Metabolite Profiling and Classification of Highbush Blueberry Leaves under Different Shade Treatments

Accumulation patterns of flavonoids and phenolic acids in different colored sweet potato flesh revealed based on untargeted metabolomics

Sweet potatoes are rich in flavonoids and phenolic acids, showing incomparable nutritional and health value. In this investigation, we comprehensively analyzed the secondary metabolite profiles in the flesh of different-colored sweet potato flesh. We determined the metabolomic profiles of white sweet potato flesh (BS), orange sweet potato flesh (CS), and purple sweet potato flesh (ZS) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The CS vs. BS, ZS vs. BS, and ZS vs. CS comparisons identified a total of 4447 secondary metabolites, including 1540, 1949, and 1931 differentially accumulated metabolites. Among them, there were significant differences in flavonoids and phenolic acids. There were 20 flavonoids and 13 phenolic acids that were common differential metabolites among the three comparison groups. The accumulation of paeoniflorin-like and delphinidin-like compounds may be responsible for the purple coloration of sweet potato flesh. These findings provide new rationale and insights for the development of functional foods for sweet potatoes.

List of compounds

Kaempferol (PubChem CID: 5280863); Peonidin 3-(6"-p-coumarylglucoside) (PubChem CID: 44256849); Swerchirin (PubChem CID: 5281660); Trilobatin (PubChem CID: 6451798); 3-Geranyl-4-hydroxybenzoate (PubChem CID: 54730540); Eupatorin (PubChem CID: 97214); Icaritin (PubChem CID: 5318980); Isorhamnetin (PubChem CID: 5281654); Glucoliquiritin apioside (PubChem CID: 74819335); Brazilin (PubChem CID: 73384).

LC-MS and GC-MS Metabolomics Analyses Revealed That Different Exogenous Substances Improved the Quality of Blueberry Fruits under Soil Cadmium Toxicity

Exogenous substances (ESs) can regulate plant growth and respond to environmental stress, but the effects of different ESs on blueberry fruit quality under soil cadmium (Cd) toxicity and related metabolic mechanisms are still unclear. In this study, four ES treatments [salicylic acid (SA), spermidine (Spd), 2,4-epibrassinolide (EBR), and melatonin (MT)] significantly increased blueberry fruit size, single-fruit weight, sweetness, and anthocyanin content under soil Cd toxicity and effectively reduced fruit Cd content to safe consumption levels by promoting mineral uptake (Ca, Mg, Mn, Cu and Zn). Furthermore, a total of 445, 360, 429, and 554 differentially abundant metabolites (DAMs) (LC-MS) and 63, 48, 79, and 73 DAMs (GC-MS) were identified from four comparison groups (SA/CK, Spd/CK, EBR/CK and MT/CK), respectively. The analyses revealed that ESs improved blueberry fruit quality and tolerance to Cd toxicity mainly by regulating the changes in metabolites related to ABC transporters, the TCA cycle, flavonoid biosynthesis, and phenylpropanoid biosynthesis.

Regulation of the Gene for Alanine Racemase Modulates Amino Acid Metabolism with Consequent Alterations in Cell Wall Properties and Adhesive Capability in Brucella spp

Brucella, a zoonotic facultative intracellular pathogenic bacterium, poses a significant threat both to human health and to the development of the livestock industry. Alanine racemase (Alr), the enzyme responsible for alanine racemization, plays a pivotal role in regulating virulence in this bacterium. Moreover, Brucella mutants with alr gene deletions (Δalr) exhibit potential as vaccine candidates. However, the mechanisms that underlie the detrimental effects of alr knockouts on Brucella pathogenicity remain elusive. Here, initially, we conducted a bioinformatics analysis of Alr, which demonstrated a high degree of conservation of the protein within Brucella spp. Subsequent metabolomics studies unveiled alterations in amino acid pathways following deletion of the alr gene. Furthermore, alr deletion in Brucella suis S2 induced decreased resistance to stress, antibiotics, and other factors. Transmission electron microscopy of simulated macrophage intracellular infection revealed damage to the cell wall in the Δalr strain, whereas propidium iodide staining and alkaline phosphatase and lactate dehydrogenase assays demonstrated alterations in cell membrane permeability. Changes in cell wall properties were revealed by measurements of cell surface hydrophobicity and zeta potential. Finally, the diminished adhesion capacity of the Δalr strain was shown by immunofluorescence and bacterial enumeration assays. In summary, our findings indicate that the alr gene that regulates amino acid metabolism in Brucella influences the properties of the cell wall, which modulates bacterial adherence capability. This study is the first demonstration that Alr impacts virulence by modulating bacterial metabolism, thereby providing novel insights into the pathogenic mechanisms of Brucella spp.

The Growth Characteristics and the Active Compounds of Cudrania tricuspidata Fruits in Different Cultivation Environments in South Korea

Cudrania tricuspidata is a traditional medicinal herb in East Asia. The compounds of plants vary depending on environmental factors, such as soil, temperature, drainage, and so on. However, few to no studies have been done on the correlation among environment, growth, and compounds in C. tricuspidata. Thus, we aimed to investigate their relationship. Samples of C. tricuspidata fruit and cultivation soil were collected from 28 cultivation sites in October 2021. Six growth characteristics, eleven soil physicochemical properties, seven meteorological data points, and three active compounds were investigated in this study. We developed and validated an optimized method for quantifying active compounds using UPLC and performed correlation analysis of the environment, growth characteristics, and active compounds. The UPLC-UV method for determining active compounds was validated by measuring the linearity, LOD, LOQ, precision, and accuracy using UPLC. The LOD and LOQ were 0.01-0.03 µg/mL and 0.04-0.09 µg/mL, respectively. The precision was acceptable with RSD% values less than 2%. The recoveries ranged from 97.25 to 104.98% with RSD values <2%, within the acceptable limits. The active compounds were negatively correlated with the size of the fruit, and the growth characteristics were negatively correlated with some environmental factors. The results of this study can be used as basic data for the standard cultural practices and quality control of C. tricuspidata fruits.

Metabolomics Analysis of Different Tissues of Lonicera japonica Thunb. Based on Liquid Chromatography with Mass Spectrometry

Lonicera japonica Thunb. (LJT) has been widely used as medicines or food additives in Asian countries for thousands of years. The flower buds are often medicinally used, and the other tissues are ignored. However, flowers, leaves and stems have also been reported to have antimicrobial, anti-inflammatory and antioxidant effects. In the current study, un-targeted metabolomics analysis was performed to investigate the metabolic difference among different tissues (flowers, flower buds, stems and leaves) of LJT based on liquid chromatography with mass spectrometry. A total of 171 metabolites were identified, including 28 flavonoids, 35 phenolic acids, 43 iridoids, 9 amino acids, 6 nucleotides, 16 fatty acids, 22 lipids and 12 others. Four new secondary metabolites were discovered. Some flavonoids and iridoids were not detected in leaves and stems. Principal component analysis showed significant differences among four different tissues. Some 27, 81, 113 differential metabolites were found between flowers/flower buds, leaves/flower buds, stems/flower buds, respectively. Primary metabolites showed a higher content in the flowers and flower buds. For the flavonoids, flavones were mainly accumulated in the leaves, flavonols were mainly accumulated in the flower buds, and acylated flavonol glucosides were mainly accumulated in the flowers. Most phenolic acids showed a higher content in the flowers or flower buds, while phenolic acid-glucosides showed significantly higher content in the flower buds. The most abundant iridoids in the LJT also showed a higher content in the flowers and flower buds. These results can provide new insights into the understanding of the metabolites changes in different tissues, and lay a theoretical foundation for the comprehensive utilization of LJT.

Metabolomic analysis reveals key metabolites alleviating green spots under exogenous sucrose spraying in air-curing cigar tobacco leaves

Cigar variety CX-010 tobacco leaves produce localized green spots during the air-curing period, and spraying exogenous sucrose effectively alleviates the occurrence of the green spots. To investigate the alleviation effect of exogenous sucrose spraying, the total water content and the number and size of green spots on tobacco leaves were investigated during the air-curing period under four treatments; CK (pure water), T1 (0.1 M sucrose), T2 (0.2 M sucrose) and T3 (0.4 M sucrose). The results showed that the total water content of tobacco leaves showed a trend of T3 < CK < T2 < T1 in the early air-curing stage, and the number and size of green spots showed a trend of T3 < T2 < T1 < CK. All sucrose treatments alleviated the green spot phenomenon, and T3 had the fewest green spots. Thus, the tobacco leaves of the T3 and CK treatments at two air-curing stages were used to perform metabolomics analysis with nontargeted liquid chromatography‒mass spectrometry to determine the physiological mechanism. A total of 259 and 178 differentially abundant metabolites (DAMs) between T3- and CK-treated tobacco leaves were identified in the early air-curing and the end of air-curing stages, respectively. These DAMs mainly included lipid and lipid-like molecules, carbohydrates, and organic acids and their derivatives. Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, the T3 treatment significantly altered carbohydrate metabolism (pentose phosphate pathway, sucrose and starch metabolism and galactose metabolism) and amino acid metabolism (tyrosine metabolism and tryptophan metabolism) in air-curing tobacco leaves. Sucrose treatment alleviated green spots by altering DAMs that affected chlorophyll degradation, such as tyrosine and citric acid, to promote the normal degradation of chlorophyll.

Analysis of flavonoid-related metabolites in different tissues and fruit developmental stages of blackberry based on metabolome analysis

Blackberry is an economically important shrub species of Rubus in the Rosaceae family. It is rich in phenolic compounds, which have many health effects and pharmaceutical value. The utilization of metabolites from various blackberry tissues is still in the primary stage of development, so investigating the metabolites in various tissues is of practical significance. In this study, nontargeted LC - MS metabolomics was used to identify and measure metabolites in the roots, stems, leaves and fruits (green, red, and black fruits) of blackberry "Chester". We found that 1,427 and 874 metabolites were annotated in the positive and negative ion modes (POS; NEG), respectively. Differentially abundant metabolites (DAMs) between the leaf and root groups were the most abundant (POS: 249; NEG: 141), and the DAMs between the green and red fruit groups were the least abundant (POS: 21; NEG: 14). Moreover, the DAMs in different fruit development stages were far less than those in different tissues. There were significant differences in flavonoid biosynthesis-related pathways among the comparison groups. Trend analysis showed that the profile 10 had the largest number of metabolites. This study provides a scientific basis for the classification and efficient utilization of resources in various tissues of blackberry plants and the directional development of blackberry products.

Isolation and identification of mycorrhizal helper bacteria of Vaccinium uliginosum and their interaction with mycorrhizal fungi

Mycorrhizal helper bacteria (MHB) can promote mycorrhizal fungal colonization and form mycorrhizal symbiosis structures. To investigate the effect of interactions between mycorrhizal beneficial microorganisms on the growth of blueberry, 45 strains of bacteria isolated from the rhizosphere soil of Vaccinium uliginosum were screened for potential MHB strains using the dry-plate confrontation assay and the bacterial extracellular metabolite promotion method. The results showed that the growth rate of mycelium of Oidiodendron maius 143, an ericoid mycorrhizal fungal strain, was increased by 33.33 and 77.77% for bacterial strains L6 and LM3, respectively, compared with the control in the dry-plate confrontation assay. In addition, the extracellular metabolites of L6 and LM3 significantly promoted the growth of O. maius 143 mycelium with an average growth rate of 40.9 and 57.1%, respectively, the cell wall-degrading enzyme activities and genes of O. maius 143 was significantly increased. Therefore, L6 and LM3 were preliminarily identified as potential MHB strains. In addition, the co-inoculated treatments significantly increased blueberry growth; increased the nitrate reductase, glutamate dehydrogenase, glutamine synthetase, and glutamate synthase activities in the leaves; and promoted nutrient uptake in blueberry. Based on the physiological, and 16S rDNA gene molecular analyses, we initially identified strain L6 as Paenarthrobacter nicotinovorans and LM3 as Bacillus circulans. Metabolomic analysis revealed that mycelial exudates contain large amounts of sugars, organic acids and amino acids, which can be used as substrates to stimulate the growth of MHB. In conclusion, L6 and LM3 and O. maius 143 promote each other's growth, while co-inoculation of L6 and LM3 with O. maius 143 can promote the growth of blueberry seedlings, providing a theoretical basis for further studies on the mechanism of ericoid mycorrhizal fungi-MHB-blueberry interactions. It laid the technical foundation for the exploitation of biocontrol strain resources and the development of biological fertilizer.

Comprehensive resistance evaluation of 15 blueberry cultivars under high soil pH stress based on growth phenotype and physiological traits

High soil pH is one of the main abiotic factors that negatively affects blueberry growth and cultivation. However, no comprehensive evaluation of the high soil pH tolerance of different blueberry cultivars has been conducted. Herein, 16 phenotypic and physiological indices of 15 blueberry cultivars were measured through pot experiments, and the high-pH soil tolerance coefficient (HSTC) was calculated based on these indices to comprehensively evaluate the high-soil-pH tolerance of plants. The results demonstrated that high soil pH stress inhibited blueberry 77.growth, and MDA, soluble sugar (SS), and soluble protein (SP) levels increased in leaves. Moreover, in all cultivars, CAT activity in the antioxidant system was enhanced, whereas SOD activity was reduced, and the relative expression levels of the antioxidant enzyme genes SOD and CAT showed similar changes. In addition, the leaf chlorophyll relative content (SPAD), net photosynthetic rate (P_n), transpiration rate (E), and stomatal conductance (G_s) decreased, while changes in the intercellular CO₂ concentration (C_i) were noted in different cultivars. Finally, according to the comprehensive evaluation value D obtained from the combination of principal component analysis (PCA) and membership function (MF), the 15 blueberry cultivars can be divided into 4 categories: high soil pH-tolerant type ['Briteblue' (highest D value 0.815)], intermediate tolerance type ('Zhaixuan 9', 'Zhaixuan 7', 'Emerald', 'Primadonna', 'Powderblue' and 'Chandler'), low high soil pH-tolerant type ('Brightwell', 'Gardenblue', 'Plolific' and 'Sharpblue') and high soil pH-sensitive type ['Legacy', 'Bluegold', 'Baldwin' and 'Anna' (lowest D value 0.166)]. Stepwise linear regression analysis revealed that plant height, SS, E, leaf length, C_i, SOD, and SPAD could be used to predict and evaluate the high soil pH tolerance of blueberry cultivars.

A physiological and metabolomic analysis reveals the effect of shading intensity on blueberry fruit quality

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The FT1 shading treatment yielded the largest values for blueberry single fruit weight.

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The highest total phenol, anthocyanin and vitamin C contents under the FT1 shading treatment.

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470 known metabolites were obtained from blueberry fruits.

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This study provides scientific basis for improving the quality of blueberry fruit.

With the advancement of blueberry industrialization, cultivation measures for obtaining high-quality fruits and technologies for obtaining high levels of the main secondary metabolites have become inevitable requirements for further development of the blueberry industry. This study applied different shading treatments and found that the FT1 shading treatment yielded the largest values for the single fruit weight, solid longitudinal diameter and transverse diameter of blueberry fruit as well as the highest solidity-acid ratio and total phenol and vitamin C contents. Moreover, 470 known metabolites were obtained from blueberry fruits. Interestingly, the differentially abundant metabolites related to ABC transporters, pyrimidine metabolism, and purine metabolism pathways were commonly identified from the three comparisons, which indicated that these three metabolic pathways in blueberry fruits are vulnerable to shading treatment. This study provides a theoretical basis for the application of summer shading to improve the quality and antioxidant substances of small berries.

Integrated metabolomic and transcriptomic analyses reveal different metabolite biosynthesis profiles of Juglans mandshurica in shade

Light is not only a very important source of energy for the normal growth and development of plants, but also a regulator of many development and metabolic processes. The mechanism of plant growth and development under low light conditions is an important scientific question. With the promulgation of the law to stop natural forest cutting, understory regeneration is an important method for artificial forest afforestation. Here, the growth and physiological indexes of Juglans mandshurica, an important hardwood species in Northeast China, were measured under different shade treatments. In addition, transcriptome and metabolome were compared to analyze the molecular mechanism of shade tolerance in J. mandshurica. The results showed that the seedling height of the shade treatment group was significantly higher than that of the control group, and the 50% light (L50) treatment was the highest. Compared with the control group, the contents of gibberellin, abscisic acid, brassinolide, chlorophyll a, and chlorophyll b in all shade treatments were significantly higher. However, the net photosynthetic rate and water use efficiency decreased with increasing shade. Furthermore, the transcriptome identified thousands of differentially expressed genes in three samples. Using enrichment analysis, we found that most of the differentially expressed genes were enriched in photosynthesis, plant hormone signal transduction and chlorophyll synthesis pathways, and the expression levels of many genes encoding transcription factors were also changed. In addition, analysis of differentially accumulated metabolites showed that a total of 470 differential metabolites were identified, and flavonoids were the major differential metabolites of J. mandshurica under light stress. These results improved our understanding of the molecular mechanism and metabolite accumulation under light stress in J. mandshurica.

Comparative Analysis of the Morphological, Physiological, Proteomic, and Metabolic Mechanisms of the "Biloxi" Blueberry Response to Shade Stress

Blueberry is an important small berry crop in economic forests. In hot summers, the top tip of blueberry often burns and withers due to water loss. Therefore, this study subjected blueberry to shading treatment in the summer to study the effects of different shading treatments on the growth, morphology, physiology and protein levels of the plant. The results showed that the 50% shading (T1) treatment yielded the highest average increases in plant height, crown width, and ground diameter of blueberry. Under the 80% shading (T2) treatment, the cells of the leaves dissolved, the morphology was incomplete, the vascular bundles disappeared, and no supporting skeleton was detected. As demonstrated by physiological and biochemical data and the proteome expression levels, the T1 shading treatment was beneficial to the growth of blueberry and significantly enriched the photosynthetic pathway and flavonoid biosynthesis. An analysis of the interaction network of differentially expressed proteins indicated that trans-cinnamate 4-monooxygenase (C4H, CYP73A), naringenin 3-dioxygenase (F3H) and bifunctional dihydroflavonol 4-reductase/flavanone 4-reductase (DFR) exhibited high connectivity and mutual regulation. In short, 50% shading can improve the growth index of blueberry and lead to an enrichment of flavonoid biosynthesis. This study provides a scientific basis for the breeding and summer protection of blueberry seedlings.

Effects of Fruit Shading on Gene and Protein Expression During Starch and Oil Accumulation in Developing Styrax tonkinensis Kernels

Styrax tonkinensis has great potential as a biofuel feedstock source having industrial oilseeds with excellent fatty acids (FAs) composition and good fuel properties. Photosynthesis in the developing pericarp could affect the carbon distribution in kernel. During kernel development, more carbon sources are allocated to starch rather than lipid, when the pericarp photosynthesis is reduced by fruit shading treatment. After shading the fruits at 50 days after flowering (DAF), samples of shaded fruit (FSK) and controls (CK) were collected at 80 DAF and analyzed using the proteomic method. We identified 3,181 proteins, of which 277 were differentially expressed proteins, all downregulated in the FSK group. There were 56 proteins found involved in carbohydrate metabolism and lipid biosynthesis leading to oil accumulation with their iTRAQ ratios of FSK/CK ranging from 0.7123 to 1.1075. According to the qRT-PCR analyses, the key genes related to FA and triacylglycerol (TAG) biosynthesis were significantly downregulated between 60 and 90 DAF especially at 80 DAF, while the key genes involved in starch biosynthesis and FA desaturase had no significant difference between the two groups at 80 DAF. Fruit shading is a negative treatment for lipid accumulation but not starch accumulation by restraining enzymic protein expression involved in FA and TAG biosynthesis during S. tonkinensis kernel development.