Organic Acid Metabolism Research Articles

Potential effects of Ag ion on the host by changing the structure of its gut microbiota

Silver (Ag) can change the structure of the gut microbiota (GM), but how such change may affect host health is unknown. In this study, mice were exposed to silver acetate daily for 120 days. During this period, Ag accumulation in the liver was measured, its effects on GM structure were analyzed, and potential metabolic changes in liver and serum were examined. Although Ag accumulation remained unchanged in most treatments, the ratio of Firmicutes to Bacteroidetes at the phylum level increased and changes in the relative abundance of 33 genera were detected, suggesting that Ag altered the energy metabolism of mice via changes in the gut GM. In serum and liver, 34 and 72 differentially expressed metabolites were identified, respectively. The KEGG pathways thus enriched mainly included those involving the metabolism of amino acids, organic acids, lipids, and purine. Strong correlations were found between 33 % of the microorganisms with altered relative abundances and 46 % of the differentially expressed metabolites. The resulting clusters yielded two communities responsible for host inflammation and energy metabolism. Overall, these results demonstrate potential effects of Ag on the host, by changing its GM structure, and the need to consider them when evaluating the health risk of Ag.

Integrated metabolomic analysis of Lactiplantibacillus plantarum NMGL2 reveals its survival and response to combinational cold and acidic conditions during storage of fermented milk

This study aimed to elucidate the molecular mechanism of Lactiplantibacillus plantarum NMGL2 (L. plantarum NMGL2) isolated from traditional Inner Mongolia cheese that how it survived under simultaneous cold and acid conditions, and developed potential protective strategies for bacterial survivability. L. plantarum NMGL2 was previously shown with numerous bioactivities such as antibiofilm, cholesterol-lowering effect, and bile acids binding capacity. In this study, non-directional UPLC-Q-TOF-MS/MS-based metabolomics was performed to investigate the metabolic variations in L. plantarum NMGL2 during refrigerated storage of the fermented milk to comprehend the underlying chemical process of bacterial resistance under the cold and acid conditions. Organic acids, fatty acids, polypeptides, amino acids, and carbohydrates were all among the 122 differently abundant metabolites discovered, which were mostly involved in organic acid, sugar, protein, amino acid, and purine metabolisms, This indicated that the bacteria counteracted the combinational coldness and acidity by increased biosynthesis of several important biomolecules such as glycolipids and glycoproteins for providing cell protection, glutamate for initiating cell deacidification process, and DNA for cell repairing, as well as cell membrane proteins and cell wall peptidoglycan. Western blot analysis confirmed up-regulation of PGRP protein, implicating that the cell wall peptidoglycan played a significant part in bacterial resistance under cold and acid conditions. Further SPME-GC/MS analysis demonstrated different volatile metabolites detected in the fermented milk during the storage, including 7 acids, 4 alcohols, 2 aldehydes, 4 ketones and 3 esters, which provided unique flavor characteristic of fermented milk for favorable consumer acceptance of the product. For the first time, our research elucidates the molecular mechanism by which L. plantarum survives simultaneous cold and acid conditions with development of potential protective strategies under such conditions.

Effects of artificial diet rearing during all instars on silk secretion and gene transcription in Bombyx mori (Lepidoptera: Bombycidae).

Silkworms (Bombyx mori) reared on artificial diets during all instars have the advantages of simplicity and efficiency, year-round production, and reduced risk of poisoning. However, low silk yield remains a challenge, limiting its industrial application. To address this issue, the spinning behavior, nutrient absorption, and transcriptomics of silkworms were investigated. Compared with silkworms reared on mulberry leaves during all instars, those fed with artificial diets showed significantly lower cocoon weight, cocoon shell weight, cocoon shell rate, and silk gland tissue somatic index at the end of the fifth instar (P < 0.01). The spinning duration and crawling distance of silkworms reared on artificial diets were also significantly lower than those reared on mulberry leaves (P < 0.01). Regarding nutrient absorption, the dietary efficiency indexes of silkworms fed with artificial diets were significantly lower than those fed with mulberry leaves, except for the efficiency conversion of digesta to cocoon (P < 0.01). Further RNA-Seq analysis revealed 386 differentially transcribed genes between the 2 groups, with 242 upregulated and 144 downregulated genes. GO enrichment analysis showed that differential transcriptional genes were mainly enriched in organic acid metabolism, oxidation-reduction, and drug catabolism. KEGG enrichment analysis showed that differential transcriptional genes were mainly enriched in genetic information processing and metabolism pathways. Our findings provide new insights into the silk secretion and can serve as a reference for future research and application of silkworms fed with artificial diets.

Guanxining injection alleviates fibrosis in heart failure mice and regulates SLC7A11/GPX4 axis.

Radix et Rhizoma Salviae Miltiorrhizae (Salvia miltiorrhiza Bge., Lamiaceae, Danshen in Chinese) and Chuanxiong Rhizoma (rhizomes of Ligusticum chuanxiong Hort., Apiaceae, Chuanxiong in Chinese) both are important traditional Chinese medicine (TCM) for activating blood and eliminating stasis. Danshen-chuanxiong herb pair has been used for more than 600 years in China. Guanxinning injection (GXN) is a Chinese clinical prescription refined from aqueous extract of Danshen and Chuanxiong at the ratio of 1:1 (w/w). GXN has been mainly used in the clinical therapy of angina, heart failure (HF) and chronic kidney disease in China for almost twenty years. This study aimed to explore the role of GXN on renal fibrosis in heart failure mice and the regulation of GXN on SLC7A11/GPX4 axis. The transverse aortic constriction model was used to mimic HF accompanied by kidney fibrosis model. GXN was administrated by tail vein injection in dose of 12.0, 6.0, 3.0mL/kg, respectively. Telmisartan (6.1mg/kg, gavage) was used as a positive control drug. Cardiac ultrasound indexes of ejection fraction (EF), cardiac output (CO), left ventricle volume (LV Vol), HF biomarker of pro-B type natriuretic peptide (Pro-BNP), kidney function index of serum creatinine (Scr), kidney fibrosis index of collagen volume fraction (CVF) and connective tissue growth factor (CTGF) were evaluated and contrasted. Metabolomic method was employed to analyze the endogenous metabolites changes in kidneys. Besides, contents of catalase (CAT), xanthine oxidase (XOD), nitricoxidesynthase (NOS), glutathione peroxidase 4 (GPX4), the x(c)(-) cysteine/glutamate antiporter (SLC7A11) and ferritin heavy chain (FTH1) in kidney were quantitatively analyzed. In addition, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to analyze the chemical composition of GXN and network pharmacology was used to predict possible mechanisms and the active ingredients of GXN. The cardiac function indexes of EF, CO and LV Vol, kidney functional indicators of Scr, the degree of kidney fibrosis indicators CVF and CTGF were all relieved to different extent for the model mice treated with GXN. 21 differential metabolites involved in redox regulation, energy metabolism, organic acid metabolism, nucleotide metabolism, etc were identified. Aspartic acid, homocysteine, glycine, and serine, methionine, purine, phenylalanine and tyrosine metabolism were found to be the core redox metabolic pathways regulated by GXN. Furthermore, GXN were found to increase CAT content, upregulate GPX4, SLC7A11 and FTH1 expression in kidney significantly. Not only that, GXN also showed good effect in down-regulating XOD and NOS contents in kidney. Besides, 35 chemical constituents were initially identified in GXN. Active ingredients of GXN-targets-related enzymes/transporters-metabolites network was established to find out that GPX4 was a core protein for GXN and the top 10 active ingredients with the most relevant to renal protective effects of GXN were rosmarinic acid, caffeic acid, ferulic acid, senkyunolide E, protocatechualdehyde, protocatechuic acid, danshensu, L-Ile, vanillic acid, salvianolic acid A. GXN could significantly maintain cardiac function and alleviate the progression of fibrosis in the kidney for HF mice, and the mechanisms of action were related to regulating redox metabolism of aspartate, glycine, serine, and cystine metabolism and SLC7A11/GPX4 axis in kidney. The cardio-renal protective effect of GXN may be attributed to multi-components like rosmarinic acid, caffeic acid, ferulic acid, senkyunolide E, protocatechualdehyde, protocatechuic acid, danshensu, L-Ile, vanillic acid, salvianolic acid A et al.

Effect of Low-Light Stress on Sugar and Acid Accumulation during Fruit Development and Ripening of Sweet Cherry

In the production process of sweet cherry, there are unreasonable planting densities and tree shape selections. With increasing tree age, the crown of the tree continues to expand and the tree body is prone to canopy closure, which leads to the inability to efficiently use space and light energy. Low-light has become a major limiting factor in the quality of sweet cherry. Therefore, we analyzed the changes of various physiological indicators and the transcriptome of ‘Hongdeng’ sweet cherry under shading treatment in this study to investigate the effects of low-light stress on the photosynthetic characteristics of sweet cherry leaves and fruit physiology and biochemistry. The results showed that shading significantly reduces the light capture capacity of leaves, damages the photosystem, reduces carbon assimilation capacity, and consumes the majority of the captured light energy as photochemical energy, thereby restricting the growth and development of leaves and reducing the accumulation of nutrients in fruits. Shading significantly reduced fruit weight, sugar content, and vitamin C content at maturity and significantly increased acid content. Transcriptomic data demonstrated that low-light stress produces a large number of differential genes related to carbon metabolism, organic acid metabolism, and stress resistance, thereby suggesting that low-light stress may affect the expression of these related genes and inclusions in the fruit. The results of this study will provide theoretical and technical support for the physiological response mechanism of low-light tolerance in sweet cherry, the selection and breeding of low-light tolerant sweet cherry varieties, and the cultivation of sweet cherry in facilities.

Acute Encephalopathy Caused by Inherited Metabolic Diseases.

Acute encephalopathy is a critical medical condition that typically affects previously healthy children and young adults and often results in death or severe neurological sequelae. Inherited metabolic diseases that can cause acute encephalopathy include urea cycle disorders, amino acid metabolism disorders, organic acid metabolism disorders, fatty acid metabolism disorders, mutations in the thiamine-transporter gene, and mitochondrial diseases. Although each inherited metabolic disease is rare, its overall incidence is reported as 1 in 800-2500 patients. This narrative review presents the common inherited metabolic diseases that cause acute encephalopathy. Since diagnosing inherited metabolic diseases requires specific testing, early metabolic/metanolic screening tests are required when an inherited metabolic disease is suspected. We also describe the symptoms and history associated with suspected inherited metabolic diseases, the various tests that should be conducted in case of suspicion, and treatment according to the disease group. Recent advancements made in the understanding of some of the inherited metabolic diseases that cause acute encephalopathy are also highlighted. Acute encephalopathy due to inherited metabolic diseases can have numerous different causes, and recognition of the possibility of an inherited metabolic disease as early as possible, obtaining appropriate specimens, and proceeding with testing and treatment in parallel are crucial in the management of these diseases.

KIF20A as a potential biomarker of renal and bladder cancers based on bioinformatics and experimental verification

Bladder cancer (BC) is a malignant tumor that occurs in the bladder wall and often appears in elderly individuals. Renal cancer (RC) arises from the renal tubular epithelium, but its molecular mechanism remains unclear.We downloaded RC datasets (GSE14762 and GSE53757) and a BC dataset (GSE121711) to screen differentially expressed genes (DEGs). We also performed weighted gene coexpression network analysis (WGCNA). We created a protein-protein interaction (PPI) network and performed functional enrichment analysis, such as gene set enrichment analysis (GSEA). Heatmaps were made for gene expression. Survival analysis and immunoinfiltration analysis were performed. Comparative toxicogenomics database (CTD) analysis was performed to find the relationship between disease and hub genes. Western blotting was performed to verify the role of KIF20A in apoptosis.A total of 764 DEGs were identified. The GSEA showed that the DEGs were mainly enriched in organic acid metabolism, drug metabolism, mitochondria, and metabolism of cysteine and methionine. The PPI network in GSE121711 showed that KIF20A was a hub gene of renal clear cell carcinoma. Where the expression level of KIF20A was higher, the prognosis of patients was worse. CTD analysis showed that KIF20A was associated with inflammation, proliferation, and apoptosis. KIF20A expression in the RC group was upregulated, as shown by western blotting. The core proteins (including pRB Ser 780, CyclinA, E2F1, CCNE1, and CCNE2) in the pRB Ser 780/CyclinA signaling pathway were also upregulated in the RC group.KIF20A might be a novel biomarker for researching renal and bladder cancers.

Analysis of organic acid metabolism reveals citric acid and malic acid play major roles in determining acid quality during the development of kiwifruit (Actinidia eriantha).

Actinidia eriantha is one of the most important kiwifruit species in Actinidia. The relative high accumulation of organic acids in fruit of A. eriantha is an unfavorable factor for organoleptic quality. To identify key metabolic enzymes and genes involved in organic acids accumulation during fruit development, physiological, biochemical, and molecular experiments were conducted for the dynamic fruit samples of a new kiwifruit cultivar, A. eriantha 'Ganlv 1'. The contents of citric acid and malic acid increased greatly during fruit development, while quinic acid content decreased obviously. Significant positive correlations were observed between fruit titratable acidity and the contents of both citric acid and malic acid, and a significant negative correlation was found between fruit titratable acidity and the quinic acid content. The high accumulation of citric acid was found to be caused by the increased activity of citrate synthase (CS), and the decreased activities of two degradation-related enzymes, mitochondrial aconitase and nicotinamide adenine dinucleotide (NAD)-dependent isocitrate dehydrogenase. In addition, the accumulation of malic acid depended mainly on the increased synthesis catalyzed by NAD-dependent malate dehydrogenase (NAD-MDH) and phosphoenolpyruvate carboxylase. Further analysis suggested that AeCS2 and AeMDH2 played pivotal roles in controlling the activities of CS and NAD-MDH respectively. The high accumulation level of citric acid relied on both the strong synthesis ability and the weak degradation ability. The accumulation level of malic acid was mainly affected by the synthesis. The novel information would be helpful for our understanding of the formation of fruit acidity quality. © 2023 Society of Chemical Industry.

Alternative oxidase 1a and 1d enable metabolic flexibility during Ala catabolism in Arabidopsis.

Ala is a central metabolite in leaf cells whose abundance is related to pyruvate (Pyr) metabolism and nocturnal respiration rates. Exposure of Arabidopsis (Arabidopsis thaliana) leaf disks to certain exogenous amino acids including Ala led to substantial increases in nighttime respiration rates as well as increases in alternative oxidase (AOX) 1d transcript and protein levels. During Ala treatment, AOX1d accumulation, but not AOX1a accumulation, was dependent upon the catabolism of Ala. Complete loss of AOX expression in aox1a aox1d leaf disks did not significantly affect oxygen consumption rates (OCR) under Ala treatment, indicating that AOX capacity per se was not essential for respiratory stimulation by Ala. Rather, Ala treatments caused induction of select antioxidant mechanisms in leaf disks, including a large increase of the ascorbate pool, which was substantially more oxidized in aox1a aox1d leaf disks. Furthermore, we observed differences in the accumulation of a sequence of TCA cycle intermediates from Pyr to 2-oxoglutarate (2-OG) in wild type (WT) upon Ala treatment that did not occur in aox1a aox1d leaf disks. The results indicate that AOX induction during enhanced Ala catabolism in leaves mediates mitochondrial redox status, allowing greater metabolic flexibility in mitochondrial organic acid metabolism.

Quantitative model for genome-wide cyclic AMP receptor protein binding site identification and characteristic analysis

Cyclic AMP receptor proteins (CRPs) are important transcription regulators in many species. The prediction of CRP-binding sites was mainly based on position-weighted matrixes (PWMs). Traditional prediction methods only considered known binding motifs, and their ability to discover inflexible binding patterns was limited. Thus, a novel CRP-binding site prediction model called CRPBSFinder was developed in this research, which combined the hidden Markov model, knowledge-based PWMs and structure-based binding affinity matrixes. We trained this model using validated CRP-binding data from Escherichia coli and evaluated it with computational and experimental methods. The result shows that the model not only can provide higher prediction performance than a classic method but also quantitatively indicates the binding affinity of transcription factor binding sites by prediction scores. The prediction result included not only the most knowns regulated genes but also 1089 novel CRP-regulated genes. The major regulatory roles of CRPs were divided into four classes: carbohydrate metabolism, organic acid metabolism, nitrogen compound metabolism and cellular transport. Several novel functions were also discovered, including heterocycle metabolic and response to stimulus. Based on the functional similarity of homologous CRPs, we applied the model to 35 other species. The prediction tool and the prediction results are online and are available at: https://awi.cuhk.edu.cn/∼CRPBSFinder.

A novel bacteriocin RSQ01 with antibacterial activity and its application and metabolomic mechanism in milk preservation

Milk poses a high-risk for microbial contamination (e.g., Salmonella Enteritidis) and spoilage. In recent years, lactic acid bacteria (LAB) bacteriocins have been widely acknowledged as the potential natural antibacterial substance in food biopreservation due to their excellent antibacterial effects. However, studies on the benefits of LAB bacteriocins for maintenance of milk quality were lacking. In the present study, a novel bacteriocin RSQ01 of Lactococcus lactis was purified and characterized extensively. The RSQ01 possessed a molecular weight of 1.90 kDa and an amino acid sequence of GTPSGGADGIGFAFHPEEVG, which exhibited an extensive antimicrobial spectrum against both gram-positive and gram-negative bacteria. Moreover, RSQ01 exhibited excellent tolerance to heat and acid-base treatments, and sensitivity to the proteolytic enzymes, such as trypsin, proteinase K, and pepsin, with a MIC value of 11.63 μg/mL against S. Enteritidis_35. Furthermore, RSQ01 maintained the nutritional composition, antioxidant parameters, and sensory properties of milk. Additionally, 238 differentially abundant metabolites (DAMs) were identified between the RSQ01-treated and -free milk by global metabolomics, which were assigned to eight categories/superclasses (e.g., organic acids and derivatives, lipids and lipid-like molecules, and organoheterocyclic compound). Finally, fourteen metabolic pathways enriched by DAMs were primarily involved in amino acid, lipids, and organic acid metabolism (e.g., phenylalanine/pyrimidine/tryptophan metabolism, glycerophospholipid metabolism, and C5-branched dibasic acid metabolism). The results provide evidence suggesting that abundance changes in metabolomes caused by RSQ01 contributed to the milk quality. Overall, this study indicated potential of RSQ01 in milk preservation.

Effects of Atractylodes lancea extracts on intestinal flora and serum metabolites in mice with intestinal dysbacteriosis

ObjectiveThis study aims to explore the effect of an extract of Atractylodes lancea (A. lancea) on antibiotics-induced intestinal tract disorder and the probable therapeutic mechanisms employed by this extract to ameliorate these disorders.MethodsThree days after acclimatization, nine male and nine female specific-pathogen-free (SPF) mice were randomly assigned into three groups: Group C (normal saline), Group M (antibiotic: cefradine + gentamicin), and Group T (antibiotic + A. lancea extract). Each mouse in Groups M and T received intragastric (i.g.) gavage antibiotics containing cefradine and gentamicin sulfate (0.02 ml/g−1/D−1) for 7 days. A. lancea extract (0.02 ml/g−1/D−1) was administered by i.g. gavage to Group T mice for 7 days following the cessation of antibiotic therapy. Group M received an equivalent volume of normal saline for 7 days, while Group C received an equivalent volume of normal saline for 14 days. Afterwards, we collected mouse feces to assess changes in intestinal microbiota by 16S ribosomal ribonucleic acid (rRNA) sequencing and metabolomics. In addition, serum samples were gathered and analyzed using liquid chromatography–mass spectrometry (LS-MS). Finally, we performed a correlation analysis between intestinal microbiota and metabolites.ResultsAfter treatment with antibiotic, the richness and diversity of the flora, numbers of wall-breaking bacteria and Bacteroidetes, and the numbers of beneficial bacteria decreased, while the numbers of harmful bacteria increased. After i.g. administration of A. lancea extract, the imbalance of microbial flora began to recover. Antibiotics primarily influence the metabolism of lipids, steroids, peptides, organic acids, and carbohydrates, with lipid compounds ranking first. Arachidonic acid (AA), arginine, and proline have relatively strong effects on the metabolisms of antibiotic-stressed mice. Our findings revealed that A. lancea extract might restore the metabolism of AA and L-methionine. The content of differential metabolites detected in the serum of Group T mice was comparable to that in the serum of Group C mice, but significantly different from that of Group M mice. Compared to putative biomarkers in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, it was found that altered metabolites, such as amino acids, glycerol, and phospholipids, were primarily associated with the metabolism.ConclusionsThe effective mechanisms of A. lancea extract in regulating the disorder of intestinal flora in mice are related to the mechanisms of A. lancea. It could relate to lipid metabolism, bile acid metabolism, and amino acid metabolism. These results will provide a basis for further explaining the mechanism by which A. lancea regulats intestinal flora.

Serum metabolic alterations in peritoneal dialysis patients with excessive daytime sleepiness

Excessive daytime sleepiness (EDS) is associated with quality of life and all-cause mortality in the end-stage renal disease population. This study aims to identify biomarkers and reveal the underlying mechanisms of EDS in peritoneal dialysis (PD) patients. A total of 48 nondiabetic continuous ambulatory peritoneal dialysis patients were assigned to the EDS group and the non-EDS group according to the Epworth Sleepiness Scale (ESS). Ultra-high-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) was used to identify the differential metabolites. Twenty-seven (male/female, 15/12; age, 60.1 ± 16.2 years) PD patients with ESS ≥ 10 were assigned to the EDS group, while twenty-one (male/female, 13/8; age, 57.9 ± 10.1 years) PD patients with ESS < 10 were defined as the non-EDS group. With UHPLC-Q-TOF/MS, 39 metabolites with significant differences between the two groups were found, 9 of which had good correlations with disease severity and were further classified into amino acid, lipid and organic acid metabolism. A total of 103 overlapping target proteins of the differential metabolites and EDS were found. Then, the EDS–metabolite–target network and the protein–protein interaction network were constructed. The metabolomics approach integrated with network pharmacology provides new insights into the early diagnosis and mechanisms of EDS in PD patients.

Component and microbial community structure change of Huangjiu undergoing rancidification during pottery jar storage

ABSTRACT The effects of microbial contamination on the rancidity of Huangjiu (Chinese rice wine) during pottery jar storage were studied. With the increase in the rancidity of Huangjiu, the alcohol content decreased, while the conductivity increased significantly. The sour taste and umami taste of Huangjiu increased, leading to flavor deterioration. Meanwhile, the increase in biogenic amine content makes Huangjiu unfit for drinking. The changes in components showed that the degree of rancidity was related to the metabolism of organic acids and amino acids caused by contaminated microorganisms. According to the analysis of microbial community structure, more microorganisms were found in the severe rancid Huangjiu. This indicated that with the aggravation of the degree of rancidity, the community structure of the contaminated microorganisms becomes complex, and potentially pathogenic microorganisms such as Arcobacter species were detected. Therefore, the change of components of Huangjiu will also affect the community structure of contaminated microorganisms.

Differential modulation of Target of Rapamycin activity undersingle and combined iron and sulfur deficiency in tomato plants.

Over the past few decades, a close relationship between sulfur (S) and iron (Fe) in terms of functionality and nutrition was demonstrated in the tomato. However, very little is known about the regulatory mechanisms underlying S/Fe interactions. Recently, the potential role of citrate in plant adaptation to Fe deficiency and combined S and Fe deficiency has been described. It is known that an impaired organic acid metabolism may stimulate a retrograde signal, which has been proven to be linked to the Target of Rapamycin (TOR) signaling in yeast and animal cells. Recent reports provided evidence of TOR involvement in S nutrient sensing in plants. This suggestion prompted us to investigate whether TOR may play a role in the cross-talk of signaling pathway occurring during plant adaptation to combined nutrient deficiency of Fe and S. Our results revealed that Fe deficiency elicited an increase of TOR activity associated with enhanced accumulation of citrate. In contrast, S deficiency resulted in decreased TOR activity and citrate accumulation. Interestingly, citrate accumulated in shoots of plants exposed to combined S/Fe deficiency to values between those found in Fe- and S-deficient plants, again correlated with TOR activity level. Our results suggest that citrate might be involved in establishing a link between plant response to combined S/Fe deficiency and the TOR network.

New insight into phytometabolism and phytotoxicity mechanism of widespread plasticizer di (2-ethylhexyl) phthalate in rice plants

Di-(2-ethylhexyl) phthalate (DEHP) as widely utilized plasticizer has aroused increasing concerns since its endocrine disrupting effects and continuous accumulation in biota. To date, the interaction mechanism between DEHP and rice plants has not been clearly illustrated at molecular level. Here, we investigated biological transformation and response of rice plants (Oryza sativa L.) to DEHP at realistic exposure concentrations. Nontargeted screening by UPLC-QTOF-MS was used to verify 21 transformation products derived from phase I metabolism (hydroxylation and hydrolysis) and phase II metabolism (conjugation with amino acids, glutathione, and carbohydrates) in rice. MEHHP-asp, MEHHP-tyr, MEHHP-ala, MECPP-tyr and MEOHP-tyr as the conjugation products with amino acids are observed for the first time. Transcriptomics analyses unraveled that DEHP exposure had strong negative effects on genes associated with antioxidative components synthesis, DNA binding, nucleotide excision repair, intracellular homeostasis, and anabolism. Untargeted metabolomics revealed that metabolic network reprogramming in rice roots was induced by DEHP, including nucleotide metabolism, carbohydrate metabolism, amino acid synthesis, lipid metabolism, synthesis of antioxidant component, organic acid metabolism and phenylpropanoid biosynthesis. The integrated analyses of interaction between differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) endorsed that metabolic network regulated by DEGs was significantly interfered by DEHP, resulting in cell dysfunction of roots and visible growth inhibition. Overall, these finding generated fresh perspective for crops security caused by plasticizer pollution and enhanced the public focus on dietary risk.

GABA shunt pathway is stimulated in response to early defoliation-induced carbohydrate limitation in Mandarin fruits

The regulation of sugar and organic acid metabolism during fruit development has a major effect on high-quality fruit production. The reduction of leaf area is a common feature in plant growth, induced by abiotic and biotic stresses and disturbing source/sink ratio, thus impacting fruit quality. Here, we induced carbohydrate limitation by partial leaf defoliation at the beginning of the second stage of mandarin development (before the citrate peak). Resulting changes were monitored in the short-term (48 h and 1 week) and long-term (7 weeks) after the defoliation. Short-term response to early defoliation implied metabolic settings to re-feed TCA for sustaining respiration rate. These features involved (i) vacuolar sucrose degradation (high acid invertase activity and mRNA expression level) and enhanced glycolytic flux (high ATP-phosphofructokinase activity), (ii) malic and citric acid utilization (increased phosphoenolpyruvate kinase and NADP-Isocitrate dehydrogenase) associated with vacuolar citric acid release (high mRNA expression of the transporter CsCit1) and (iii) stimulation of GABA shunt pathway (low GABA content and increased mRNA expression of succinate semialdehyde dehydrogenase). A steady-state proline level was found in ED fruits although an increase in P5CS mRNA expression level. These results contribute to a better knowledge of the molecular basis of the relationship between defoliation and sugar and organic acid metabolism in mandarin fruit.

Inhibitory effect of ε-poly-L-lysine on fruit Colletotrichum gloeosporioides through regulating organic acid metabolism and exerting membrane-targeted antifungal activity

Colletotrichum gloeosporioides (C. gloeosporioides) is the eighth harmful fungus among the top ten fungal pathogens in plant pathology, and the anthrax is a highly infectious disease caused by it. More efficient and environmental-friendly biological fungicide is needed to control anthrax. This study analyzed the inhibition mechanism of ε-poly-L-lysine (ε-PL) on C. gloeosporioides from the perspective of organic acid metabolism and membrane targeting. The results showed that ε-PL had a better inhibitory effect on C. gloeosporioides in vitro than commonly used chlorine source fungicides, such as chlorine dioxide and sodium hypochlorite. In vivo study, it was found that ε-PL reduced the expansion of anthracnose in winter jujube, fig, mango, tomato, apple and pitaya fruit. In addition, ε-PL had a remarkable impact on spore germination, germ tube elongation, mycelia morphology，and hypha density of C. gloeosporioides. From aspect of membrane targeting, ε-PL treatment destroyed the cell membrane of C. gloeosporioides, causing leakage of cell contents, lipid peroxidation of cell membrane and damage of mitochondria. In addition, from the results of pH and total acid determination, the pH of the control group decreased from 5.72 to 4.71, and the total acid content increased by 8.4 g L−1. High-Performance Liquid Chromatography (HPLC) results showed that C. gloeosporioides mainly producing malic acid, and its content accounted for 58.46% of the total organic acid, followed by citric acid, lactic acid and succinic acid. After 96 h of culture, the contents of four acids in 400 mg L−1 group were inhibited by 71.50%, 6.25%, 14.71% and 100% respectively, compared with the control group. The above results showed that ε-PL could play a remarkable antifungal role by causing membrane damage of C. gloeosporioides and regulating the organic acid metabolism.

Integrating Metabolomics and Proteomics Technologies Provides Insights into the Flavor Precursor Changes at Different Maturity Stages of Arabica Coffee Cherries.

The metabolic modulation of major flavor precursors during coffee cherry ripening is critical for the characteristic coffee flavor formation. However, the formation mechanism of flavor precursors during coffee cherry ripening remains unknown. In the present study, a colorimeter was employed to distinguish different maturity stages of coffee cherry based on the coffee cherry skin colors, and proteomics and metabolomics profiles were integrated to comprehensively investigate the flavor precursor dynamics involved in Arabica coffee cherry ripening. The data obtained in the present study provide an integral view of the critical pathways involved in flavor precursor changes during coffee cherry ripening. Moreover, the contributions of critical events in regulating the development of flavor precursors during the four ripening stages of coffee cherries, including the biosynthesis and metabolism pathways of organic acids, amino acids, flavonoids, and sugars, are discussed. Overall, a total of 456 difference express metabolites were selected, and they were identified as being concentrated in the four maturity stages of coffee cherries; furthermore, 76 crucial enzymes from the biosynthesis and metabolism of sugars, organic acids, amino acids, and flavonoids contributed to flavor precursor formation. Among these enzymes, 45 difference express proteins that could regulate 40 primary amino acids and organic acids flavor precursors were confirmed. This confirmation indicates that the metabolic pathways of amino acids and organic acids played a significant role in the flavor formation of Arabica coffee cherries during ripening. These results provide new insights into the protease modulation of flavor precursor changes in Arabica coffee cherry ripening.

Pre-storage temperature conditioning reduces cortex browning and cavity and alters organic, amino, and fatty acid metabolism in cold-stored ‘Chuhwangbae’ pears

‘Chuhwangbae’ pears are susceptible to internal disorders thought to be related to abiotic physiological chilling stress during cold storage. For this cultivar, pre-storage warm temperature conditioning (e.g. gradual or step-down of fruit temperatures) after harvest is highly recommended to control the development of postharvest storage disorders during cold storage. This pre-storage temperature conditioning at relatively warm temperatures relative to final storage temperature is also called “ambient temperature” conditioning by fruit packinghouse personnel. This study evaluated the influence of pre-storage ambient temperature conditioning duration (holding fruit at 22 °C) on ‘Chuhwangbae’ pear fruit quality including the incidence of physiological disorders and metabolic responses related to these disorders during cold storage. Postharvest pre-storage temperature conditioning (1, 2, 3, or 4 weeks at 22 °C) reduced cortex lightness and flesh firmness, and increased fruit weight loss and shrivelling during cold storage. The incidence and severity of cortex browning and cavity were reduced by pre-storage temperature conditioning. Pre-storage temperature conditioning reduced glucose, sorbitol, and fumaric acid contents after cold storage. Phenylalanine, isoleucine, and valine contents decreased with pre-storage temperature conditioning, but methionine, glutamine, and proline contents were higher in conditioned fruit than in unconditioned fruit. In addition, oleic acid content and the ratio of unsaturated fatty acid to saturated fatty acid were reduced by pre-storage temperature conditioning during cold storage. Results indicate that pre-storage temperature conditioning reduces incidence of cortex browning and cavity in part by altering cell wall metabolism during cold storage. Concurrently, pre-storage temperature conditioning reduces metabolites that are substrates for primary metabolism (glucose, sorbitol, and fumaric acid) and for volatile metabolism (isoleucine and valine), which corresponded to other aspects of fruit quality negatively affected by pre-storage temperature conditioning.