacology was employed to investigate the core targets of these differential metabolites, and molecular docking validation was conducted with these metabolites to identify quality markers. Finally, a combination of network pharmacology and in vitro experimental results was used to explore the reasons behind the differences in therapeutic effects of D. officinale stems grown in various cultivation environments.

Results

A total of 1929 primary and secondary metabolites were identified. Compared to the tree epiphytic and greenhouse environments, 58 primary and secondary metabolites were up-regulated in the stone epiphytic environment. Among these, 7 amino acids and their derivatives were exclusively found as up-regulated primary metabolites, while 18 flavonoids constituted the main up-regulated secondary metabolites. The binding affinities of the 18 flavonoids to the core targets (MAOA and TNF) were superior to those of other up-regulated metabolites, and they can be utilized in quality difference studies, particularly nicotiflorin and isoquercitrin. Stems grown in the stone epiphytic environment showed a superior protective effect on chronic atrophic gastritis cells compared to the other two environments. This was associated with increased binding of differential metabolites to targets such as MAOA and TNF and decreased binding to targets such as SRC and PTGS2.

Discussion

The composition and content of metabolites in D. officinale stems are influenced by the cultivation environment, which in turn affects the therapeutic effects of the stems. The change of the target preference could be the reason for the difference in drug efficacy. This study introduces a novel approach for distinguishing the quality of D. officinale stems grown under different cultivation environments and exploring the variations in their therapeutic effects.

Cadmium spurred Microcystis aeruginosa to unleash more toxic metabolites

Cyanobacterial harmful algal blooms (cHABs), normally dominated by Microcystis aeruginosa, pose a threat to aquatic ecosystems due to the release of various harmful metabolites. Cadmium (Cd), a heavy metal commonly found in surface water and sediments, often coincides with cHABs in eutrophic lakes. However, the ecotoxicological effects of Cd on M. aeruginosa and the potential for combined toxicity are not yet fully understood. In this study, we determined the effective concentrations of cadmium from 10 % (EC10) to 50 % (EC50) for M. aeruginosa based on cell density inhibition. We then conducted a combined analysis focusing on the impact of a low dose Cd (EC10, 139 μg/L) on the physiological factors, transcriptome and both intracellular and extracellular metabolites of M. aeruginosa. We found that Cd treatment decreased M. aeruginosa chlorophyll a content by 24.5 %, which coincided with the suppression of genes linked to ribosomal and photosynthesis pathways. However, Cd exposure stimulated the synthesis and extracellular release of cellular compounds by enhancing amino acid and carbohydrate metabolism. This led to elevated extracellular levels of amino acids, organic acids, and secondary metabolites - including peptides, lipids, benzenoids, terpenes, sterols, and glycosides - which could serve as potential toxic metabolites of cyanobacteria. These changes were driven by the activation of osmoregulatory mechanisms, antioxidant-related amino acids, and ATP-binding cassette transport and secretion systems. Our research indicated that low Cd concentrations could stimulate the synthesis and release of toxic metabolites and exacerbate cHAB threats in eutrophic lakes, underscoring the importance of addressing multiple stressors in freshwater environments.

Comprehensive review of mapping climate change impacts on tea cultivation: bibliometric and content analysis of trends, influences, adaptation strategies, and future directions

Climate change has a profound impact on tea cultivation, posing significant challenges to yield, quality, and sustainability due to stressors such as drought, temperature fluctuations, and elevated CO₂ levels. This study aims to address these challenges by identifying and synthesizing key themes, influential contributions, and effective adaptation strategies for mitigating the impacts of climate change on tea production. A systematic bibliometric and content analysis was conducted on 328 peer-reviewed documents (2004-2023), following the PRISMA methodology. Performance analysis using Bibliometrix examined trends in publication output, leading contributors, and geographical distribution, while science mapping with VOSviewer revealed collaboration networks and thematic clusters. A detailed review of highly cited studies highlighted the primary climate variables affecting tea cultivation and identified innovative adaptation strategies, as well as critical knowledge gaps. The results show significant progress in understanding the physiological, biochemical, and molecular responses of tea plants to climate-induced stressors, including antioxidant mechanisms, secondary metabolite regulation, and genomic adaptations. Despite these advancements, challenges remain, particularly regarding the combined effects of multiple stressors, long-term adaptation strategies, and the socioeconomic implications of climate change. The findings underscore the need for interdisciplinary approaches that integrate molecular, ecological, and socioeconomic research to address these issues. This study provides a solid foundation for guiding future research, fostering innovative adaptation strategies, and informing policy interventions to ensure sustainable tea production in a changing climate.

Redefining the Tea Green Leafhopper: Empoasca onukii Matsuda (Hemiptera: Cicadellidae) as a Vital Asset in Premium Tea Production

This review explores the evolving role of the tea green leafhopper, Empoasca onukii, in the tea industry, transitioning from a recognized pest to a significant enhancer of tea quality. Recent research highlights how its feeding behavior stimulates the production of desirable secondary metabolites, thereby improving the flavor profiles and market value of premium teas, particularly varieties like Taiwan's "Oriental Beauty". As consumer demand for unique and artisanal teas rises, the economic benefits associated with E. onukii are becoming increasingly evident, prompting farmers to adopt sustainable agricultural practices that often involve reduced pesticide use. Furthermore, the dynamic interplay between climatic factors, E. onukii population dynamics, and tea cultivation practices necessitates integrated pest management strategies that balance the beneficial and detrimental impacts of this leafhopper. Understanding these complexities not only fosters sustainable production methods but also opens niche markets, benefiting local economies and promoting both economic viability and environmental sustainability in the tea industry.

Transcriptome and metabolism study reveals impact of nitrogen fertilizer on triticale

Autumn-sown forage triticale can effectively leverage the optimal light and heat conditions in Ningxia, a region that boasts an abundance of light and heat resources sufficient for a single seasonal crop, but limited for two seasons. This not only fully utilizes the limited growing season but also significantly improves grass yield and economic efficiency per unit area. To enhance triticale yield in low-light and low-temperature environments, we investigated the impact of applying different concentrations of nitrogen fertilizer on triticale forage yield. Our findings revealed that nitrogen fertilizer application significantly increased triticale biomass, with the N4 treatment group exhibiting the most profound effect. To further explore the mechanisms behind nitrogen fertilizer's regulation of triticale growth and development, we conducted transcriptomic and metabolomic studies. These studies revealed that nitrogen fertilizer application significantly heightened transcription activity and protein synthesis in triticale, fostering the development of its seeds. Additionally, appropriate concentrations of nitrogen fertilizer significantly promoted photosynthesis. Metabolomic analysis revealed that nitrogen fertilizer application increased the levels of proline and O-phosphoethanolamine, enhancing triticale's stress resistance and supporting its growth and development under adverse conditions.

Investigating the mechanism of auxin-mediated fulvic acid-regulated root growth in Oryza sativa through physiological and transcriptomic analyses

As rice is one of the most crucial staple food sources worldwide, enhancing rice yield is paramount for ensuring global food security. Fulvic acid (FA), serving as a plant growth promoter and organic fertilizer, holds significant practical importance in studying its impact on rice root growth for improving rice yield and quality. This study investigated the effects of different concentrations of FA on the growth of rice seedlings. The results indicated that 0.05 g/L FA could promote the growth of rice seedlings, while 0.5 g/L FA inhibited root growth, reduced cell activity and enzyme activity in the root tips, and accumulated reactive oxygen species in root cells. To further elucidate the molecular mechanisms underlying these effects, we performed transcriptomic analysis and found that auxin (Aux) may be involved in the growth process mediated by FA. Furthermore, transcriptome heatmap analysis revealed a significant upregulation of the Aux/indoleacetic acid (Aux/IAA) gene family after FA treatment, suggesting that this gene family plays a crucial role in the impact of FA on root growth. Additionally, by detecting endogenous Aux content and adding exogenous Aux inhibitors, we confirmed the involvement of FA in rice seedling root growth as well as in the synthesis and transduction pathway of Aux.

Multi-Omics Analysis Provides Insights into Green Soybean in Response to Cold Stress

Green soybean (Glycine max (L.) Merrill) is a highly nutritious food that is a good source of protein and fiber. However, it is sensitive to low temperatures during the growing season, and enhancing cold tolerance has become a research hotspot for breeding improvement. Background/Objectives: The underlying molecular mechanisms of cold tolerance in green soybean are not well understood. Methods: Here, a comprehensive analysis of transcriptome and metabolome was performed on a cold-tolerant cultivar treated at 10 °C for 24 h. Results: Compared to control groups, we identified 17,011 differentially expressed genes (DEGs) and 129 differentially expressed metabolites (DEMs). The DEGs and DEMs were further subjected to KEGG functional analysis. Finally, 11 metabolites (such as sucrose, lactose, melibiose, and dehydroascorbate) and 17 genes (such as GOLS, GLA, UGDH, and ALDH) were selected as candidates associated with cold tolerance. Notably, the identified metabolites and genes were enriched in two common pathways: 'galactose metabolism' and 'ascorbate and aldarate metabolism'. Conclusions: The findings suggest that green soybean modulates the galactose metabolism and ascorbate and aldarate metabolism pathways to cope with cold stress. This study contributes to a deeper understanding of the complex molecular mechanisms enabling green soybeans to better avoid low-temperature damage.

Evaluation of Two Different Methods of Fulvic Acid Application (Seed Priming and Foliar Spray) on Growth, Yield, and Nutritional Quality of Pea (Pisum sativum L.)

Pea is a commercially significant legume that is widely utilized worldwide and has a elevated amount of nutrition and bioactive components. Its consumption is attributed to a number of health benefits and its potential as a functional food. Fulvic acid can be used as a bio-stimulant to promote plant growth and increase nutrient availability and uptake. A field experiment was designed during two subsequent cropping seasons (i.e., 2022-23 and 2023-24) to evaluate the impact of two methods of fulvic acid application of seed priming and foliar spray on the growth, yield, antioxidant content, and nutritional value of pea (Pisum sativum L.) plants. The seeds were primed with fulvic acid at 1.5, 3 g L-1, and water, while a foliar spray of fulvic acid with the same doses was performed on the seedlings of non-primed seeds. The results obtained exhibited that the seed priming technique with fulvic acid outperformed the fulvic acid foliar applications. The increase in the fulvic acid dose to 3 g L-1 in both application techniques exhibited the highest plant growth, heaviest fresh and dry weights, and highest green seed yield. The maximum growth parameters were recorded after the foliar spray treatment at a dose of 3 g L-1, as it led to improvement in the growth parameters, leaf pigments, and total carbohydrates. The highest number of seeds per pod, number of pods per plant, 100-seed weight, and seed yield were obtained by the seed priming technique. From the results obtained, it may be concluded that the application of fulvic acid at 3 g L-1 via the seed priming technique is beneficial for enhancing the productivity of peas.

Multi-Omics Analysis Reveals the Mechanism by Which RpACBP3 Overexpression Contributes to the Response of Robinia pseudoacacia to Pb Stress

Acyl-CoA-binding protein (ACBP) genes have been implicated in lead enrichment and translocation in plants; however, the mechanisms by which these genes contribute to the response to heavy metal stress in various taxa have not been determined. In this study, the molecular mechanisms underlying the response of Robinia pseudoacacia, an economically important deciduous tree, to Pb stress were examined using transcriptomic and metabolomic analyses. RpACBP3 overexpression increased Pb enrichment, translocation, and tolerance. After Pb stress for 3 days, 1125 differentially expressed genes (DEGs) and 485 differentially accumulated metabolites (DAMs) were identified between wild-type and RpACBP3-overexpressing R. pseudoacacia strains; after Pb stress for 45 days, 1746 DEGs and 341 DAMs were identified. Joint omics analyses showed that the DEGs and DAMs were co-enriched in α-linoleic acid metabolism and flavonoid biosynthesis pathways. In particular, DEGs and DAMs involved in α-linoleic acid metabolism and flavonoid biosynthesis were up- and down-regulated, respectively. Moreover, RpACBP3 overexpression enhanced the ability to scavenge reactive oxygen species and repair cell membranes under stress by regulating LOX gene expression and increasing the phosphatidylcholine content, thereby improving the tolerance to Pb stress. These findings lay a theoretical foundation for the future application of RpACBP3 genes in plant germplasm resource creation and phytoremediation of Pb contaminated soil in which R. pseudoacacia grow.

Integrative transcriptome and metabolome analysis reveals the mechanism of fulvic acid alleviating drought stress in oat

Drought stress inhibits oat growth and yield. The application of fulvic acid (FA) can improve the drought resistance of oats, but the corresponding molecular mechanism of FA-mediated drought resistance remains unclear. Here, we studied the effects of FA on the drought tolerance of oat leaves through physiological, transcriptomic, and metabolomics analyses, and identified FA-induced genes and metabolites related to drought tolerance. Physiological analysis showed that under drought stress, FA increased the relative water and chlorophyll contents of oat leaves, enhanced the activity of antioxidant enzymes (SOD, POD, PAL, CAT and 4CL), inhibited the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and dehydroascorbic acid (DHA), reduced the degree of oxidative damage in oat leaves, improved the drought resistance of oats, and promoted the growth of oat plants. Transcriptome and metabolite analyses revealed 652 differentially expressed genes (DEGs) and 571 differentially expressed metabolites (DEMs) in FA-treated oat leaves under drought stress. These DEGs and DEMs are involved in a variety of biological processes, such as phenylspropanoid biosynthesis and glutathione metabolism pathways. Additionally, FA may be involved in regulating the role of DEGs and DEMs in phenylpropanoid biosynthesis and glutathione metabolism under drought stress. In conclusion, our results suggest that FA promotes oat growth under drought stress by attenuating membrane lipid peroxidation and regulating the antioxidant system, phenylpropanoid biosynthesis, and glutathione metabolism pathways in oat leaves. This study provides new insights into the complex mechanisms by which FA improves drought tolerance in crops.

Fulvic acid application increases rice seedlings performance under low phosphorus stress

BACKGROUND

Fulvic acid enhances plant growth and interacts synergistically with phosphate fertilizer to alleviate the agricultural production problem of low phosphorus fertilizer utilization efficiency. However, the underlying mechanism of its action remains poorly understood. In this study, we investigated the impact of fulvic acid application with varying concentrations (0, 40, 60, 80 and 120 mg/L) on rice performance in plants grown in a hydroponic system subjected to low phosphorus stress. The rice growth phenotypes, biomass, root morphology, phosphorus uptake, and the impact of fulvic acid on the rhizosphere environment of rice, were assessed.

RESULTS

The findings showed that adding appropriate concentrations of exogenous fulvic acid could promote the growth performance of rice under low phosphorus stress. Particularly at T1 (40 mg/L) and T2 (60 mg/L) over the control effectively increased rice biomass by 25.42% and 24.56%, respectively. Fulvic acid treatments stimulated root morphogenesis, up-regulated phosphate transporter genes, and facilitated phosphorus absorption and accumulation. Especially T1 (20.52%), T2 (18.10%) and T3 (20.48%) treatments significantly increased phosphorus uptake in rice, thereby alleviating low phosphorus stress. Additionally, fulvic acid elevated organic acids concentration in roots and up-regulated plasma membrane H+-ATPase genes, promoting organic acids secretion. This metabolic alteration can also alleviate low phosphorus stress in rice.

CONCLUSIONS

The effect of exogenous fulvic acid on physiological indicators is concentration-dependent under low phosphorus stress, enhances rice performance and reduces reliance on phosphorus fertilizer. This provides new insights to shed light on the mechanism of alleviating low phosphorus stress in rice through fulvic acid application, an eco-friendly tool.

Next generation plant biostimulants & genome sequencing strategies for sustainable agriculture development

The best environment for plant growth and development contains certain essential metabolites. A broad category of metabolites known as "plant biostimulants" (PBs) includes biomolecules such as proteins, carbohydrates, lipids, and other secondary metabolites related to groups of terpenes, specific nitrogen-containing compounds, and benzene ring-conjugated compounds. The formation of biomolecules depends on both biotic and abiotic factors, such as the release of PB by plants, animals, and microorganisms, or it can result from the control of temperature, humidity, and pressure in the atmosphere, in the case of humic substances (HSs). Understanding the genomic outputs of the concerned organism (may be plants or others than them) becomes crucial for identifying the underlying behaviors that lead to the synthesis of these complex compounds. For the purposes of achieving the objectives of sustainable agriculture, detailed research on PBs is essential because they aid in increasing yield and other growth patterns of agro-economic crops. The regulation of homeostasis in the plant-soil-microbe system for the survival of humans and other animals is mediated by the action of plant biostimulants, as considered essential for the growth of plants. The genomic size and gene operons for functional and regulation control have so far been revealed through technological implementations, but important gene annotations are still lacking, causing a delay in revealing the information. Next-generation sequencing techniques, such as nanopore, nanoball, and Illumina, are essential in troubleshooting the information gaps. These technical advancements have greatly expanded the candidate gene openings. The secondary metabolites being important precursors need to be studied in a much wider scale for accurate calculations of biochemical reactions, taking place inside and outside the synthesized living cell. The present review highlights the sequencing techniques to provide a foundation of opportunity generation for agricultural sustainability.

The Key Role of Plant Hormone Signaling Transduction and Flavonoid Biosynthesis Pathways in the Response of Chinese Pine (Pinus tabuliformis) to Feeding Stimulation by Pine Caterpillar (Dendrolimus tabulaeformis)

In nature, plants have developed a series of resistance mechanisms to face various external stresses. As understanding of the molecular mechanisms underlying plant resistance continues to deepen, exploring endogenous resistance in plants has become a hot topic in this field. Despite the multitude of studies on plant-induced resistance, how plants respond to stress under natural conditions remains relatively unclear. To address this gap, we investigated Chinese pine (Pinus tabuliformis) using pine caterpillar (Dendrolimus tabulaeformis) under natural conditions. Healthy Chinese pine trees, approximately 10 years old, were selected for studying induced resistance in Huangtuliangzi Forestry, Pingquan City, Chengde City, Hebei Province, China. Pine needles were collected at 2 h and 8 h after feeding stimulation (FS) via 10 pine caterpillars and leaf clipping control (LCC), to simulate mechanical damage caused by insect chewing for the quantification of plant hormones and transcriptome and metabolome assays. The results show that the different modes of treatments significantly influence the contents of JA and SA in time following treatment. Three types of differentially accumulated metabolites (DAMs) were found to be involved in the initial response, namely phenolic acids, lipids, and flavonoids. Weighted gene co-expression network analysis indicated that 722 differentially expressed genes (DEGs) are positively related to feeding stimulation and the specific enriched pathways are plant hormone signal transduction and flavonoid biosynthesis, among others. Two TIFY transcription factors (PtTIFY54 and PtTIFY22) and a MYB transcription factor (PtMYB26) were found to be involved in the interaction between plant hormones, mainly in the context of JA signal transduction and flavonoid biosynthesis. The results of this study provide an insight into how JA activates, serving as a reference for understanding the molecular mechanisms of resistance formation in conifers responding to mandibulate insects.

A Single Latent Plant Growth-Promoting Endophyte BH46 Enhances Houttuynia cordata Thunb. Yield and Quality

Plant growth-promoting endophytes (PGPE) can effectively regulate plant growth and metabolism. The regulation is modulated by metabolic signals, and the resulting metabolites can have considerable effects on the plant yield and quality. Here, tissue culture Houttuynia cordata Thunb., was inoculated with Rhizobium sp. (BH46) to determine the effect of BH46 on H. cordata growth and metabolism, and elucidate associated regulatory mechanisms. The results revealed that BH46 metabolized indole-3-acetic acid and induced 1-aminocyclopropane-1-carboxylate deaminase to decrease ethylene metabolism. Host peroxidase synthesis MPK3/MPK6 genes were significantly downregulated, whereas eight genes associated with auxins, cytokinins, abscisic acid, jasmonic acid, and antioxidant enzymes were significantly upregulated. Eight genes associated with flavonoid biosynthesis were significantly upregulated, with the CPY75B1 gene regulating the production of rutin and quercitrin and the HCT gene directly regulating the production of chlorogenic acid. Therefore, BH46 influences metabolic signals in H. cordata to modulate its growth and metabolism, in turn, enhancing yield and quality of H. cordata.

Endophytes Alleviate Drought-Derived Oxidative Damage in Achnatherum inebrians Plants Through Increasing Antioxidants and Regulating Host Stress Responses

Endophytes generally increase antioxidant contents of plants subjected to environmental stresses. However, the mechanisms by which endophytes alter the accumulation of antioxidants in plant tissues are not entirely clear. We hypothesized that, in stress situations, endophytes would simultaneously reduce oxidative damage and increase antioxidant contents of plants and that the accumulation of antioxidants would be a consequence of the endophyte ability to regulate the expression of plant antioxidant genes. We investigated the effects of the fungal endophyte Epichloë gansuensis (C.J. Li & Nan) on oxidative damage, antioxidant contents, and expression of representative genes associated with antioxidant pathways in Achnatherum inebrians (Hance) Keng plants subjected to low (15%) and high (60%) soil moisture conditions. Gene expression levels were measured using RNA-seq. As expected, the endophyte reduced the oxidative damage by 17.55% and increased the antioxidant contents by 53.14% (on average) in plants subjected to low soil moisture. In line with the accumulation of antioxidants in plant tissues, the endophyte increased the expression of most plant genes associated with the biosynthesis of antioxidants (e.g., MIOX, crtB, gpx) while it reduced the expression of plant genes related to the metabolization of antioxidants (e.g., GST, PRODH, ALDH). Our findings suggest that endophyte ability of increasing antioxidant contents in plants may reduce the oxidative damage caused by stresses and that the fungal regulation of plant antioxidants would partly explain the accumulation of these compounds in plant tissues.

Investigation of heat stress responses and adaptation mechanisms by integrative metabolome and transcriptome analysis in tea plants (Camellia sinensis)

Extreme high temperature has deleterious impact on the yield and quality of tea production, which has aroused the attention of growers and breeders. However, the mechanisms by which tea plant varieties respond to extreme environmental heat is not clear. In this study, we analyzed physiological indices, metabolites and transcriptome differences in three different heat-tolerant tea plant F1 hybrid progenies. Results showed that the antioxidant enzyme activity, proline, and malondialdehyde were significantly decreased in heat-sensitive 'FWS' variety, and the accumulation of reactive oxygen molecules such as H2O2 and O2- was remarkably increased during heat stress. Metabolomic analysis was used to investigate the metabolite accumulation pattern of different varieties in response to heat stress. The result showed that a total of 810 metabolites were identified and more than 300 metabolites were differentially accumulated. Transcriptional profiling of three tea varieties found that such genes encoding proteins with chaperon domains were preferentially expressed in heat-tolerant varieties under heat stress, including universal stress protein (USP32, USP-like), chaperonin-like protein 2 (CLP2), small heat shock protein (HSP18.1), and late embryogenesis abundant protein (LEA5). Combining metabolomic with transcriptomic analyses discovered that the flavonoids biosynthesis pathway was affected by heat stress and most flavonols were up-regulated in heat-tolerant varieties, which owe to the preferential expression of key FLS genes controlling flavonol biosynthesis. Take together, molecular chaperons, or chaperon-like proteins, flavonols accumulation collaboratively contributed to the heat stress adaptation in tea plant. The present study elucidated the differences in metabolite accumulation and gene expression patterns among three different heat-tolerant tea varieties under extreme ambient high temperatures, which helps to reveal the regulatory mechanisms of tea plant adaptation to heat stress, and provides a reference for the breeding of heat-tolerant tea plant varieties.

Comprehensive widely targeted metabolomics to decipher the molecular mechanisms of Dioscorea opposita thunb. cv. Tiegun quality formation during harvest

Dioscorea opposita Thumb. cv. Tiegun is commonly consumed as both food and traditional Chinese medicine, which has a history of more than two thousand years. Harvest time directly affects its quality, but few studies have focused on metabolic changes during the harvesting process. Here, a comprehensive metabolomics approach was performed to determine the metabolic profiles during six harvest stages. Thirty eight metabolites with significant differences were determined as crucial participants. Related metabolic pathways including phenylalanine, tyrosine and tryptophan biosynthesis, stilbenoid, diarylheptanoid and gingerol biosynthesis, phenylpropanoid biosynthesis, flavonoid biosynthesis and tryptophan metabolism were the most active pathways during harvest. The results revealed that temperature has a significant impact on quality formation, which suggested that Dioscorea opposita thumb. cv. Tiegun harvested after frost had higher potential value of traditional Chinese medicine. This finding not only offered valuable guidance for yam production, but also provided essential information for assessing its quality.

Tea-Derived Polyphenols Enhance Drought Resistance of Tea Plants (Camellia sinensis) by Alleviating Jasmonate-Isoleucine Pathway and Flavonoid Metabolism Flow

Extreme drought weather has occurred frequently in recent years, resulting in serious yield loss in tea plantations. The study of drought in tea plantations is becoming more and more intensive, but there are fewer studies on drought-resistant measures applied in actual production. Therefore, in this study, we investigated the effect of exogenous tea polyphenols on the drought resistance of tea plant by pouring 100 mg·L-1 of exogenous tea polyphenols into the root under drought. The exogenous tea polyphenols were able to promote the closure of stomata and reduce water loss from leaves under drought stress. Drought-induced malondialdehyde (MDA) accumulation in tea leaves and roots was also significantly reduced by exogenous tea polyphenols. Combined transcriptomic and metabolomic analyses showed that exogenous tea polyphenols regulated the abnormal responses of photosynthetic and energy metabolism in leaves under drought conditions and alleviated sphingolipid metabolism, arginine metabolism, and glutathione metabolism in the root system, which enhanced the drought resistance of tea seedlings. Exogenous tea polyphenols induced jasmonic acid-isoleucine (JA-ILE) accumulation in the root system, and the jasmonic acid-isoleucine synthetase gene (TEA028623), jasmonic acid ZIM structural domain proteins (JAMs) synthesis genes (novel.22237, TEA001821), and the transcription factor MYC2 (TEA014288, TEA005840) were significantly up-regulated. Meanwhile, the flavonoid metabolic flow was significantly altered in the root; for example, the content of EGCG, ECG, and EGC was significantly increased. Thus, exogenous tea polyphenols enhance the drought resistance of tea plants through multiple pathways.

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.

Characterization of the interactions between Fulvic acid and Trypsin with Spectroscopic and Molecular Docking technology

The interaction mechanism between trypsin and fulvic acid was analyzed by multispectral method and molecular docking simulation. The fluorescence spectra showed that fulvic acid induced static quenching of trypsin. The validity of this conclusion was further substantiated through the computation of the binding constants. The thermodynamic parameters show that the reaction is mainly controlled by van der Waals force and hydrogen bond force, and the reaction is spontaneous. In addition, based on the obtained binding distance, there may be a non-radiative energy transfer between the two. The ultraviolet spectrum showed that fulvic acid could shift the absorption peak of trypsin, indicating that fulvic acid had an effect on the secondary structure of trypsin. According to the synchronous fluorescence spectrum results, fulvic acid primarily interacts with tryptophan residues in trypsin and induces alterations in their microenvironment. Three-dimensional fluorescence spectrum and circular dichroism further proves this conclusion. The molecular docking simulation reveals that the interaction between the two groups primarily arises from hydrogen bonding and van der Waals forces. The findings suggest that FA has the ability to induce conformational changes in trypsin's secondary structure.

Comparative transcriptome and metabolome analyses revealed quality difference between beauty tea processed through indoor withering and outdoor solar withering

BACKGROUND

Withering is the first processing procedure of beauty tea, and there are few reports on the impact of withering methods on the quality of beauty tea and its regulatory mechanisms.

RESULTS

Through comparison of fresh tea leaves (FT) with the leaves after indoor natural withering for 18 h (IWT-18) and outdoor solar withering for 6 h (OWT-6), which were collected at the end of the two withering processes, 17 282 and 13 984 differentially expressed genes (DEGs) were respectively screened and 267 and 154 differential metabolites (DMs) were respectively identified. The coexpression network revealed that a large number of DEGs and DMs were enriched in phenylpropanoid, flavonoid, and adenosine triphosphate binding cassette (ABC) transporter pathways, and the number of DMs and DEGs in IWT-18 versus FT exceeded that in OWT-6 versus FT. Both withering methods promoted a significant increase in content of phenylalanine and upregulation of β-glucoside expression in the phenylpropanoid metabolism pathway. Five theaflavin-type proanthocyanidins in the flavonoid synthesis pathway were more significantly accumulated in FT versus IWT-18 than in FT versus OWT-6. Meanwhile, both withering methods can affect the ABC transporter pathway to promote the accumulation of amino acids and their derivatives, but different withering methods affect different ABC transporter families. Outdoor withering with more severe abiotic stress has a greater impact on the ABCG family, whereas indoor withering has a more significant effect on the ABCC family. Sensory evaluation results showed that the dry tea of IWT-18 was slightly better than that of OWT-6 because of the longer withering time and more thorough substance transformation.

CONCLUSION

In conclusion, the formation of honey flavor in beauty tea may be closely related to the DEGs and DMs in these three pathways. Our research provides theoretical data support for further revealing the mechanism of quality formation during the withering process of beauty tea. © 2023 Society of Chemical Industry.

Integrated Metabolomic and Transcriptomic Analysis of Puerarin Biosynthesis in Pueraria montana var. thomsonii at Different Growth Stages

Puerarin, a class of isoflavonoid compounds concentrated in the roots of Puerarias, has antipyretic, sedative, and coronary blood-flow-increasing properties. Although the biosynthetic pathways of puerarin have been investigated by previous researchers, studies focusing on the influence of different growth stages on the accumulation of metabolites in the puerarin pathway are not detailed, and it is still controversial at the last step of the 8-C-glycosylation reaction. In this study, we conducted a comprehensive analysis of the metabolomic and transcriptomic changes in Pueraria montana var. thomsonii during two growing years, focusing on the vigorous growth and dormant stages, to elucidate the underlying mechanisms governing the changes in metabolite and gene expression within the puerarin biosynthesis pathway. In a comparison of the two growth stages in the two groups, puerarin and daidzin, the main downstream metabolites in the puerarin biosynthesis pathway, were found to accumulate mainly during the vigorous growth stage. We also identified 67 common differentially expressed genes in this pathway based on gene expression differences at different growth stages. Furthermore, we identified four candidate 8-C-GT genes that potentially contribute to the conversion of daidzein into puerarin and eight candidate 7-O-GT genes that may be involved in the conversion of daidzein into daidzin. A co-expression network analysis of important UGTs and HIDs along with daidzein and puerarin was conducted. Overall, our study contributes to the knowledge of puerarin biosynthesis and offers information about the stage at which the 8-C-glycosylation reaction occurs in biosynthesis. These findings provide valuable insights into the cultivation and quality enhancement of Pueraria montana var. thomsonii.

Proteomics and phosphoproteomics reveal the different drought-responsive mechanisms of priming with (Z)-3-hexenyl acetate in two tea cultivars

Drought is an important abiotic stress that constrains the quality and quantity of tea plants. The green leaf volatiles Z-3-hexenyl acetate (Z-3-HAC) have been reported to play an essential role in stress responses. However, the underlying mechanisms of drought tolerance in tea plants remain elusive. This study investigated the physiological, proteomic, and phosphoproteomic profiling of two tea plant varieties of Longjingchangye (LJCY) and Zhongcha 108 (ZC108) with contrasting drought tolerance characteristics under drought stress. Physiological data showed that spraying Z-3-HAC exhibited higher activities of superoxide dismutase (SOD) and catalase (CAT) in both LJCY and ZC108 but lower content of malondialdehyde (MDA) in LJCY under drought stress. The proteomic and phosphoproteomic analysis suggested that the drought tolerance mechanism of Z-3-HAC in LJCY and ZC108 was different. Proteomic analyses revealed that Z-3-HAC enhanced the drought tolerance of LJCY by fructose metabolism while enhancing the drought tolerance of ZC108 by promoting glucan biosynthesis and galactose metabolism. Furthermore, the differential abundance phosphoproteins (DAPPs) related to intracellular protein transmembrane transport and protein transmembrane transport were enriched in LJCY, and the regulation of response to osmotic stress and regulation of mRNA processing were enriched in ZC108. In addition, protein-phosphoprotein interactions (PPI) analyses suggested that energy metabolism and starch and sucrose metabolic processes might play critical roles in LJCY and ZC108, respectively. These results will help to understand the mechanisms by which Z-3-HAC enhances the drought resistance of tea plants at the protein level. SIGNIFICANT: Green leaf volatiles (GLVs) are important volatile organic compounds that play essential roles in plant defense against biotic and abiotic stresses. To understand the mechanisms of Z-3-HAC in improving the drought tolerance of tea plants, two contrasting drought tolerance varieties (LJCY and ZC108) were comparatively evaluated by proteomics and phosphoproteomics. This analysis evidenced changes in the abundance of proteins involved in energy metabolism and starch and sucrose metabolic processes in LJCY and ZC108, respectively. These proteins may elucidate new molecular aspects of the drought resistance mechanism of Z-3-HAC, providing a theoretical basis for drought resistance breeding of tea plants.

Preparation and Molecular Structural Characterization of Fulvic Acid Extracted from Different Types of Peat

Humic acid is a type of polymeric, organic weak acid mixture with a core aromatic structure and main-component oxygen-containing functional group. Fulvic acid is a type of humic substance that can be dissolved in acid, alkali, or water. This study discusses the influence of different peptides on the molecular structure of fulvic acid, which was extracted from herbaceous, woody, and mossy peats using alkaline dissolution and acid precipitation methods. Analyses using infrared, UV-Vis, 13C-NMR, and X-ray photoelectron spectroscopies, as well as X-ray diffraction (XRD), were conducted to compare the effects of different peat types on the content and molecular structure of fulvic acid. The woody peat fulvic acid content was the highest among all peat fulvic acids (0.38%). However, the yield of fulvic acid from herbaceous peat was the highest (2.53%). Herbaceous peat fulvic acid contains significant quantities of carbonyl, amino, methylene, carboxyl, and phenolic hydroxyl groups and ether bonds. Woody peat fulvic acid contains carbonyl and methoxy groups, benzenes, aromatic carbons, aromatic ethers, and phenols. The degree of aromatization of woody peat fulvic acid was the highest. Mossy peat fulvic acid contains high levels of hydroxy, methyl, methylene, and phenol groups and aromatic ethers. The structural differences in fulvic acids in the different types of peat were primarily manifested in the content of functional groups, with little influence from the types of functional groups. XRD analysis of the different peats revealed that their structures all comprised benzene rings. However, mossy peat contained more C=O and -COOH groups, whereas herbaceous peat contained more C-O groups.

Application of Multi-Perspectives in Tea Breeding and the Main Directions

Tea plants are an economically important crop and conducting research on tea breeding contributes to enhancing the yield and quality of tea leaves as well as breeding traits that satisfy the requirements of the public. This study reviews the current status of tea plants germplasm resources and their utilization, which has provided genetic material for the application of multi-omics, including genomics and transcriptomics in breeding. Various molecular markers for breeding were designed based on multi-omics, and available approaches in the direction of high yield, quality and resistance in tea plants breeding are proposed. Additionally, future breeding of tea plants based on single-cellomics, pangenomics, plant-microbe interactions and epigenetics are proposed and provided as references. This study aims to provide inspiration and guidance for advancing the development of genetic breeding in tea plants, as well as providing implications for breeding research in other crops.

Ganoderma boninense: general characteristics of pathogenicity and methods of control

Ganoderma boninense (G. boninense) is a soil-borne fungus threatening oil palm at the present. It causes basal stem rot disease on oil palm. Within six months, this fungus can cause an oil palm plantation to suffer a significant 43% economic loss. The high persistence and nature of spread of G. boninense in soil make control of the disease challenging. Therefore, controlling the pathogen requires a thorough understanding of the mechanisms that underlie pathogenicity as well as its interactions with host plants. In this paper, we present the general characteristics, the pathogenic mechanisms, and the host's defensive system of G. boninense. We also review upcoming and most promising techniques for disease management that will have the least negative effects on the environment and natural resources.

Fulvic Acid Improves Salinity Tolerance of Rice Seedlings: Evidence from Phenotypic Performance, Relevant Phenolic Acids, and Momilactones

Salinity is a severe stress that causes serious losses in rice production worldwide. This study, for the first time, investigated the effects of fulvic acid (FA) with various concentrations of 0.125, 0.25, 0.5, and 1.0 mL/L on the ability of three rice varieties, Koshihikari, Nipponbare, and Akitakomachi, to cope with a 10 dS/m salinity level. The results show that the T3 treatment (0.25 mL/L FA) is the most effective in stimulating the salinity tolerance of all three varieties by enhancing their growth performance. T3 also promotes phenolic accumulation in all three varieties. In particular, salicylic acid, a well-known salt-stress-resistant substance, is found to increase during salinity stress in Nipponbare and Akitakomachi treated with T3 by 88% and 60%, respectively, compared to crops receiving salinity treatment alone. Noticeably, the levels of momilactones A (MA) and B (MB) fall in salt-affected rice. However, their levels markedly rise in rice treated with T3 (by 50.49% and 32.20%, respectively, in Nipponbare, and by 67.76% and 47.27%, respectively, in Akitakomachi), compared to crops receiving salinity treatment alone. This implies that momilactone levels are proportional to rice tolerance against salinity. Our findings suggest that FA (0.25 mL/L) can effectively improve the salinity tolerance of rice seedlings even in the presence of a strong salt stress of 10 dS/m. Further studies on FA application in salt-affected rice fields should be conducted to confirm its practical implications.

Integrated metabolomic and transcriptomic analysis reveals the mechanism underlying the accumulation of anthocyanins and other flavonoids in the flesh and skin of teinturier grapes

Vitis vinifera 'Yan73' is a teinturier grape cultivar with red flesh. To explore the mechanism of berry color development, we performed an integrated flavonoid-targeted analysis of the metabolome and transcriptome of the skin and flesh of Yan73 berries collected at three phenological stages (E-L 31, E-L 35, and E-L 38). We identified 234 flavonoid-related metabolites, including 61 flavonols, 22 anthocyanins, and 61 other flavonoids. Most flavonoid metabolites accumulated continuously during berry development and attained the highest contents in the skin at E-L 38. The transcript level of crucial genes (C4H, CHS, and GST) was highest in the skin at E-L 38. Seventeen distinct modules were identified in a weighted gene correlation network analysis. The MEcoral1 module was probably correlated with flavonoid metabolism and comprised 623 unigenes. The findings provide insights into the regulation of flavonoid metabolites during berry development of Yan73 grape.

Integrated analysis of transcriptomics and metabolomics of peach under cold stress

Low temperature is one of the environmental factors that restrict the growth and geographical distribution of peach (Prunus persica L. Batsch). To explore the molecular mechanisms of peach brunches in response to cold, we analyzed the metabolomics and transcriptomics of 'Donghe No.1' (cold-tolerant, CT) and '21^st Century' (cold-sensitive, CS) treated by different temperatures (-5 to -30°C) for 12 h. Some cold-responsive metabolites (e.g., saccharides, phenolic acids and flavones) were identified with upregulation only in CT. Further, we identified 1991 cold tolerance associated genes in these samples and they were significantly enriched in the pathways of 'galactose metabolism', 'phenylpropanoid biosynthesis' and 'flavonoids biosynthesis'. Weighted gene correlation network analysis showed that soluble sugar, flavone, and lignin biosynthetic associated genes might play a key role in the cold tolerance of peach. In addition, several key genes (e.g., COMT, CCR, CAD, PER and F3'H) were substantially expressed more in CT than CS under cold stress, indicating that they might be major factors during the adaptation of peach to low temperature. This study will not only improve our understanding towards the molecular mechanisms of peach trees under cold stress but also contribute to the screening and breeding program of peach in the future.

Fulvic acid mitigates cadmium toxicity-induced damage in cucumber seedlings through the coordinated interaction of antioxidant enzymes, organic acid, and amino acid

Fulvic acid (FA) can significantly alleviate cadmium (Cd) stress, but the specific metabolic response of FA to Cd toxicity is still not clarified. In the present study, we used untargeted metabolomic [gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS)] analysis to profile cucumber metabolism in response to Cd stress after spray application of FA. Our results showed that 331 differentially enriched metabolites (DEMs) were identified in leaf materials. These DEMs were enriched in 21 shared pathways in comparative groups of "Cd treatment vs. the control treatment" and "FA + Cd treatment vs. the Cd treatment." Specifically, treatment with FA significantly enhanced the organic acid content (citric acid, isocitric acid, 2-oxoglutaric acid, fumaric acid, and malic acid), which would contribute to provide sufficient substrates for the tricarboxylic acid (TCA) cycle and amino acid biosynthesis, thereby ensuring the normal production of energy and amino acid. At the same time, FA significantly increased the amino acid content (aspartate, citrulline, histidine, leucine, and phenylalanine). The accumulation of organic acid and amino acid can act as chelating agents for heavy metal ions and as scavengers of reactive oxygen species (ROS), thereby reducing intracellular oxidative damage. Furthermore, the application of FA improves antioxidant enzymes and accelerates ROS clearance. The improved contents of organic acid and amino acid, and the increased activity of antioxidant enzymes both played a central role in the reduction of malondialdehyde (MDA, 14.08%), hydrogen peroxide (H₂O₂, 61.70%) contents, and superoxide anion radical (O₂^-, 30.41%) production rate in plants under Cd stress. Taken together, the present study demonstrates the effects of FA on the antioxidant capacity and carbohydrate and amino acid metabolism of cucumber seedlings exposed to Cd stress, which provides comprehensive insights into the regulation of plants' response to Cd toxicity with FA was applied in cucumber.

Integration of transcriptome and metabolome analyses reveals sorghum roots responding to cadmium stress through regulation of the flavonoid biosynthesis pathway

Cadmium (Cd) pollution is a serious threat to plant growth and human health. Although the mechanisms controlling the Cd response have been elucidated in other species, they remain unknown in Sorghum (Sorghum bicolor (L.) Moench), an important C₄ cereal crop. Here, one-week-old sorghum seedlings were exposed to different concentrations (0, 10, 20, 50, 100, and 150 μM) of CdCl₂ and the effects of these different concentrations on morphological responses were evaluated. Cd stress significantly decreased the activities of the enzymes peroxidase (POD), superoxide dismutase (SOD), glutathione S-transferase (GST) and catalase (CAT), and increased malondialdehyde (MDA) levels, leading to inhibition of plant height, decreases in lateral root density and plant biomass production. Based on these results, 10 μM Cd concentration was chosen for further transcription and metabolic analyses. A total of 2683 genes and 160 metabolites were found to have significant differential abundances between the control and Cd-treated groups. Multi-omics integrative analysis revealed that the flavonoid biosynthesis pathway plays a critical role in regulating Cd stress responses in sorghum. These results provide new insights into the mechanism underlying the response of sorghum to Cd.

Comparative Metabolomic Studies of Siberian Wildrye (Elymus sibiricus L.): A New Look at the Mechanism of Plant Drought Resistance

Drought is one of the most important factors affecting plant growth and production due to ongoing global climate change. Elymus sibiricus has been widely applied for ecological restoration and reseeding of degraded grassland in the Qinghai-Tibetan Plateau (QTP) because of its strong adaptability to barren, salted, and drought soils. To explore the mechanism of drought resistance in E. sibiricus, drought-tolerant and drought-sensitive genotypes of E. sibiricus were used in metabolomic studies under simulated long-term and short-term drought stress. A total of 1091 metabolites were detected, among which, 27 DMs were considered to be the key metabolites for drought resistance of E. sibiricus in weighted gene co-expression network analysis (WGCNA). Ten metabolites, including 3-amino-2-methylpropanoic acid, coniferin, R-aminobutyrate, and so on, and 12 metabolites, including L-Proline, L-histidine, N-acetylglycine, and so on, showed differential accumulation patterns under short-term and long-term drought stress, respectively, and thus, could be used as biomarkers for drought-tolerant and drought-sensitive E. sibiricus. In addition, different metabolic accumulation patterns and different drought response mechanisms were also found in drought-tolerant and drought-sensitive genotypes of E. sibiricus. Finally, we constructed metabolic pathways and metabolic patterns for the two genotypes. This metabolomic study on the drought stress response of E. sibiricus can provide resources and a reference for the breeding of new drought-tolerant cultivars of E. sibiricus.

Comparative Transcriptome Analysis Unveils the Molecular Mechanism Underlying Sepal Colour Changes under Acidic pH Substratum in Hydrangea macrophylla

The hydrangea (Hydrangea macrophylla (Thunb). Ser.), an ornamental plant, has good marketing potential and is known for its capacity to change the colour of its inflorescence depending on the pH of the cultivation media. The molecular mechanisms causing these changes are still uncertain. In the present study, transcriptome and targeted metabolic profiling were used to identify molecular changes in the RNAome of hydrangea plants cultured at two different pH levels. De novo assembly yielded 186,477 unigenes. Transcriptomic datasets provided a comprehensive and systemic overview of the dynamic networks of the gene expression underlying flower colour formation in hydrangeas. Weighted analyses of gene co-expression network identified candidate genes and hub genes from the modules linked closely to the hyper accumulation of Al³⁺ during different stages of flower development. F3'5'H, ANS, FLS, CHS, UA3GT, CHI, DFR, and F3H were enhanced significantly in the modules. In addition, MYB, bHLH, PAL6, PAL9, and WD40 were identified as hub genes. Thus, a hypothesis elucidating the colour change in the flowers of Al³⁺-treated plants was established. This study identified many potential key regulators of flower pigmentation, providing novel insights into the molecular networks in hydrangea flowers.

Transcriptome analysis reveals key drought-stress-responsive genes in soybean

Drought is the most common environmental stress and has had dramatic impacts on soybean (Glycine max L.) growth and yield worldwide. Therefore, to investigate the response mechanism underlying soybean resistance to drought stress, the drought-sensitive cultivar "Liaodou 15" was exposed to 7 (mild drought stress, LD), 17 (moderate drought stress, MD) and 27 (severe drought stress, SD) days of drought stress at the flowering stage followed by rehydration until harvest. A total of 2214, 3684 and 2985 differentially expressed genes (DEGs) in LD/CK1, MD/CK2, and SD/CK3, respectively, were identified by RNA-seq. Weighted gene co-expression network analysis (WGCNA) revealed the drought-response TFs such as WRKY (Glyma.15G021900, Glyma.15G006800), MYB (Glyma.15G190100, Glyma.15G237900), and bZIP (Glyma.15G114800), which may be regulated soybean drought resistance. Second, Glyma.08G176300 (NCED1), Glyma.03G222600 (SDR), Glyma.02G048400 (F3H), Glyma.14G221200 (CAD), Glyma.14G205200 (C4H), Glyma.19G105100 (CHS), Glyma.07G266200 (VTC) and Glyma.15G251500 (GST), which are involved in ABA and flavonoid biosynthesis and ascorbic acid and glutathione metabolism, were identified, suggesting that these metabolic pathways play key roles in the soybean response to drought. Finally, the soybean yield after rehydration was reduced by 50% under severe drought stress. Collectively, our study deepens the understanding of soybean drought resistance mechanisms and provides a theoretical basis for the soybean drought resistance molecular breeding and effectively adjusts water-saving irrigation for soybean under field production.

Integrated Analysis of Metabolome and Transcriptome Reveals the Difference in Flavonoid Biosynthesis between the Red- and White-Sarcocarp Pomelo Fruits

Flavonoids are bioactive secondary metabolites that play multiple roles in plants. However, studies on the flavonoid accumulation of the pomelo fruit are rare. In this study, we conducted a widely targeted metabolome analysis by using ultra-performance liquid chromatography and tandem mass spectrometry and identified 550 metabolites in the sarcocarp from red (C. maxima Merr. var. Tubtim Siam) and white pomelos (C. maxima (Burm.) Osbeck). A total of 263 significantly changed metabolites were detected from the 550 metabolites. Content analysis of the significantly changed metabolites (SCMs) showed that 138 SCMs were highly accumulated, whereas 125 SCMs were observed with lower content in red-sarcocarp pomelo. Importantly, 103 of the 263 SCMs were flavonoids, including 34 flavonoids, 29 flavonols, 18 flavonoid carbonosides, 9 dihydroflavones, 6 isoflavones, 5 anthocyanins, 1 dihydroflavonol, and 1 chalcone. Gene ontology analysis indicated that upregulated genes in red-sarcocarp pomelo were significantly enriched in GO terms related to flavonoids including flavonoid biosynthetic processes. Several important differentially expressed genes were detected in the correlation network, especially Cg2g009540 which is an orthologous gene of AtCHS, also detected in flavonoid biosynthesis networks, and which could be related to the high level of total flavonoids in the red-sarcocarp pomelo. Our study demonstrated the fluctuation of flavonoid biosynthesis in the two pomelo cultivars and laid a theoretical foundation for pomelo breeding to generate fruits with a high flavonoid content.

Diverse Physiological Roles of Flavonoids in Plant Environmental Stress Responses and Tolerance

Flavonoids are characterized as the low molecular weight polyphenolic compounds universally distributed in planta. They are a chemically varied group of secondary metabolites with a broad range of biological activity. The increasing amount of evidence has demonstrated the various physiological functions of flavonoids in stress response. In this paper, we provide a brief introduction to flavonoids' biochemistry and biosynthesis. Then, we review the recent findings on the alternation of flavonoid content under different stress conditions to come up with an overall picture of the mechanism of involvement of flavonoids in plants' response to various abiotic stresses. The participation of flavonoids in antioxidant systems, flavonoid-mediated response to different abiotic stresses, the involvement of flavonoids in stress signaling networks, and the physiological response of plants under stress conditions are discussed in this review. Moreover, molecular and genetic approaches to tailoring flavonoid biosynthesis and regulation under abiotic stress are addressed in this review.

Integrating transcriptomics and metabolomics to analyze quinoa (Chenopodium quinoa Willd.) responses to drought stress and rewatering

The crop production of quinoa (Chenopodium quinoa Willd.), the only plant meeting basic human nutritional requirements, is affected by drought stress. To better understand the drought tolerance mechanism of quinoa, we screened the drought-tolerant quinoa genotype "Dianli 129" and studied the seedling leaves of the drought-tolerant quinoa genotype after drought and rewatering treatments using transcriptomics and targeted metabolomics. Drought-treatment, drought control, rewatering-treated, and rewatered control were named as DR, DC, RW, and RC, respectively. Among four comparison groups, DC vs. DR, RC vs. RW, RW vs. DR, and RC vs. DC, we identified 10,292, 2,307, 12,368, and 3 differentially expressed genes (DEGs), and 215, 192, 132, and 19 differentially expressed metabolites (DEMs), respectively. A total of 38,670 genes and 142 pathways were annotated. The results of transcriptome and metabolome association analysis showed that gene-LOC110713661 and gene-LOC110738152 may be the key genes for drought tolerance in quinoa. Some metabolites accumulated in quinoa leaves in response to drought stress, and the plants recovered after rewatering. DEGs and DEMs participate in starch and sucrose metabolism and flavonoid biosynthesis, which are vital for improving drought tolerance in quinoa. Drought tolerance of quinoa was correlated with gene expression differences, metabolite accumulation and good recovery after rewatering. These findings improve our understanding of drought and rewatering responses in quinoa and have implications for the breeding of new drought-tolerance varieties while providing a theoretical basis for drought-tolerance varieties identification.

Genome-wide association mapping for wheat morphometric seed traits in Iranian landraces and cultivars under rain-fed and well-watered conditions

Seed traits in bread wheat are valuable to breeders and farmers, thus it is important exploring putative QTLs responsible for key traits to be used in breeding programs. GWAS was carried out using 298 bread wheat landraces and cultivars from Iran to uncover the genetic basis of seed characteristics in both rain-fed and well-watered environments. The analyses of linkage disequilibrium (LD) between marker pairs showed that the largest number of significant LDs in landraces (427,017) and cultivars (370,359) was recorded in genome B, and the strongest LD was identified on chromosome 4A (0.318). LD decay was higher in the B and A genomes, compared to the D genome. Mapping by using mrMLM (LOD > 3) and MLM (0.05/m, Bonferroni) led to 246 and 67 marker-trait associations (MTAs) under rain-fed, as well as 257 and 74 MTAs under well-watered conditions, respectively. The study found that 3VmrMLM correctly detected all types of loci and estimated their effects in an unbiased manner, with high power and accuracy and a low false positive rate, which led to the identification of 140 MTAs (LOD > 3) in all environments. Gene ontology revealed that 10 and 10 MTAs were found in protein-coding regions for rain-fed and well-watered conditions, respectively. The findings suggest that landraces studied in Iranian bread wheat germplasm possess valuable alleles, which are responsive to water-limited conditions. MTAs uncovered in this study can be exploited in the genome-mediated development of novel wheat cultivars.

Transcriptome Approach Reveals the Response Mechanism of Heimia myrtifolia (Lythraceae, Myrtales) to Drought Stress

Drought is a major environmental condition that inhibits the development and cultivation of Heimia myrtifolia. The molecular processes of drought resistance in H. myrtifolia remain unknown, which has limited its application. In our study, transcriptome analyzes were compared across three treatment groups (CK, T1, and T2), to investigate the molecular mechanism of drought resistance. Plant leaves wilted and drooped as the duration of drought stress increased. The relative water content of the leaves declined dramatically, and relative electrolyte leakage rose progressively. Using an RNA-Seq approach, a total of 62,015 unigenes with an average length of 1730 bp were found, with 86.61% of them annotated to seven databases, and 14,272 differentially expressed genes (DEGs) were identified in drought stress. GO and KEGG enrichment analyzes of the DEGs revealed significantly enriched KEGG pathways, including photosynthesis, photosynthetic antenna proteins, plant hormone signal transduction, glutathione metabolism, and ascorbate and aldarate metabolism. Abscisic acid signal transduction was the most prevalent in the plant hormone signal transduction pathway, and other plant hormone signal transductions were also involved in the drought stress response. The transcription factors (including MYB, NAC, WRKY, and bHLH) and related differential genes on significantly enriched pathways all played important roles in the drought process, such as photosynthesis-related genes and antioxidant enzyme genes. In conclusion, this study will provide several genetic resources for further investigation of the molecular processes that will be beneficial to H. myrtifolia cultivation and breeding.

Integration of Metabolomics and Transcriptomics for Investigating the Tolerance of Foxtail Millet (Setaria italica) to Atrazine Stress

Foxtail millet (Setaria italica) is a monotypic species widely planted in China. However, residual atrazine, a commonly used maize herbicide, in soil, is a major abiotic stress to millet. Here, we investigated atrazine tolerance in millet based on the field experiments, then obtained an atrazine-resistant variety (Gongai2, GA2) and an atrazine-sensitive variety (Longgu31, LG31). To examine the effects of atrazine on genes and metabolites in millet plants, we compared the transcriptomic and metabolomic profiles between GA2 and LG31 seedling leaves. The results showed that 2,208 differentially expressed genes (DEGs; 501 upregulated, 1,707 downregulated) and 192 differentially expressed metabolites (DEMs; 82 upregulated, 110 downregulate) were identified in atrazine-treated GA2, while in atrazine-treated LG31, 1,773 DEGs (761 upregulated, 1,012 downregulated) and 215 DEMs (95 upregulated, 120 downregulated) were identified. The bioinformatics analysis of DEGs and DEMs showed that many biosynthetic metabolism pathways were significantly enriched in GA2 and LG31, such as glutathione metabolism (oxiglutatione, γ-glutamylcysteine; GSTU6, GSTU1, GSTF1), amino acid biosynthesis (L-cysteine, N-acetyl-L-glutamic acid; ArgB, GS, hisC, POX1), and phenylpropanoid biosynthesis [trans-5-o-(4-coumaroyl)shikimate; HST, C3'H]. Meanwhile, the co-expression analysis indicated that GA2 plants had enhanced atrazine tolerance owing to improved glutathione metabolism and proline biosynthesis, and the enrichment of scopoletin may help LG31 plants resist atrazine stress. Herein, we screened an atrazine-resistant millet variety and generated valuable information that may deepen our understanding of the complex molecular mechanism underlying the response to atrazine stress in millet.

Overexpression of Pennisetum purpureum CCoAOMT Contributes to Lignin Deposition and Drought Tolerance by Promoting the Accumulation of Flavonoids in Transgenic Tobacco

Elephant grass (Pennisetum purpureum) is a fast-growing and low-nutrient demand plant that is widely used as a forage grass and potential energy crop in tropical and subtropical regions of Asia, Africa, and the United States. Transgenic tobacco with the PpCCoAOMT gene from Pennisetum purpureum produces high lignin content that is associated with drought tolerance in relation to lower accumulation of reactive oxygen species (ROS), along with higher antioxidant enzyme activities and osmotic adjustment. In this study, transgenic tobacco plants revealed no obvious cost to plant growth when expressing the PpCCoAOMT gene. Metabolomic studies demonstrated that tobacco plants tolerant to drought stress accumulated flavonoids under normal and drought conditions, which likely explains the observed tolerance phenotype in wild-type tobacco. Our results suggest that plants overexpressing PpCCoAOMT were better able to cope with water deficit than were wild-type controls; metabolic flux was redirected within primary and specialized metabolism to induce metabolites related to defense to drought stress. These results could help to develop drought-resistant plants for agriculture in the future.

Drought and UV Radiation Stress Tolerance in Rice Is Improved by Overaccumulation of Non-Enzymatic Antioxidant Flavonoids

Drought and ultraviolet radiation (UV radiation) are the coexisting environmental factors that negatively affect plant growth and development via oxidative damage. Flavonoids are reactive, scavenging oxygen species (ROS) and UV radiation-absorbing compounds generated under stress conditions. We investigated the biosynthesis of kaempferol and quercetin in wild and flavanone 3-hydroxylase (F3H) overexpresser rice plants when drought and UV radiation stress were imposed individually and together. Phenotypic variation indicated that both kinds of stress highly reduced rice plant growth parameters in wild plants as compared to transgenic plants. When combined, the stressors adversely affected rice plant growth parameters more than when they were imposed individually. Overaccumulation of kaempferol and quercetin in transgenic plants demonstrated that both flavonoids were crucial for enhanced tolerance to such stresses. Oxidative activity assays showed that kaempferol and quercetin overaccumulation with strong non-enzymatic antioxidant activity mitigated the accumulation of ROS under drought and UV radiation stress. Lower contents of salicylic acid (SA) in transgenic plants indicated that flavonoid accumulation reduced stress, which led to the accumulation of low levels of SA. Transcriptional regulation of the dehydrin (DHN) and ultraviolet-B resistance 8 (UVR8) genes showed significant increases in transgenic plants compared to wild plants under stress. Taken together, these results confirm the usefulness of kaempferol and quercetin in enhancing tolerance to both drought and UV radiation stress.

Network pharmacology combined with molecular docking to explore the potential mechanisms for the antioxidant activity of Rheum tanguticum seeds

BACKGROUND

Rheum tanguticum (R. tanguticum) is an edible and medicinal plant that exhibits high antioxidant activity. The purpose of the present study was to investigate the bioactive components of its seeds and the potential mechanisms of antioxidant activity to provide a foundation for further developmental work on R. tanguticum seeds as a functional food.

METHODS

In this study, the antioxidant activities of R. tanguticum seeds were measured using DPPH, ABTS and FRAP assays. LC-Q-TOF/MS was used to identify the active compounds in the seeds, and Swiss Target Prediction was used to identify their potential targets. The DisGENET, DrugBank, OMIM and GeneCard databases were used to search for antioxidant-related targets.

RESULTS

The component-target-pathway network was constructed and included 5 compounds and 9 target genes. The hub genes included ESR1, APP, MAPK8, HSP90AA1, AKT1, MMP2, PTGS2, TGFB1 and JUN. The antioxidant activity signaling pathways of the compounds for the treatment of diseases were the cancer signaling pathway, estrogen signaling pathway, colorectal cancer signaling pathway, MAPK signaling pathway, etc. Molecular docking revealed that the compounds in R. tanguticum seeds could inhibit potential targets (AKT1, ESR1 and PTGS2).

CONCLUSION

Molecular docking studies revealed that the binding energy score between liriodenine and PTGS2 was the highest (8.16), followed by that of chrysophanol (7.10). This result supports the potential for PTGS2-targeted drug screening and design.

Plant Secondary Metabolites Produced in Response to Abiotic Stresses Has Potential Application in Pharmaceutical Product Development

Plant secondary metabolites (PSMs) are vital for human health and constitute the skeletal framework of many pharmaceutical drugs. Indeed, more than 25% of the existing drugs belong to PSMs. One of the continuing challenges for drug discovery and pharmaceutical industries is gaining access to natural products, including medicinal plants. This bottleneck is heightened for endangered species prohibited for large sample collection, even if they show biological hits. While cultivating the pharmaceutically interesting plant species may be a solution, it is not always possible to grow the organism outside its natural habitat. Plants affected by abiotic stress present a potential alternative source for drug discovery. In order to overcome abiotic environmental stressors, plants may mount a defense response by producing a diversity of PSMs to avoid cells and tissue damage. Plants either synthesize new chemicals or increase the concentration (in most instances) of existing chemicals, including the prominent bioactive lead compounds morphine, camptothecin, catharanthine, epicatechin-3-gallate (EGCG), quercetin, resveratrol, and kaempferol. Most PSMs produced under various abiotic stress conditions are plant defense chemicals and are functionally anti-inflammatory and antioxidative. The major PSM groups are terpenoids, followed by alkaloids and phenolic compounds. We have searched the literature on plants affected by abiotic stress (primarily studied in the simulated growth conditions) and their PSMs (including pharmacological activities) from PubMed, Scopus, MEDLINE Ovid, Google Scholar, Databases, and journal websites. We used search keywords: "stress-affected plants," "plant secondary metabolites, "abiotic stress," "climatic influence," "pharmacological activities," "bioactive compounds," "drug discovery," and "medicinal plants" and retrieved published literature between 1973 to 2021. This review provides an overview of variation in bioactive phytochemical production in plants under various abiotic stress and their potential in the biodiscovery of therapeutic drugs. We excluded studies on the effects of biotic stress on PSMs.

Physiological and proteomic analyses reveal the effects of exogenous nitrogen in diminishing Cd detoxification in Acacia auriculiformis

Cadmium (Cd) has toxic effects on plants. Nitrogen (N), an essential element, is critical for plant growth, development and stress response. However, their combined effects on woody plants, especially in N-fixing tree species is still poorly understood. Our previous study revealed that the fast-growing Acacia auriculiformis showed strong Cd tolerance but the underlying mechanisms was not clear, which constrained its use in mine land reclamation. Herein, we investigated the physiological and proteomic changes in A. auriculiformis leaves to reveal the mechanisms of Cd tolerance and toxicity without N fertilizer (treatment Cd) and with excess N fertilizer (treatment CdN). Results showed that Cd tolerance in A. auriculiformis was closely associated with the coordinated gas exchange and antioxidant defense reactions under Cd treatment alone. Exogenous excessive N, however, inhibited plant growth, increased Cd concentrations, and weaken photosynthetic performance, thus, aggregated the toxicity under Cd stress. Furthermore, the aggregated Cd toxicity was attributed to the depression in the abundance of proteins, as well as their corresponding genes, involved in photosynthesis, energy metabolism (oxidative phosphorylation, carbon metabolism, etc.), defense and stress response (antioxidants, flavonoids, etc.), plant hormone signal transduction (MAPK, STN, etc.), and ABC transporters. Collectively, this study unveils a previously unknown physiological and proteomic network that explains N diminishes Cd detoxification in A. auriculiformis. It may be counterproductive to apply N fertilizer to fast-growing, N-fixing trees planted for phytoremediation of Cd-contaminated soils.

Transcriptome Reveals the Dynamic Response Mechanism of Pearl Millet Roots under Drought Stress

Drought is a major threat to global agricultural production that limits the growth, development and survival rate of plants, leading to tremendous losses in yield. Pearl millet (Cenchrus americanus (L.) Morrone) has an excellent drought tolerance, and is an ideal plant material for studying the drought resistance of cereal crops. The roots are crucial organs of plants that experience drought stress, and the roots can sense and respond to such conditions. In this study, we explored the mechanism of drought tolerance of pearl millet by comparing transcriptomic data under normal conditions and drought treatment at four time points (24 h, 48 h, 96 h, and 144 h) in the roots during the seedling stage. A total of 1297, 2814, 7401, and 14,480 differentially expressed genes (DEGs) were found at 24 h, 48 h, 96 h, and 144 h, respectively. Based on Kyoto Encyclopedia of Genes and Genomes and Gene Ontology enrichment analyses, we found that many DEGs participated in plant hormone-related signaling pathways and the "oxidoreductase activity" pathway. These results should provide a theoretical basis to enhance drought resistance in other plant species.

CsGSTU8, a Glutathione S-Transferase From Camellia sinensis, Is Regulated by CsWRKY48 and Plays a Positive Role in Drought Tolerance

Glutathione S-transferases (GSTs) constitute a large family of enzymes with a wide range of cellular functions. Recently, plant GSTs have gained a great deal of attention due to their involvement in the detoxification of electrophilic xenobiotics and peroxides under adverse environmental conditions, such as salt, cold, UV-B and drought stress. A previous study reported that a GST gene (CsGSTU8) in tea plant was distinctly induced in response to drought, suggesting this gene plays a critical role in the drought stress response. In this study, by using quantitative real-time PCR (qRT-PCR) and β-glucuronidase (GUS) reporter lines, we further demonstrated that CsGSTU8 was upregulated in response to drought stress and exogenous abscisic acid (ABA) treatments. Overexpression of CsGSTU8 in Arabidopsis resulted in enhanced drought tolerance as indicated by the improved scavenging of excess amounts of reactive oxygen species (ROS) under drought conditions. Furthermore, we found that CsWRKY48 acts as a transcriptional activator and that its expression is induced in response to drought stress and ABA treatment. Electrophoretic mobility shift assays (EMSAs), dual-luciferase (LUC) assays and transient expression assays in tea plant leaves revealed that CsWRKY48 directly binds to the W-box elements in the promoter of CsGSTU8 and activates its expression. Taken together, our results provide additional knowledge of drought stress responses in tea plant.