The metabolomics of oxidative stress

Procyanidin B2 improves developmental capacity of bovine oocytes via promoting PPARγ/UCP1-mediated uncoupling lipid catabolism during in vitro maturation

Metabolic balance is essential for oocyte maturation and acquisition of developmental capacity. Suboptimal conditions of in vitro cultures would lead to lipid accumulation and finally result in disrupted oocyte metabolism. However, the effect and mechanism underlying lipid catabolism in oocyte development remain elusive currently. In the present study, we observed enhanced developmental capacity in Procyanidin B2 (PCB2) treated oocytes during in vitro maturation. Meanwhile, reduced oxidative stress and declined apoptosis were found in oocytes after PCB2 treatment. Further studies confirmed that oocytes treated with PCB2 preferred to lipids catabolism, leading to a notable decrease in lipid accumulation. Subsequent analyses revealed that mitochondrial uncoupling was involved in lipid catabolism, and suppression of uncoupling protein 1 (UCP1) would abrogate the elevated lipid consumption mediated by PCB2. Notably, we identified peroxisome proliferator-activated receptor gamma (PPARγ) as a potential target of PCB2 by docking analysis. Subsequent mechanistic studies revealed that PCB2 improved oocyte development capacity and attenuated oxidative stress by activating PPARγ mediated mitochondrial uncoupling. Our findings identify that PCB2 intricately improves oocyte development capacity through targeted activation of the PPARγ/UCP1 pathway, fostering uncoupling lipid catabolism while concurrently mitigating oxidative stress.

Nanomaterials in plant physiology: Main effects in normal and under temperature stress

Global climate change and high population growth rates lead to problems of food security and environmental pollution, which require new effective methods to increase yields and stress tolerance of important crops. Nowadays the question of using artificial chemicals is very relevant in theoretical and practical terms. It is important that such substances in low concentrations protect plants under stress conditions, but at the same time inflict minimal damage on the environment and human health. Nanotechnology, which allows the production of a wide range of nanomaterials (NM), provides novel techniques in this direction. NM include structures less than 100 nm. The review presents data on the methods of NM production, their properties, pathways for arrival in plants and their use in human life. It is shown that NM, due to their unique physical and chemical properties, can cross biological barriers and accumulate in cells of live organisms. The influence of NM on plant organism can be both positive and negative, depending on the NM chemical nature, their size and dose, the object of study, and the environmental conditions. This review provides a comparative analysis of the effect of artificial metal nanoparticles (NPm), the commonly employed NMs in plant physiology, on two important aspects of plant life: photosynthetic apparatus activity and antioxidant system function. According to studies, NM affect not only the functional activity of photosynthetic apparatus, but also structural organization of chloroplats. In addition, the literature analysis reflects the dual action of NM on oxidative processes, and antioxidant status of plants. These facts considerably complicate the ideas about possible mechanisms and further use of NPm in biology. In this regard, data on the effects of NM on plants under abiotic stressors are of great interest. Separate section is devoted to the use of NM as adaptogens that increase plant stress tolerance to unfavorable temperatures. Possible mechanisms of NM effects on plants are discussed, as well as the strategies for their further use in basic science and sustainable agriculture.

Genome-wide profiling of DNA methylome and transcriptome reveals epigenetic regulation of Urechis unicinctus response to sulfide stress

Sulfide is a well-known environmental pollutant that can have detrimental effects on most organisms. However, few metazoans living in sulfide-rich environments have developed mechanisms to tolerate and adapt to sulfide stress. Epigenetic mechanisms, including DNA methylation, have been shown to play a vital role in environmental stress adaptation. Nevertheless, the precise function of DNA methylation in biological sulfide adaptation remains unclear. Urechis unicinctus, a benthic organism inhabiting sulfide-rich intertidal environments, is an ideal model organism for studying adaptation to sulfide environments. In this study, we conducted a comprehensive analysis of the DNA methylome and transcriptome of U. unicinctus after exposure to 50 μM sulfide. The results revealed dynamic changes in the DNA methylation (5-methylcytosine) landscape in response to sulfide stress, with U. unicinctus exhibiting elevated DNA methylation levels following stress exposure. Integrating differentially expressed genes (DEGs) and differentially methylated regions (DMRs), we identified a crucial role of gene body methylation in predicting gene expression. Furthermore, using a DNA methyltransferase inhibitor, we validated the involvement of DNA methylation in the sulfide stress response and the gene regulatory network influenced by DNA methylation. The results indicated that by modulating DNA methylation levels during sulfide stress, the expression of glutathione S-transferase, glutamyl aminopeptidase, and cytochrome c oxidase could be up-regulated, thereby facilitating the metabolism and detoxification of exogenous sulfides. Moreover, DNA methylation was found to regulate and enhance the oxidative phosphorylation pathway, including NADH dehydrogenase, isocitrate dehydrogenase, and ATP synthase. Additionally, DNA methylation influenced the regulation of Cytochrome P450 and macrophage migration inhibitory factor, both of which are closely associated with oxidative stress and stress resistance. Our findings not only emphasize the role of DNA methylation in sulfide adaptation but also provide novel insights into the potential mechanisms through which marine organisms adapt to environmental changes.

Salicylic acid foliar application meliorates Portulaca oleraceae L. growth responses under Pb and Ni over-availability while keeping reliable phytoremediation potential

The efficacy of SA foliar use on Pb and Ni-induced stress tolerance and phytoremediation potential by Portulaca oleraceae L. were assayed as a factorial trial based on a completely randomized design with four repetitions. The factors included; SA foliar application (0 and 100 µM) and HMs application of Pb [0, 150, and 225 mg kg-1 soil Lead (II) nitrate] and Ni [0, 220, and 330 mg kg-1 soil Nickel (II) nitrate]. Plant height, stem diameter, shoot and root fresh and dry weight, photosynthetic pigments, total soluble proteins, palmitic acid, stearic acid, arachidic acid, and some macro- and micro-elements contents were reduced facing the HMs stress, but SA foliar application ameliorated these traits. HMs stress increased malondialdehyde content, total antioxidant activity, total flavonoids, phenolics, and linolenic acid content, while SA foliar application declined the mentioned parameters. Moreover, shoot and root Pb and Ni content enhanced in the purslane plants supplemented by SA under the HMs stress. The results propose SA foliar application as a reliable methodology to recover purslane growth characters and fatty acid profiles in the soil contaminated with the HMs. The idea is that SA would be potentially effective in alleviating HMs contamination while keeping reasonable phytoremediation potential.

Enhancing systematic tolerance in Bermuda grass (Cynodon dactylon L.) through amplified alkB gene expression and bacterial-driven hydrocarbon degradation

This study aimed to access the impact of soil polluted with petroleum (5, 10 g petroleum kg-1 soil) on Bermuda grass (Cynodon dactylon L.) with and without applied bacterial inoculants (Arthrobacter oxydans ITRH49 and Pseudomonas sp. MixRI75). Both soil and seed were given bacterial inoculation. The evaluated morphological parameters of Bermuda grass were fresh and dry weight. The results demonstrated that applied bacterial inoculants enhanced 5.4%, 20%, 28% and 6.4%, 21%, and 29% shoot and root fresh/dry weights in Bermuda grass under controlled environment. The biochemical analysis of shoot and root was affected deleteriously by the 10 g petroleum kg-1 soil pollution. Microbial inoculants enhanced the activities of enzymatic (catalase, peroxidase, glutathione reductase, ascorbate peroxidase, superoxide dismutase) and non-enzymatic (ɑ-tocopherols, proline, reduced glutathione, ascorbic acid) antioxidant to mitigate the toxic effects of ROS (H2O2) under hydrocarbon stressed condition. The maximum hydrocarbon degradation (75%) was recorded by Bermuda grass at 5 g petroleum kg-1 soil contamination. Moreover, bacterial persistence and alkane hydroxylase gene (alkB) abundance and expression were observed more in the root interior than in the rhizosphere and shoot interior of Bermuda grass. Subsequently, the microbe used a biological tool to propose that the application of plant growth-promoting bacteria would be the most favorable choice in petroleum hydrocarbon polluted soil to conquer the abiotic stress in plants and the effective removal of polyaromatic hydrocarbons in polluted soil.

Sequential removal of cation/H+ exchangers reveals their additive role in elemental distribution, calcium depletion and anoxia tolerance

Multiple Arabidopsis H+ /Cation exchangers (CAXs) participate in high-capacity transport into the vacuole. Previous studies have analysed single and double mutants that marginally reduced transport; however, assessing phenotypes caused by transport loss has proven enigmatic. Here, we generated quadruple mutants (cax1-4: qKO) that exhibited growth inhibition, an 85% reduction in tonoplast-localised H+ /Ca transport, and enhanced tolerance to anoxic conditions compared to CAX1 mutants. Leveraging inductively coupled plasma mass spectrometry (ICP-MS) and synchrotron X-ray fluorescence (SXRF), we demonstrate CAX transporters work together to regulate leaf elemental content: ICP-MS analysis showed that the elemental concentrations in leaves strongly correlated with the number of CAX mutations; SXRF imaging showed changes in element partitioning not present in single CAX mutants and qKO had a 40% reduction in calcium (Ca) abundance. Reduced endogenous Ca may promote anoxia tolerance; wild-type plants grown in Ca-limited conditions were anoxia tolerant. Sequential reduction of CAXs increased mRNA expression and protein abundance changes associated with reactive oxygen species and stress signalling pathways. Multiple CAXs participate in postanoxia recovery as their concerted removal heightened changes in postanoxia Ca signalling. This work showcases the integrated and diverse function of H+ /Cation transporters and demonstrates the ability to improve anoxia tolerance through diminishing endogenous Ca levels.

H2O2 Significantly Affects Larix kaempferi × Larix olgensis Somatic Embryogenesis

Larch is widely distributed throughout the world and is an important species for timber supply and the extraction of industrial raw materials. In recent years, the hybrid breeding of Larix kaempferi and Larix olgensis has shown obvious heterosis in quick-growth, stress resistance and wood properties. However, its growth and development cycle is too long to meet general production needs. In order to shorten the breeding cycle, we have for the first time successfully established and optimized a somatic embryogenesis system for Larix kaempferi × Larix olgensis. We found that the highest rate of embryonal-suspensor mass (ESM) induction was observed when late cotyledonary embryos were used as explants. The induced ESMs were subjected to stable proliferation, after which abscisic acid (ABA) and polyethylene glycol (PEG) were added to successfully induce somatic embryos. Treatment with PEG and ABA was of great importance to somatic embryo formation and complemented each other's effect. ABA assisted embryo growth, whereas PEG facilitated the formation of proembryo-like structures. On top of this, we studied in more detail the relationship between redox homeostasis and the efficiency of somatic embryogenesis (frequency of ESM induction). During subculture, we observed the gradual formation of three distinct types of ESM. The Type I ESM is readily able to form somatic embryos. In contrast to type I, the type III ESM suffers from severe browning, contains a higher level of hydrogen peroxide (H2O2) and demonstrates a decreased ability to form somatic embryos. External treatment with H2O2 decreased the somatic embryogenesis efficiency of Type I and type III ESMs, or the higher the exogenous H2O2 content, the lower the resulting somatic embryogenesis efficiency. We found that treatment with the H2O2 scavenger DMTU (dimethylthiourea) could significantly increase the somatic embryogenesis efficiency of the type III ESM, as a result of a decline in endogenous H2O2 content. Overall, these findings have contributed to setting up a successful somatic embryogenesis system for larch production.

The nitrate transporter-sensor MtNPF6.8 regulates the branched chain amino acid/pantothenate metabolic pathway in barrel medic (Medicago truncatula Gaertn.) root tip

Nitrogen is the most limiting nutrient for plants, and it is preferentially absorbed in the form of nitrate by roots, which adapt to nitrate fluctuations by remodelling their architecture. Although core mechanisms of the response to nitrate availability are relatively well-known, signalling events controlling root growth and architecture have not all been identified, in particular in Legumes. However, the developmental effect of nitrate in Legumes is critical since external nitrate not only regulates root architecture but also N2-fixing nodule development. We have previously shown that in barrel medic (Medicago truncatula), the nitrate transporter MtNPF6.8 is required for nitrate sensitivity in root tip. However, uncertainty remains as to whether nitrogen metabolism itself is involved in the MtNPF6.8-mediated response. Here, we examine the metabolic effects of MtNPF6.8-dependent nitrate signalling using metabolomics and proteomics in WT and mtnpf6.8 root tips in presence or absence of nitrate. We found a reorchestration of metabolism due to the mutation, in favour of the branched chain amino acids/pantothenate metabolic pathway, and lipid catabolism via glyoxylate. That is, the mtnpf6.8 mutation was likely associated with a specific rerouting of acetyl-CoA production (glyoxylic cycle) and utilisation (pantothenate and branched chain amino acid synthesis). In agreement with our previous findings, class III peroxidases were confirmed as the main protein class responsive to nitrate, although in an MtNPF6.8-independent fashion. Our data rather suggest the involvement of other pathways within mtnpf6.8 root tips, such as Ca2+ signalling or cell wall methylation.

The ERF transcription factor LTF1 activates DIR1 to control stereoselective synthesis of antiviral lignans and stress defense in Isatis indigotica roots

Lignans are a powerful weapon for plants to resist stresses and have diverse bioactive functions to protect human health. Elucidating the mechanisms of stereoselective biosynthesis and response to stresses of lignans is important for the guidance of plant improvement. Here, we identified the complete pathway to stereoselectively synthesize antiviral (-)-lariciresinol glucosides in Isatis indigotica roots, which consists of three-step sequential stereoselective enzymes DIR1/2, PLR, and UGT71B2. DIR1 was further identified as the key gene in respoJanuary 2024nse to stresses and was able to trigger stress defenses by mediating the elevation in lignan content. Mechanistically, the phytohormone-responsive ERF transcription factor LTF1 colocalized with DIR1 in the cell periphery of the vascular regions in mature roots and helped resist biotic and abiotic stresses by directly regulating the expression of DIR1. These systematic results suggest that DIR1 as the first common step of the lignan pathway cooperates with PLR and UGT71B2 to stereoselectively synthesize (-)-lariciresinol derived antiviral lignans in I. indigotica roots and is also a part of the LTF1-mediated regulatory network to resist stresses. In conclusion, the LTF1-DIR1 module is an ideal engineering target to improve plant Defenses while increasing the content of valuable lignans in plants.

Traffic Density Exposure, Oxidative Stress Biomarkers and Plasma Metabolomics in a Population-Based Sample: The Hortega Study

Exposure to traffic-related air pollution (TRAP) generates oxidative stress, with downstream effects at the metabolic level. Human studies of traffic density and metabolomic markers, however, are rare. The main objective of this study was to evaluate the cross-sectional association between traffic density in the street of residence with oxidative stress and metabolomic profiles measured in a population-based sample from Spain. We also explored in silico the potential biological implications of the findings. Secondarily, we assessed the contribution of oxidative stress to the association between exposure to traffic density and variation in plasma metabolite levels. Traffic density was defined as the average daily traffic volume over an entire year within a buffer of 50 m around the participants' residence. Plasma metabolomic profiles and urine oxidative stress biomarkers were measured in samples from 1181 Hortega Study participants by nuclear magnetic resonance spectroscopy and high-performance liquid chromatography, respectively. Traffic density was associated with 7 (out of 49) plasma metabolites, including amino acids, fatty acids, products of bacterial and energy metabolism and fluid balance metabolites. Regarding urine oxidative stress biomarkers, traffic associations were positive for GSSG/GSH% and negative for MDA. A total of 12 KEGG pathways were linked to traffic-related metabolites. In a protein network from genes included in over-represented pathways and 63 redox-related candidate genes, we observed relevant proteins from the glutathione cycle. GSSG/GSH% and MDA accounted for 14.6% and 12.2% of changes in isobutyrate and the CH2CH2CO fatty acid moiety, respectively, which is attributable to traffic exposure. At the population level, exposure to traffic density was associated with specific urine oxidative stress and plasma metabolites. Although our results support a role of oxidative stress as a biological intermediary of traffic-related metabolic alterations, with potential implications for the co-bacterial and lipid metabolism, additional mechanistic and prospective studies are needed to confirm our findings.

Plant Life with and without Oxygen: A Metabolomics Approach

Oxygen deficiency is an environmental challenge which affects plant growth, the development and distribution in land and aquatic ecosystems, as well as crop yield losses worldwide. The capacity to exist in the conditions of deficiency or the complete lack of oxygen depends on a number of anatomic, developmental and molecular adaptations. The lack of molecular oxygen leads to an inhibition of aerobic respiration, which causes energy starvation and the acceleration of glycolysis passing into fermentations. We focus on systemic metabolic alterations revealed with the different approaches of metabolomics. Oxygen deprivation stimulates the accumulation of glucose, pyruvate and lactate, indicating the acceleration of the sugar metabolism, glycolysis and lactic fermentation, respectively. Among the Krebs-cycle metabolites, only the succinate level increases. Amino acids related to glycolysis, including the phosphoglycerate family (Ser and Gly), shikimate family (Phe, Tyr and Trp) and pyruvate family (Ala, Leu and Val), are greatly elevated. Members of the Asp family (Asn, Lys, Met, Thr and Ile), as well as the Glu family (Glu, Pro, Arg and GABA), accumulate as well. These metabolites are important members of the metabolic signature of oxygen deficiency in plants, linking glycolysis with an altered Krebs cycle and allowing alternative pathways of NAD(P)H reoxidation to avoid the excessive accumulation of toxic fermentation products (lactate, acetaldehyde, ethanol). Reoxygenation induces the downregulation of the levels of major anaerobically induced metabolites, including lactate, succinate and amino acids, especially members of the pyruvate family (Ala, Leu and Val), Tyr and Glu family (GABA and Glu) and Asp family (Asn, Met, Thr and Ile). The metabolic profiles during native and environmental hypoxia are rather similar, consisting in the accumulation of fermentation products, succinate, fumarate and amino acids, particularly Ala, Gly and GABA. The most intriguing fact is that metabolic alterations during oxidative stress are very much similar, with plant response to oxygen deprivation but not to reoxygenation.

Oxidative Damage as a Fundament of Systemic Toxicities Induced by Cisplatin-The Crucial Limitation or Potential Therapeutic Target?

Cisplatin, an inorganic complex of platinum, is a chemotherapeutic drug that has been used for 45 years. Despite the progress of pharmaceutical sciences and medicine and the successful application of other platinum complexes for the same purpose, cisplatin is still the therapy of choice in many cancers. Treatment for testicular, ovarian, head and neck, urothelial, cervical, esophageal, breast, and pulmonary malignancies is still unthinkable without the use of this drug. However, cisplatin is also known for many side effects, of which the most pronounced are nephrotoxicity leading to acute renal failure, neurotoxicity, and ototoxicity. Mechanistic studies have proven that one of the conditions that plays a major role in the development of cisplatin-induced toxicities is oxidative stress. Knowing the fact that numerous antioxidants can be used to reduce oxidative stress, thereby reducing tissue lesions, organ failure, and apoptosis at the cellular level, many studies have defined antioxidants as a priority for investigation as a cotreatment. To investigate the mechanism of antioxidant action in vivo, many animal models have been employed. In the last few years, studies have mostly used rodents and zebrafish models. In this article, some of the most recent investigations that used animal models are listed, and the advantages and disadvantages of such experimental studies are pointed out.

Domestication shapes the endophytic microbiome and metabolome of Salicornia europaea

AIMS

We aim at understanding the effect of domestication on the endophytic microbiome and metabolome of Salicornia europaea and collecting evidence on the potential role of microbial populations and metabolites in the adaptation of plants to different ecological contexts (wild vs crops).

METHODS AND RESULTS

Samples were collected from a natural salt marsh (wild) and an intensive crop field (crop). High-throughput sequencing of the 16S rRNA gene, gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) were used to analyze the endophytic bacterial communities and the metabolite profiles of S. europaea roots, respectively. The elemental analysis of the plant shoots was performed by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS).Overall, significant differences were found between the microbiome of wild and cultivated plants. The later showed a higher relative abundance of the genera Erythrobacter, Rhodomicrobium, and Ilumatobacter than wild plants. The microbiome of wild plants was enriched in Marinobacter, Marixanthomonas, and Thalassospira. The metabolite profile of crop plants revealed higher amounts of saturated and non-saturated fatty acids and acylglycerols. In contrast, wild plants contained comparatively more carbohydrates and most macroelements (i.e. Na, K, Mg, and Ca).

CONCLUSIONS

There is a strong correlation between plant metabolites and the endosphere microbiome of S. europaea. In wild populations, plants were enriched in carbohydrates and the associated bacterial community was enriched in genes related to primary metabolic pathways such as nitrogen metabolism and carbon fixation. The endosphere microbiome of crop plants was predicted to have higher gene counts related to pathogenesis. Crop plants also exhibited higher amounts of azelaic acid, an indicator of exposure to phytopathogens.

OsRbohI Regulates Rice Growth and Development via Jasmonic Acid Signalling

Reactive oxygen species (ROS) are highly reactive molecules, generated by nicotinamide adenine dinucleotide phosphate oxidases encoded by respiratory burst oxidase homologs. The functions of the OsRbohs gene family in rice are diverse and poorly understood. OsRbohI was recently identified as a newly evolved gene in the rice OsRbohs gene family. However, the function of OsRbohI in regulating rice growth is not yet reported. In this study, our results indicate that knockout (KO) OsRbohI mutants showed significantly shorter shoot and primary roots, along with lower ROS content than the control lines, whereas the overexpression (OE) lines displayed contrasting results. Further experiments showed that the abnormal length of the shoot and root is mainly caused by altered cell size. These results indicate that OsRbohI regulates rice shoot and root growth through the ROS signal. More importantly, RNA-seq analysis and jasmonic acid (JA) treatment demonstrated that OsRbohI regulates rice growth via the JA synthesis and signaling pathways. Compared with the control, the results showed that the KO mutants were more sensitive to JA, whereas the OE lines were less sensitive to JA. Collectively, our results reveal a novel pathway in which OsRbohI regulates rice growth and development by affecting their ROS homeostasis through JA synthesis and signaling pathway.

Thioredoxins m regulate plastid glucose-6-phosphate dehydrogenase activity in Arabidopsis roots under salt stress

Plants contain several NADPH-producing enzymes including glucose-6-phosphate dehydrogenases (G6PDH) with different sub-cellular localizations. The activity of plastidial G6PDHs is redox-regulated by thioredoxins (TRX). Although specific TRXs are known to regulate chloroplastic isoforms of G6PDH, little information is available for plastidic isoforms found in heterotrophic organs or tissues. Here, we investigated TRX regulation of the two G6PDH plastidic isoforms of Arabidopsis roots during exposure to a mild salt stress. We report that in vitro m-type TRXs are the most efficient regulators of the G6PDH2 and G6PDH3 mainly found in Arabidopsis roots. While expression of the corresponding G6PD and plastidic TRX genes was marginally affected by salt, it impaired root growth of several of the corresponding mutant lines. Using an in situ assay for G6PDH, G6PDH2 was found to be the major contributor to salt-induced increases in activity, while data from ROS assays further provide in vivo evidence that TRX m acts in redox regulation during salt stress. Taken together, our data suggest that regulation of plastid G6PDH activity by TRX m may be an important player regulating NADPH production in Arabidopsis roots undergoing salt stress.

Aflatoxin B1 Degradation by Ery4 Laccase: From In Vitro to Contaminated Corn

Aflatoxins (AFs) are toxic secondary metabolites produced by Aspergillus spp. and are found in food and feed as contaminants worldwide. Due to climate change, AFs occurrence is expected to increase also in western Europe. Therefore, to ensure food and feed safety, it is mandatory to develop green technologies for AFs reduction in contaminated matrices. With this regard, enzymatic degradation is an effective and environmentally friendly approach under mild operational conditions and with minor impact on the food and feed matrix. In this work, Ery4 laccase, acetosyringone, ascorbic acid, and dehydroascorbic acid were investigated in vitro, then applied in artificially contaminated corn for AFB₁ reduction. AFB₁ (0.1 µg/mL) was completely removed in vitro and reduced by 26% in corn. Several degradation products were detected in vitro by UHPLC-HRMS and likely corresponded to AFQ₁, epi-AFQ₁, AFB₁-diol, or AFB₁dialehyde, AFB_2a, and AFM₁. Protein content was not altered by the enzymatic treatment, while slightly higher levels of lipid peroxidation and H₂O₂ were detected. Although further studies are needed to improve AFB₁ reduction and reduce the impact of this treatment in corn, the results of this study are promising and suggest that Ery4 laccase can be effectively applied for the reduction in AFB₁ in corn.

Effect of ascorbate and hydrogen peroxide on hormone and metabolite levels during post-germination growth in wheat

The modulation of hormone and metabolite levels by ascorbate (ASA) and hydrogen peroxide (H₂ O₂ ) was compared during post-germination growth in shoots of wheat. Treatment with ASA resulted in a greater reduction of growth than the addition of H₂ O₂ . ASA also had a larger effect on the redox state of the shoot tissues as shown by the higher ASA and glutathione (GSH) levels, lower glutathione disulfide (GSSG) content and GSSG/GSH ratio compared to the H₂ O₂ treatment. Apart from common responses (i.e., increase of cis-zeatin and its O-glucosides), the contents of several compounds related to cytokinin (CK) and abscisic acid (ABA) metabolism were greater after ASA application. These differences in the redox state and hormone metabolism following the two treatments may be responsible for their distinct influence on various metabolic pathways. Namely, the glycolysis and citrate cycle were inhibited by ASA and they were not affected by H₂ O₂ , while the amino acid metabolism was induced by ASA and repressed by H₂ O₂ based on the changes in the level of the related carbohydrates, organic and amino acids. The first two pathways produce reducing power, while the last one needs it; therefore ASA, as a reductant may suppress and induce them, respectively. H₂ O₂ as an oxidant had different effect, namely it did not alter glycolysis and citrate cycle, and inhibited the formation of amino acids.

Sinomenine promotes flap survival by upregulating eNOS and eNOS-mediated autophagy via PI3K/AKT pathway

Large skin defects and surgical tissue reconstructions are frequently covered utilizing random flaps. The flap has the advantage of being designed according to the size and shape of a surgical wound. However, the necrosis of the distal part of the flap restricts the clinical application of flaps. Sinomenine (SIN) is the major active component of sinomenium acutum. SIN has been demonstrated to inhibit oxidative stress and stimulate autophagy in a cell, animal, and clinical studies. The protective and proliferative effects of sinomenium on HUVECs were evaluated by scratched test, CCK-8, and EDU assays. For the flap survival, we established a mouse random pattern flap model and observed the effects of SIN injected intraperitoneally. The survival area and blood flow intensity of the flap in sinomenium group were significantly increased compared to the control group. Our results demonstrate that SIN promotes flap survival. Sinomenium enhances eNOS expression in the flap and reduces the level of oxidative stress, promotes autophagy flux increase, reduces apoptosis, and promotes angiogenesis. Having a therapeutic benefit of SIN, Autophagy inhibitor 3-MA shows its critical role by reversing the beneficial effects of SIN, and the nitric oxide synthase inhibitor l-NAME both stimulated HUVECs that explore the relationship between autophagy flux and nitric oxide synthase. Furthermore, the mechanism in our study reveals the changes in the signal pathway of PI3K/AKT, the protective effect of SIN during antioxidant activity, the activation of eNOS through PI3K/AKT signaling pathway affects autophagy through the eNOS system, and promote the random flap survival.

Metabolite modification in oxidative stress responses: A case study of two defense hormones

Studies of the Arabidopsis cat2 mutant lacking the major leaf isoform of catalase have allowed the potential impact of intracellular H₂O₂ on plant function to be studied. Here, we report a robust analysis of modified gene expression associated with key families involved in metabolite modification in cat2. Through a combined transcriptomic and metabolomic analysis focused on the salicylic acid (SA) and jasmonic acid (JA) pathways, we report key features of the metabolic signatures linked to oxidative stress-induced signaling via these defence hormones and discuss the enzymes that are likely to be involved in determining these features. We provide evidence that specific UDP-glycosyl transferases contribute to the glucosylation of SA that accumulates as a result of oxidative stress in cat2. Glycosides of dihydroxybenzoic acids that accumulate alongside SA in cat2 are identified and, based on the expression of candidate genes, likely routes for their production are discussed. We also report that enhanced intracellular H₂O₂ triggers induction of genes encoding different enzymes that can metabolize JA. Integrated analysis of metabolite and transcript profiles suggests that a gene network involving specific hydrolases, hydroxylases, and sulfotransferases functions to limit accumulation of the most active jasmonates during oxidative stress.

Manipulation in Culture Conditions of Nanofrustulum shiloi for Enhanced Fucoxanthin Production and Isolation by Preparative Chromatography

Microalgae produce a variety of high-value chemicals including carotenoids. Fucoxanthin is also a carotenoid that has many physiological functions and biological properties. For this reason, the cost-effective production of fucoxanthin at an industrial scale has gained significant attention. In the proposed study, fucoxanthin production was aimed to be increased by altering the culture conditions of N. shiloi. The effect of light intensity aeration rate, different nitrogen sources, and oxidative stress on the biomass and fucoxanthin productivity have been discussed. Based on these results, the fucoxanthin increased to 97.45 ± 2.64 mg/g by adjusting the light intensity to 50 µmol/m²s, and aeration rate at 5 L/min using oxidative stress through the addition of 0.1 mM H₂O₂ and 0.1 mM NaOCl to the culture medium. Fucoxanthin was then purified with preparative HPLC using C₃₀ carotenoid column (10 mm × 250 mm, 5 μm). After the purification procedure, Liquid chromatography tandem mass spectrometry (LC-MS/MS) and UV-vis spectroscopy were employed for the confirmation of fucoxanthin. This study presented a protocol for obtaining and purifying considerable amounts of biomass and fucoxanthin from diatom by manipulating culture conditions. With the developed methodology, N. shiloi could be evaluated as a promising source of fucoxanthin at the industrial scale for food, feed, cosmetic, and pharmaceutical industries.

Metabolomic Profile of Salicornia perennis Plant's Organs under Diverse In Situ Stress: The Ria de Aveiro Salt Marshes Case

Salicornia perennis is a halophyte belonging to the botanical subfamily Salicornioideae that forms extensive perennial salt marsh patches. This subfamily has excellent potential, still unexplored, as a source of food, medicine, and phytoremediation. This study aimed to evaluate the lipophilic composition of the Salicornia perennis different organs inhabiting salt marshes of Ria de Aveiro under different stress regimes. For this purpose, the lipophilic content was extracted with hexane and subsequent GC-MS analysis of the extracts for each plant organ, which was collected in three different salt marshes of the Ria de Aveiro. High sugar content was detected in the stems, whereas in fruiting articles, the higher content was in fatty acids. Shorter-chain organic acids were concentrated in the stems and vegetative articles; waxes were detected in greater quantity in photosynthetic organs. More or less stressful environments induce changes in the ratio and composition of molecules, such as acclimatization and oxidative stress reduction strategies; for example, fatty acid content was higher in plants subjected to a higher stress regime. These data contribute to understand the metabolic pathways of the species under study, suggesting new research approaches to its potential as food, medicine, and phytoremediator.

Cadmium contributes to heat tolerance of a hyperaccumulator plant species Sedum alfredii

Hyperaccumulators are plant species that tolerate and accumulate very high concentrations of toxic metals, including Cd. Hyperaccumulation of heavy metals is reported to benefit plant biotic resistance; however, no prior study has examined the possible role of toxic metals on abiotic stress resistance in hyperaccumulators. A preliminary experiment found that Cd significantly improved plant growth of a hyperaccumulator, Sedum alfredii Hance, under heat stress. This study investigated the possible role of Cd in S. alfredii's heat resistance, using infrared thermography, transmission electron microscopy (TEM), real-time quantitative polymerase chain reaction (RTqPCR), and high-throughput sequencing. The results showed that high temperatures irreversibly damaged stomatal function, chloroplast structure, photosynthesis in S. alfredii, and lowered survival rates to 25%. However, Cd application significantly decreased the leaf temperature of S. alfredii and increased the survival rate to 75%. Cd penetrated the guard cells, restored stomatal function, and mitigated excessive water loss from S. alfredii under heat stress. Moreover, it activated antioxidant enzymes, promoted phytohormone biosynthesis, and upregulated a series of unigenes, thereby augmenting heat resistance in S. alfredii. These results indicate that Cd effectively improved thermotolerance in S. alfredii by regulating stomatal movement and antioxidant systems via upregulation of phytohormones and heat shock proteins.

Proteome-wide analysis of hydrogen peroxide-induced protein carbonylation in Arabidopsis thaliana

INTRODUCTION

Protein carbonylation is a non-enzymatic and irreversible post-translational modification that occurs naturally in living organisms under the direct or indirect effect of reactive oxygen species (ROS). In animals, signaling pathways involving numerous carbonylated proteins have been identified, highlighting the dual role of these molecules in ROS signal transduction. In plants, studies on phytohormone signaling (auxin, methyl jasmonate, abscisic acid) have shown that reactive carbonyl species (RCS: acrolein, malondialdehyde, 4-hydroxynonenal, etc.), derived from the action of ROS on lipids, play important roles in secondary root formation and stomatal closure. However, the carbonylated proteins involved in these signaling pathways remain to be identified.

METHODS

In this study, we analyzed proteins responsive to carbonylation by exogenous hydrogen peroxide (H2O2) by profiling the carbonyl proteome extracted from Arabidopsis thaliana leaves after H2O2 treatment. Carbonylated proteins were enriched at the peptide level and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS).

RESULTS AND DISCUSSION

We identified 35 and 39 uniquely carbonylated proteins in the untreated and the H2O2-treated plant samples, respectively. In comparison to the control treatment, gene ontology enrichment analysis revealed that most of the carbonylated proteins identified in the H2O2-treated plant samples are related to sulfate adenylyl transferases and amidophosphoribosyl transferases involved in the immune system response, defense response, and external stimulus-response. These results indicated that exogenous H2O2 caused a change in the pattern of protein carbonylation in A. thaliana leaves. Protein carbonylation may thus influence the plant transcriptome and metabolism in response to H2O2 and ROS-triggering external stimuli.

Effects of inflammation and oxidative stress on postoperative delirium in cardiac surgery

The past decade has witnessed unprecedented medical progress, which has translated into cardiac surgery being increasingly common and safe. However, complications such as postoperative delirium remain a major concern. Although the pathophysiological changes of delirium after cardiac surgery remain poorly understood, it is widely thought that inflammation and oxidative stress may be potential triggers of delirium. The development of delirium following cardiac surgery is associated with perioperative risk factors. Multiple interventions are being explored to prevent and treat delirium. Therefore, research on the potential role of biomarkers in delirium as well as identification of perioperative risk factors and pharmacological interventions are necessary to mitigate the development of delirium.

Single, but not dual, attack by a biotrophic pathogen and a sap-sucking insect affects the oak leaf metabolome

Plants interact with a multitude of microorganisms and insects, both below- and above ground, which might influence plant metabolism. Despite this, we lack knowledge of the impact of natural soil communities and multiple aboveground attackers on the metabolic responses of plants, and whether plant metabolic responses to single attack can predict responses to dual attack. We used untargeted metabolic fingerprinting (gas chromatography-mass spectrometry, GC-MS) on leaves of the pedunculate oak, Quercus robur, to assess the metabolic response to different soil microbiomes and aboveground single and dual attack by oak powdery mildew (Erysiphe alphitoides) and the common oak aphid (Tuberculatus annulatus). Distinct soil microbiomes were not associated with differences in the metabolic profile of oak seedling leaves. Single attacks by aphids or mildew had pronounced but different effects on the oak leaf metabolome, but we detected no difference between the metabolomes of healthy seedlings and seedlings attacked by both aphids and powdery mildew. Our findings show that aboveground attackers can have species-specific and non-additive effects on the leaf metabolome of oak. The lack of a metabolic signature detected by GC-MS upon dual attack might suggest the existence of a potential negative feedback, and highlights the importance of considering the impacts of multiple attackers to gain mechanistic insights into the ecology and evolution of species interactions and the structure of plant-associated communities, as well as for the development of sustainable strategies to control agricultural pests and diseases and plant breeding.

Gold nanoparticles as adaptogens increazing the freezing tolerance of wheat seedlings

The intensive development of nanotechnology led to the widespread application of various nanoparticles and nanomaterials. As a result, nanoparticles enter the environment and accumulate in ecosystems and living organisms. The consequences of possible impact of nanoparticles on living organisms are not obvious. Experimental data indicate that nanoparticles have both toxic and stimulating effects on organisms. In this study, we demonstrated for the first time that gold nanoparticles can act as adaptogens increasing plant freezing tolerance. Priming winter wheat (Triticum aestivum L., var. Moskovskaya 39, Poaceae) seeds for 1 day in solutions of gold nanoparticles (15-nm diameter, concentrations of 5, 10, 20, and 50 µg/ml) led to an increase in freezing tolerance of 7-day-old wheat seedlings. A relationship between an increase in wheat freezing tolerance and changes in some important indicators for its formation-growth intensity, the activity of the photosynthetic apparatus and oxidative processes, and the accumulation of soluble sugars in seedlings-was established. Assumptions on possible mechanisms of gold nanoparticles effects on plant freezing tolerance are discussed.

Low Temperature Plasma Strategies for Xylella fastidiosa Inactivation

The quarantine bacterium Xylella fastidiosa was first detected in Salento (Apulia, Italy) in 2013 and caused severe symptoms in olives, leading to plant death. The disease, named Olive Quick Decline Syndrome (OQDS), is caused by the strain “De Donno” ST53 of the subspecies pauca of this bacterium (XfDD), which is spread by the insect Philaenus spumarius. The epidemic poses a serious threat to the agricultural economy and the landscape, as X. fastidiosa infects several plant species and there is yet no recognized solution. Research on OQDS is focused on finding strategies to control its spread or mitigate its symptoms. As a perspective solution, we investigated the efficacy of the low-temperature plasma and plasma-activated water to kill bacterial cells. Experiments were conducted in vitro to test the biocidal effect of the direct application of a Surface Dielectric Barrier Discharge (SDBD) plasma on bacteria cells and Plasma Activated Water (PAW). PAW activity was tested as a possible biocidal agent that can move freely in the xylem network paving the way to test the strategy on infected plants. The results showed a high decontamination rate even for cells of XfDD embedded in biofilms grown on solid media and complete inactivation in liquid culture medium.

Aerial and underground organs display specific metabolic strategies to cope with water stress under rising atmospheric CO2 in Fagus sylvatica L

Beech is known to be a moderately drought-sensitive tree species, and future increases in atmospheric concentrations of CO₂ ([CO₂ ]) could influence its ecological interactions, also with changes at the metabolic level. The metabolome of leaves and roots of drought-stressed beech seedlings grown under two different [CO₂ ] (400 (aCO₂ ) and 800 (eCO₂ ) ppm) was analyzed together with gas exchange parameters and water status. Water stress estimated from predawn leaf water potential (Ψ_pd ) was similar under both [CO₂ ], although eCO₂ had a positive impact on net photosynthesis and intrinsic water use efficiency. The aerial and underground organs showed different metabolomes. Leaves mainly stored C metabolites, while those of N and P accumulated differentially in roots. Drought triggered the proline and N-rich amino acids biosynthesis in roots through the activation of arginine and proline pathways. Besides the TCA cycle, polyols and soluble sugar biosynthesis were activated in roots, with no clear pattern seen in the leaves, prioritizing the root functioning as metabolites sink. eCO₂ slightly altered this metabolic acclimation to drought, reflecting mitigation of its effect. The leaves showed only minor changes, investing C surplus in secondary metabolites and malic acid. The TCA cycle metabolites and osmotically active substances increased in roots, but many other metabolites decreased as if the water stress was dampened. Above- and belowground plant metabolomes were differentially affected by two drivers of climate change, water scarcity and high [CO₂ ], showing different chemical responsiveness that could modulate the tree adaptation to future climatic scenarios.

Seasonal Variation in Selected Biochemical Traits in the Leaves of Co-Occurring Invasive and Native Plant Species under Mediterranean Conditions

The success of invasive alien species (IAS) is often linked to differences in functional traits in relation to other, either native or non-invasive, species. Two of the most problematic IAS in the Mediterranean area belong to Hakea and Acacia genera that often invade pine plantations. Therefore, the aim of this study was to assess the seasonal variations in photosynthetic pigments, total phenolics, and non-structural carbohydrates (NSC), including total soluble sugars (SS) and starch (St), and lipid peroxidation, in terms of malondialdehyde (MDA) in the leaves of evergreen species, two IAS (Hakea sericea and Acacia melanoxylon) and one native (Pinus pinaster), throughout 2019. All parameters showed a pronounced seasonal variability while also differing across species. Generally, the lowest contents of photosynthetic pigments, phenolics and SS were noted in early spring, along with the highest St and NSC values. On the other hand, higher photosynthetic pigment and lower NSC contents were measured in early autumn and early winter. When these parameters were compared across the three species, the IAS had significantly higher content of photosynthetic pigments, mainly chlorophyll b and total chlorophyll, and lower total phenolics and MDA concentrations in their leaves than Pinus pinaster. Differences in seasonal patterns were also observed. Hakea sericea and Acacia melanoxylon had considerably higher chlorophyll, SS and NSC contents in the early autumn, while Pinus pinaster had higher St and MDA contents in early summer. Overall, the biochemical characteristics of leaves of the studied IAS can explain their success in the Mediterranean area, in terms of tolerance to stressful environmental conditions.

Effects of Exogenous Phthalic Acid on Seed Germination, Root Physiological Characteristics, and Mineral Element Absorption of Watermelon

To understand the effect of exogenous PA on the watermelon root system, the watermelon variety ‘Zaojia 84–24’ was used as experimental material. This study investigated the effects of allelochemicals DIBP and DOP at varying different concentrations (0, 0.05, 0.1, 0.5, 1, and 4 mmol·L−1) on the physiological characteristics and mineral content of watermelon roots. The results revealed that proper PA treatment concentrations (0.05~0.1 mmol·L−1) promoted seed germination, increased the number of RBCs and the survival rate of RBCs, and enhanced the activities of PME and dehydrogenase in watermelon roots. In addition, proper PA treatment concentrations (0.05~0.1 mmol·L−1) promoted the activities of SOD, POD, CAT, and NR in watermelon roots. The contents of MDA and soluble protein were increased at 0.05~4 mmol·L−1 PA. In addition, proper PA treatment concentrations promoted the absorption and accumulation of P, K, Ca, Fe, Cu, and Zn elements in watermelon roots. These results indicate that PA at a concentration of 0.05~0.5 mmol·L−1 can promote watermelon seed germination, improve antioxidant enzyme activity of watermelon roots, and maintain normal physiological activities of watermelon by affecting absorption and accumulation of mineral elements in the root system.

Induced systemic tolerance mediated by plant-microbe interaction in maize (Zea mays L.) plants under hydrocarbon contamination

The present investigation was committed to examining the effect of soil spiked with diesel contamination (0, 1.5, 2.5, 3.5 g diesel kg^-1 soil) on maize (Zea mays L) varieties (MMRI yellow and Pearl white) with or without bacterial consortium (Pseudomonas aeruginosa BRRI54, Acinetobacter sp. strain BRSI56, Acinetobacter sp. strain ACRH80). Seed and soil bacterial inoculation were done. The studied morphological attributes were fresh and dry weight of shoot and root of both maize varieties. The results documented that bacterial consortium caused 21%, 0.06% and 29%, 34% higher shoot and root fresh/dry weights in "Pearl white" and 14%, 15% and 32%, 22% shoot and root fresh/dry weights respectively in MMRI yellow under control conditions. The biochemical attributes of shoot and root were affected negatively by the 3.5 g diesel kg^-1 soil contamination. Bacterial consortium enhanced enzymatic activity (APX, CAT, POD, SOD, GR) and non-enzymatic (AsA, GSH, Pro, α-Toco) antioxidant and reduction in oxidative stress (H₂O₂, MDA) under hydrocarbon stress as compared to non-inoculated ones in both root and shoot organs. Among both varieties, the highest hydrocarbon removal (75, 64, and 69%) was demonstrated by MMRI yellow with bacterial consortium as compare to Pearl white showed 73, 57, 65% hydrocarbon degradation at 1.5 2.5, 3.5 g diesel kg^-1 soil contamination. Consequently, the microbe mediated biotransformation of hydrocarbons suggested that the use of PGPB would be the most beneficial selection in diesel fuel contaminated soil to overcome the abiotic stress in plants and successfully remediation of hydrocarbon in contaminated soil.

The oxidative stress and metabolic response of Acinetobacter baumannii for aPDT multiple photosensitization

The use of antimicrobial photodynamic inactivation as a non-antibiotic alternative method to inactivate Acinetobacter baumannii was described in response to the ever-growing problem of antibiotic resistance. It was found that irradiation of the bacterial suspension for 10 min reduced the number of viable cells by approximately 99% and this energy fluence was considered to be sub-lethal phototherapy. The lethal dose of laser light (cell mortality about 99.9%) was 9.54 J cm⁻², which corresponds to 30 min of irradiation. After a 15-fold phototherapy cycle, the tolerance to aPDT decreased, resulting in a decrease in the number of viable cells by 2.15 and 3.23 log₁₀ CFU/ml units with the use of sub-lethal and lethal light doses, respectively. Multiple photosensitizations decreased the biofilm formation efficiency by 25 ± 1% and 35 ± 1%, respectively. No changes in antibiotic resistance were observed, whereas the cells were more sensitive to hydrogen peroxide. Metabolomic changes after multiple photosensitization were studied and ¹H NMR measurements were used in statistical and multivariate data analysis. Many significant changes in the levels of the metabolites were detected demonstrating the response of A. baumannii to oxidative stress.

Condensed tannins as antioxidants that protect poplar against oxidative stress from drought and UV-B

Condensed tannins (CTs, proanthocyanidins) are widespread polymeric flavan-3-ols known for their ability to bind proteins. In poplar (Populus spp.), leaf condensed tannins are induced by both biotic and abiotic stresses, suggesting diverse biological functions. Here we demonstrate the ability of CTs to function as physiological antioxidants, preventing oxidative and cellular damage in response to drought and UV-B irradiation. Chlorophyll fluorescence was used to monitor photosystem II performance, and both hydrogen peroxide and malondialdehyde content was assayed as a measure of oxidative damage. Transgenic MYB-overexpressing poplar (Populus tremula × P. tremuloides) with high CT content showed reduced photosystem damage and lower hydrogen peroxide and malondialdehyde content after drought and UV-B stress. This antioxidant effect of CT was observed using two different poplar MYB CT regulators, in multiple independent lines and different genetic backgrounds. Additionally, low-CT MYB134-RNAi transgenic poplars showed enhanced susceptibility to drought-induced oxidative stress. UV-B radiation had different impacts than drought on chlorophyll fluorescence, but all high-CT poplar lines displayed reduced sensitivity to both stresses. Our data indicate that CTs are significant defences against oxidative stress. The broad distribution of CTs in forest systems that are exposed to diverse abiotic stresses suggests that these compounds have wider functional roles than previously realized.

An integrated physiology, cytology, and proteomics analysis reveals a network of sugarcane protoplast responses to enzymolysis

The protoplast experimental system eis an effective tool for functional genomics and cell fusion breeding. However, the physiological and molecular mechanisms of protoplast response to enzymolysis are not clear, which has become a major obstacle to protoplast regeneration. Here, we used physiological, cytological, proteomics and gene expression analysis to compare the young leaves of sugarcane and enzymolized protoplasts. After enzymatic digestion, we obtained protoplasts with viability of > 90%. Meanwhile, the content of malondialdehyde, an oxidation product, increased in the protoplasts following enzymolysis, and the activity of antioxidant enzymes, such as peroxidase (POD), catalase (CAT), acid peroxidase (APX), and O^2-, significantly decreased. Cytologic analysis results showed that, post enzymolysis, the cell membranes were perforated to different degrees, the nuclear activity was weakened, the nucleolus structure was not obvious, and the microtubules depolymerized and formed several short rod-like structures in protoplasts. In this study, a proteomics approaches was used to identify proteins of protoplasts in response to the enzymatic digestion process. GO, KEGG, and KOG enrichment analyses revealed that the abundant proteins were mainly involved in bioenergetic metabolism, cellular processes, osmotic stress, and redox homeostasis of protoplasts, which allow for protein biosynthesis or degradation. RT-qPCR analysis revealed that the expression of osmotic stress resistance genes, such as DREB, WRKY, MAPK4, and NAC, was upregulated, while that of key regeneration genes, such as CyclinD3, CyclinA, CyclinB, Cdc2, PSK, CESA, and GAUT, was significantly downregulated in the protoplasts. Hierarchical clustering and identification of redox proteins and oxidation products showed that these proteins were involved in dynamic networks in response to oxidative stress after enzymolysis. Our findings can facilitate the development of a standard system to produce regenerated protoplasts using molecular markers and antibody detection of enzymolysis.

Salicylic acid: A key regulator of redox signalling and plant immunity

In plants, the reactive oxygen species (ROS) formed during normal conditions are essential in regulating several processes, like stomatal physiology, pathogen immunity and developmental signaling. However, biotic and abiotic stresses can cause ROS over-accumulation leading to oxidative stress. Therefore, a suitable equilibrium is vital for redox homeostasis in plants, and there have been major advances in this research arena. Salicylic acid (SA) is known as a chief regulator of ROS; however, the underlying mechanisms remain largely unexplored. SA plays an important role in establishing the hypersensitive response (HR) and systemic acquired resistance (SAR). This is underpinned by a robust and complex network of SA with Non-Expressor of Pathogenesis Related protein-1 (NPR1), ROS, calcium ions (Ca²⁺), nitric oxide (NO) and mitogen-activated protein kinase (MAPK) cascades. In this review, we summarize the recent advances in the regulation of ROS and antioxidant defense system signalling by SA at the physiological and molecular levels. Understanding the molecular mechanisms of how SA controls redox homeostasis would provide a fundamental framework to develop approaches that will improve plant growth and fitness, in order to meet the increasing global demand for food and bioenergy.

Biochemical and Metabolic Plant Responses toward Polycyclic Aromatic Hydrocarbons and Heavy Metals Present in Atmospheric Pollution

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) are toxic components of atmospheric particles. These pollutants induce a wide variety of responses in plants, leading to tolerance or toxicity. Their effects on plants depend on many different environmental conditions, not only the type and concentration of contaminant, temperature or soil pH, but also on the physiological or genetic status of the plant. The main detoxification process in plants is the accumulation of the contaminant in vacuoles or cell walls. PAHs are normally transformed by enzymatic plant machinery prior to conjugation and immobilization; heavy metals are frequently chelated by some molecules, with glutathione, phytochelatins and metallothioneins being the main players in heavy metal detoxification. Besides these detoxification mechanisms, the presence of contaminants leads to the production of the reactive oxygen species (ROS) and the dynamic of ROS production and detoxification renders different outcomes in different scenarios, from cellular death to the induction of stress resistances. ROS responses have been extensively studied; the complexity of the ROS response and the subsequent cascade of effects on phytohormones and metabolic changes, which depend on local concentrations in different organelles and on the lifetime of each ROS species, allow the plant to modulate its responses to different environmental clues. Basic knowledge of plant responses toward pollutants is key to improving phytoremediation technologies.

Metabolomic analyses on microbial primary and secondary oxidative stress responses

Food safety is veryimportant in our daily life. In food processing or disinfection, microorganisms are commonly exposed to oxidative stress perturbations. However, microorganisms can adapt and respond to physicochemical interventions, leading to difficulty and complexity for food safety assurance. Therefore, understanding the response mechanisms of microbes and providing an overview of the responses under oxidative stress conditions are beneficial for ensuring food safety for the industry. The current review takes the metabolomics approach to reveal small metabolite signatures and key pathway alterations during oxidative stress at the molecular and technical levels. These alterations are involved in primary oxidative stress responses due to inactivation treatments such as using hypochlorite (HOCl), hydrogen peroxide (H₂ O₂ ), electrolyzed water (EW), irradiation, pulsed light (PL), electron beam (EB), and secondary oxidative stress responses due to exposures to excessive conditions such as heat, pressure, acid, and alkaline. Details on the putative origin of exogenous or endogenous reactive oxygen species (ROS) are discussed, with particular attention paid to their effects on lipid, amino acid, nucleotide, and carbohydrate metabolism. In addition, mechanisms on counteracting oxidative stresses, stabilization of cell osmolality as well as energy provision for microbes to survive are also discussed.

Exogenous Application of Methyl Jasmonate and Salicylic Acid Mitigates Drought-Induced Oxidative Damages in French Bean (Phaseolus vulgaris L.)

Drought stress impairs the normal growth and development of plants through various mechanisms including the induction of cellular oxidative stresses. The aim of this study was to evaluate the effect of the exogenous application of methyl jasmonate (MeJA) and salicylic acid (SA) on the growth, physiology, and antioxidant defense system of drought-stressed French bean plants. Application of MeJA (20 μM) or SA (2 mM) alone caused modest reductions in the harmful effects of drought. However, combined application substantially enhanced drought tolerance by improving the physiological activities and antioxidant defense system. The drought-induced generation of O₂^●− and H₂O₂, the MDA content, and the LOX activity were significantly lower in leaves when seeds or leaves were pre-treated with a combination of MeJA (10 μM) and SA (1 mM) than with either hormone alone. The combined application of MeJA and SA to drought-stressed plants also significantly increased the activities of the major antioxidant enzymes superoxide dismutase, catalase, peroxidase, glutathione peroxidase, and glutathione-S-transferase as well as the enzymes of the ascorbate–glutathione cycle. Taken together, our results suggest that seed or foliar application of a combination of MeJA and SA restore growth and normal physiological processes by triggering the antioxidant defense system in drought-stressed plants.

Metabolic responses of date palm (Phoenix dactylifera L.) leaves to drought differ in summer and winter climate

Drought negatively impacts growth and productivity of plants, particularly in arid and semi-arid regions. Although drought events can take place in summer and winter, differences in the impact of drought on physiological processes between seasons are largely unknown. The aim of this study was to elucidate metabolic strategies of date palms in response to drought in summer and winter season. To identify such differences, we exposed date palm seedlings to a drought-recovery regime, both in simulated summer and winter climate. Leaf hydration, carbon discrimination (${\Delta}$13C), and primary and secondary metabolite composition and contents were analyzed. Depending on season, drought differently affected physiological and biochemical traits of the leaves. In summer, drought induced significantly decreased leaf hydration, concentrations of ascorbate, most sugars, primary and secondary organic acids, as well as phenolic compounds, while thiol, amino acid, raffinose and individual fatty acid contents were increased compared with well-watered plants. In winter, drought had no effect on leaf hydration, ascorbate and fatty acids contents, but resulted in increased foliar thiol and amino acid levels as observed in summer. Compared with winter, foliar traits of plants exposed to drought in summer only partly recovered after re-watering. Memory effects on water relations, and primary and secondary metabolites seem to prepare foliar traits of date palms for repeated drought events in summer. Apparently, a well-orchestrated metabolic network, including the anti-oxidative system, compatible solutes accumulation and osmotic adjustment, and maintenance of cell-membrane stability strongly reduces the susceptibility of date palms to drought. These mechanisms of drought compensation may be more frequently required in summer.

Stress response of lettuce (Lactuca sativa) to environmental contamination with selected pharmaceuticals: A proteomic study

Pharmaceutical compounds have been found in rivers and treated wastewaters. They often contaminate irrigation waters and consequently accumulate in edible vegetables, causing changes in plants metabolism. The main objective of this work is to understand how lettuce plants cope with the contamination from three selected pharmaceuticals using a label free proteomic analysis. A lettuce hydroponic culture, grown for 36 days, was exposed to metformin, acetaminophen and carbamazepine (at 1 mg/L), during 8 days, after which roots and leaves were sampled and analysed using a liquid chromatography-mass spectrometry proteomics-based approach. In roots, a total of 612 proteins showed differentially accumulation while in leaves 237 proteins were identified with significant differences over controls. Carbamazepine was the contaminant that most affected protein abundance in roots, while in leaves the highest number of differentially accumulated proteins was observed for acetaminophen. In roots under carbamazepine, stress related protein species such as catalase, superoxide dismutase and peroxidases presented higher abundance. Ascorbate peroxidase increased in roots under metformin. Cell respiration protein species were affected by the presence of the three pharmaceuticals suggesting possible dysregulation of the Krebs cycle. Acetaminophen caused the main differences in respiration pathways, with more emphasis in leaves. Lettuce plants revealed different tolerance levels when contaminants were compared, being more tolerant to metformin presence and less tolerant to carbamazepine. SIGNIFICANCE: The significant increase of emerging contaminants in ecosystems makes essential to understand how these compounds may affect the metabolism of different organisms. Our study contributes with a detailed approach of the main interactions that may occur in plant metabolism when subjected to the stress induced by three different pharmaceuticals (acetaminophen, carbamazepine and metformin).

Cooperation of chloroplast ascorbate peroxidases and proton gradient regulation 5 is critical for protecting Arabidopsis plants from photo-oxidative stress

High-light (HL) stress enhances the production of H₂ O₂ from the photosynthetic electron transport chain in chloroplasts, potentially causing photo-oxidative damage. Although stromal and thylakoid membrane-bound ascorbate peroxidases (sAPX and tAPX, respectively) are major H₂ O₂ -scavenging enzymes in chloroplasts, their knockout mutants do not exhibit a visible phenotype under HL stress. Trans-thylakoid proton gradient (∆pH)-dependent mechanisms exist for controlling H₂ O₂ production from photosynthesis, such as thermal dissipation of light energy and downregulation of electron transfer between photosystems II and I, and these may compensate for the lack of APXs. To test this hypothesis, we focused on a proton gradient regulation 5 (pgr5) mutant, wherein both ∆pH-dependent mechanisms are impaired, and an Arabidopsis sapx tapx double mutant was crossed with the pgr5 single mutant. The sapx tapx pgr5 triple mutant exhibited extreme sensitivity to HL compared with its parental lines. This phenotype was consistent with cellular redox perturbations and enhanced expression of many oxidative stress-responsive genes. These findings demonstrate that the PGR5-dependent mechanisms compensate for chloroplast APXs, and vice versa. An intriguing finding was that the failure of induction of non-photochemical quenching in pgr5 (because of the limitation in ∆pH formation) was partially recovered in sapx tapx pgr5. Further genetic studies suggested that this recovery was dependent on the NADH dehydrogenase-like complex-dependent pathway for cyclic electron flow around photosystem I. Together with data from the sapx tapx npq4 mutant, we discuss the interrelationship between APXs and ∆pH-dependent mechanisms under HL stress.

The Arabidopsis mediator complex subunit 8 regulates oxidative stress responses

Signaling events triggered by hydrogen peroxide (H2O2) regulate plant growth and defense by orchestrating a genome-wide transcriptional reprogramming. However, the specific mechanisms that govern H2O2-dependent gene expression are still poorly understood. Here, we identify the Arabidopsis Mediator complex subunit MED8 as a regulator of H2O2 responses. The introduction of the med8 mutation in a constitutive oxidative stress genetic background (catalase-deficient, cat2) was associated with enhanced activation of the salicylic acid pathway and accelerated cell death. Interestingly, med8 seedlings were more tolerant to oxidative stress generated by the herbicide methyl viologen (MV) and exhibited transcriptional hyperactivation of defense signaling, in particular salicylic acid- and jasmonic acid-related pathways. The med8-triggered tolerance to MV was manipulated by the introduction of secondary mutations in salicylic acid and jasmonic acid pathways. In addition, analysis of the Mediator interactome revealed interactions with components involved in mRNA processing and microRNA biogenesis, hence expanding the role of Mediator beyond transcription. Notably, MED8 interacted with the transcriptional regulator NEGATIVE ON TATA-LESS, NOT2, to control the expression of H2O2-inducible genes and stress responses. Our work establishes MED8 as a component regulating oxidative stress responses and demonstrates that it acts as a negative regulator of H2O2-driven activation of defense gene expression.

Acetaminophen Induces an Antioxidative Response in Lettuce Plants

Contaminants of environmental concern, like pharmaceuticals, are being detected in increasing amounts in soils and irrigation waters and can thus be taken up by plants. In this work, the uptake of acetaminophen (ACT) by lettuce plants was evaluated through a hydroponic experiment at different concentrations (0, 0.1, 1 and 5 mg L⁻¹ ACT). The pathways related to oxidative stress induced by ACT were studied in lettuce leaves and roots at 1, 8 and 15 days after exposure. Stress indicators such as hydrogen peroxide and malondialdehyde (MDA) contents were analyzed, revealing increases in plants contaminated with ACT in comparison to control, confirming the occurrence of oxidative stress, with the exception of MDA in leaves. The enzymatic activities of catalase, superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and glutathione peroxidase, directly involved in the antioxidative system, showed significant differences when compared to control plants, and, depending on the enzyme and the tissue, different trends were observed. Glutathione reductase revealed a decrease in contaminated leaves, which may imply a specific impact of ACT in the glutathione cycle. Significant increases were found in the anthocyanin content of leaves, both with exposure time and ACT concentration, indicating an antioxidative response induced by ACT contamination.

Strategies in a metallophyte species to cope with manganese excess

The effect of exposure to high Mn concentration was studied in a metallophyte species, Erica andevalensis, using hydroponic cultures with a range of Mn concentrations (0.06, 100, 300, 500, and 700 mg L^-1). At harvest, biomass production, element uptake, and biochemical indicators of metal stress (leaf pigments, organic acids, amino acids, phenols, and activities of catalase, peroxidase, superoxide dismutase) were determined in leaves and roots. Increasing Mn concentrations led to a decrease in biomass accumulation, and tip leaves chlorosis was the only toxicity symptom detected. In a similar way, photosynthetic pigments (chlorophylls a and b, and carotenoids) were affected by high Mn levels. Among organic acids, malate and oxalate contents in roots showed a significant increase at the highest Mn concentration, while in leaves, Mn led to an increasing trend in citrate and malate contents. An increase of Mn also induced an increase in superoxide dismutase activity in roots and catalase activity in leaves. As well, significant changes in free amino acids were induced by Mn concentrations higher than 300 mg L^-1, especially in roots. No significant changes in phenolic compounds were observed in the leaves, but root phenolics were significantly increased by increasing Mn concentrations in treatments. When Fe supply was increased 10 and 20 times (7-14 mg Fe L^-1 as Fe-EDDHA) in the nutrient solutions at the highest Mn concentration (700 mg Mn L^-1), it led to significant increases in photosynthetic pigments and biomass accumulation. Manganese was mostly accumulated in the roots, and the species was essentially a Mn excluder. However, considering the high leaf Mn concentration recorded without toxicity symptoms, E. andevalensis might be rated as a Mn-tolerant species.

Oxidative Stress-Induced Alteration of Plant Central Metabolism

Oxidative stress is an integral component of various stress conditions in plants, and this fact largely determines the substantial overlap in physiological and molecular responses to biotic and abiotic environmental challenges. In this review, we discuss the alterations in central metabolism occurring in plants experiencing oxidative stress. To focus on the changes in metabolite profile associated with oxidative stress per se, we primarily analyzed the information generated in the studies based on the exogenous application of agents, inducing oxidative stress, and the analysis of mutants displaying altered oxidative stress response. Despite of the significant variation in oxidative stress responses among different plant species and tissues, the dynamic and transient character of stress-induced changes in metabolites, and the strong dependence of metabolic responses on the intensity of stress, specific characteristic changes in sugars, sugar derivatives, tricarboxylic acid cycle metabolites, and amino acids, associated with adaptation to oxidative stress have been detected. The presented analysis of the available data demonstrates the oxidative stress-induced redistribution of metabolic fluxes targeted at the enhancement of plant stress tolerance through the prevention of ROS accumulation, maintenance of the biosynthesis of indispensable metabolites, and production of protective compounds. This analysis provides a theoretical basis for the selection/generation of plants with improved tolerance to oxidative stress and the development of metabolic markers applicable in research and routine agricultural practice.

Modulations of the antioxidants defence system in two maize hybrids during flooding stress

Flooding stress nowadays is one of the major stressors for plants under climate change. This kind of stress may cause severe depression of the plant's growth through inhibition of photosynthesis and oxidative cell damage as well as changes in cell respiration. The present work aimed to study the effect of flooding stress on oxidative and antioxidative parameters in leaves of two maize hybrids (ZP 555 and ZP 606). Leaves of maize plants at the stage of three fully developed leaves were harvested after 6, 24, 72, and 144 h of applied flooding stress. Leaves were used for determination of physiological (the content of photosynthetic pigments and soluble proteins), oxidative stress parameters (the content of malondialdehyde (MDA) and H₂O₂) as well as antioxidants (the total polyphenols content, and activity of antioxidative enzymes [catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1), and Class III peroxidases (POX, EC, 1.11.1.7)]). Results indicated that flooding stress-induced time-dependent changes of measured parameters and those hybrids differ in response to stress. The noticeable difference between hybrids was detected in the H₂O₂ and MDA content. An increase in the activity of SOD, POX and polyphenols content, with the most pronounced changes in POX activity and polyphenols concentration, could minimize the cellular damage caused by flooding. The results of the present study suggest that a more robust antioxidative metabolism is essential under flooding stress and could be a protective strategy against oxidative damage induced by flooding in ZP 606 maize plants compared to ZP 555 plants.

Comparison of Light Condition-Dependent Differences in the Accumulation and Subcellular Localization of Glutathione in Arabidopsis and Wheat

This study aimed to clarify whether the light condition-dependent changes in the redox state and subcellular distribution of glutathione were similar in the dicotyledonous model plant Arabidopsis (wild-type, ascorbate- and glutathione-deficient mutants) and the monocotyledonous crop species wheat (Chinese Spring variety). With increasing light intensity, the amount of its reduced (GSH) and oxidized (GSSG) form and the GSSG/GSH ratio increased in the leaf extracts of both species including all genotypes, while far-red light increased these parameters only in wheat except for GSH in the GSH-deficient Arabidopsis mutant. Based on the expression changes of the glutathione metabolism-related genes, light intensity influences the size and redox state of the glutathione pool at the transcriptional level in wheat but not in Arabidopsis. In line with the results in leaf extracts, a similar inducing effect of both light intensity and far-red light was found on the total glutathione content at the subcellular level in wheat. In contrast to the leaf extracts, the inducing influence of light intensity on glutathione level was only found in the cell compartments of the GSH-deficient Arabidopsis mutant, and far-red light increased it in both mutants. The observed general and genotype-specific, light-dependent changes in the accumulation and subcellular distribution of glutathione participate in adjusting the redox-dependent metabolism to the actual environmental conditions.

Liquiritoside Alleviated Pb Induced Stress in Brassica rapa subsp. Parachinensis: Modulations in Glucosinolate Content and Some Physiochemical Attributes

Current research was conducted to explore the effects of liquiritoside on the growth and physiochemical features of Chinese flowering cabbage (Brassica rapa subsp. parachinensis) under lead (Pb) stress. Lead stressed B. rapa plants exhibited decreased growth parameters, chlorophyll, and carotenoid contents. Moreover, Pb toxicity escalated the synthesis of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), flavonoids, phenolics, and proline in treated plants. Nevertheless, foliar application of liquiritoside mitigated Pb toxicity by decreasing oxidative stress by reducing cysteine, H₂O_2, and MDA contents in applied plants. Liquiritoside significantly increased plant height, shoot fresh weight and dry weight, number of leaves, and marketable value of Chinese flowering cabbage plants exposed to Pb toxicity. This biotic elicitor also enhanced the proline, glutathione, total phenolics, and flavonoid contents in Chinese flowering cabbage plants exposed to Pb stress compared with the control. Additionally, total glucosinolate content, phytochelatins (PCs), and non-protein thiols were effectively increased in plants grown under Pb regimes compared with the control plants. Overall, foliar application of liquiritoside can markedly alleviate Pb stress by restricting Pb translocation in Chinese flowering cabbage.

Phenolics from the Bolivian highlands food plant Ombrophytum subterraneum (Aspl.) B. Hansen (Balanophoraceae): Antioxidant and α-glucosidase inhibitory activity

The Balanophoraceae Ombrophytum subterraneum is an endemic highland food plant occurring in Bolivia, northern Argentina and Chile. The upper part of this parasitic plant is eaten fresh. The aim of this work was to characterize the compounds occurring in the edible part and to assess any differences between the inflorescence and tuber. Ethanol extracts of the different plant parts were analyzed for antioxidant activity by the ORAC, TEAC, FRAP, CUPRAC and DPPH methods as well as for the effect on enzymes related to metabolic syndrome (α-amylase, α-glucosidase and pancreatic lipase). The main constituents were isolated by a combination of gel permeation in Sephadex LH-20 and countercurrent chromatography (CCC). Five compounds were isolated and fully identified by spectroscopic and spectrometric means. The new 3',5,5',7-tetrahydroxyflavanone 7-O-β-D-1 → 6 diglucoside was isolated for the first time. HPLC-ESI-MS/MS analysis allowed the identification of 19 compounds, including flavanones, flavanols, flavonols, dehydroflavonols and lignans, mainly as glycosides. A strong inhibition towards α-glucosidase was observed for the edible parts (IC₅₀: 1.46 µg/mL) as well as for the tuber and inflorescence (IC₅₀: 1.56 µg/mL and 0.87 µg/mL, respectively). A significant correlation was established between the total phenolic and the antioxidant capacity of the extracts as well as with the content of the new flavanone diglucoside. This is the first comprehensive report on the naturally occurring antioxidants and enzyme inhibitors from this native highland food resource.