Ascorbate and glutathione: the heart of the redox hub

Simultaneous quantification of peroxidase/ascorbate in vegetables with slope and intercept of kinetic curves in a flow-injection recirculating-catalysis system

In using a flow-injection recirculating-catalysis system developed by us to research the simultaneous quantification for peroxidase and ascorbate, it was discovered that the concentrations of peroxidase activity and ascorbate are correlative with the slope and the negative intercept of the linear response curve during a peroxidase-catalyzed kinetic course. Therefore, based on this finding, a new analytical method and a simplified equation for quantifying the peroxidase activity concentration were proposed, Then, test conditions were optimized, finally the use of the method has realized the simultaneous determination for peroxidase of 2-40 U/L and ascorbate of 0.4-12 mg/L in various vegetables (60 μL). The assayed results were consistent with the comparison method, in which the repeatability (RSD < 1.43%, n = 11) was satisfactory. Another important conclusion obtained in this study is that the determination of the peroxidase activity in biosamples must use the kinetic curve method for fear of the influence from the ascorbate's lag phase.

Impact of Biochar Application at Water Shortage on Biochemical and Physiological Processes in Medicago ciliaris

The application of biochar is mostly used to improve soil fertility, water retention capacity and nutrient uptake. The present study was conducted in order to study the impact of biochar at water deficiency conditions on the physiological and biochemical processes of Medicago ciliaris seedlings. Seedlings were cultivated under greenhouse conditions in pots filled with a mixture of soil and sand mixed in the presence or absence of 2% biochar. Plants of uniform size were subjected after a pretreatment phase (72 days) either to low (36% water holding capacity, water potential low) or high soil water potential (60% water holding capacity, water potential high). Pots were weighed every day to control and maintain a stable water holding capacity. In Medicago ciliaris, drought led to a significant reduction in plant growth and an increase in the root/shoot ratio. The growth response was accompanied by a decreased stomatal conductance and a reduction of the net CO₂ assimilation rate and water use efficiency. The associated higher risk of ROS production was indicated by a high level of lipid peroxidation, high antioxidant activities and high proline accumulation. Soil amendment with biochar enhanced the growth significantly and supported the photosynthetic apparatus of Medicago ciliaris species by boosting chlorophyll content and A_net both under well and insufficient watered plants and water use efficiency in case of water shortage. This increase of water use efficiency was correlated with the biochar-mediated decrease of the MDA and proline contents in the leaves buffering the impact of drought on photosynthetic apparatus by increasing the activity of enzymatic antioxidants SOD, APX, GPOX and GR and non-enzymatic antioxidants, such as AsA and DHAsA, giving the overall picture of a moderate stress response. These results confirmed the hypothesis that biochar application significantly reduces both the degree of stress and the negative impact of oxidative stress on Medicago ciliaris plants. These results implied that this species could be suitable as a cash pasture plant in the development of agriculture on dry wasteland in a future world of water shortages.

Physiological and Antioxidant Response to Different Water Deficit Regimes of Flag Leaves and Ears of Wheat Grown under Combined Elevated CO2 and High Temperature

Triticum aestivum L. cv. Gazul is a spring wheat widely cultivated in Castilla y León (Spain). Potted plants were grown in a scenario emulating the climate change environmental conditions expected by the end of this century, i.e., with elevated CO₂ and high temperature under two water deficit regimes: long (LWD) and terminal (TWD). Changes in biomass and morphology, the content of proline (Pro), ascorbate (AsA) and glutathione (GSH), and enzymatic antioxidant activities were analyzed in flag leaves and ears. Additionally, leaf gas exchange was measured. LWD caused a decrease in biomass and AsA content but an increase in Pro content and catalase and GSH reductase activities in flag leaves, whereas TWD produced no significant changes. Photosynthesis was enhanced under both water deficit regimes. Increase in superoxide dismutase activity and Pro content was only observed in ears under TWD. The lack of a more acute effect of LWD and TWD on both organs was attributed to the ROS relieving effect of elevated CO₂. Gazul acted as a drought tolerant variety with anisohydric behavior. A multifactorial analysis showed better adaptation of ears to water deficit than flag leaves, underlining the importance of this finding for breeding programs to improve grain yield under future climate change.

Peroxisome-Mediated Reactive Oxygen Species Signals Modulate Programmed Cell Death in Plants

Peroxisomes are a class of simple organelles that play an important role in plant reactive oxygen species (ROS) metabolism. Experimental evidence reveals the involvement of ROS in programmed cell death (PCD) in plants. Plant PCD is crucial for the regulation of plant growth, development and environmental stress resistance. However, it is unclear whether the ROS originated from peroxisomes participated in cellular PCD. Enzymes involved in the peroxisomal ROS metabolic pathways are key mediators to figure out the relationship between peroxisome-derived ROS and PCD. Here, we summarize the peroxisomal ROS generation and scavenging pathways and explain how peroxisome-derived ROS participate in PCD based on recent progress in the functional study of enzymes related to peroxisomal ROS generation or scavenging. We aimed to elucidate the role of the peroxisomal ROS regulatory system in cellular PCD to show its potential in terms of accurate PCD regulation, which contribute to environmental stress resistance.

Harder, better, faster, stronger: Frost tolerance of Eucalyptus benthamii under cold acclimation

Eucalypts are the most planted hardwood trees worldwide because of their very rapid growth, exceptional wood quality and adaptability. However, most commercial species and derived hybrids are sensitive to frost, which remains as the largest obstacle to their introduction in warm/temperate climates. As evergreen species, Eucalypts have developed the ability to tolerate frost events based on physiological and molecular responses triggered by previous exposure to cold temperatures, globally named cold acclimation. To characterize the acclimation process in two species with different tolerance to frost, E. grandis (Eg) and E. benthamii (Eb), seedlings were exposed for different times to low temperatures. Frost tolerance was estimated in leaves by an electrolyte leakage assay, and metabolome and morpho-physiological changes studied and correlated to the observed acclimation responses. Eb showed higher basal frost tolerance and an earlier and stronger acclimation response to cold temperatures than in the frost sensitive Eg. Eb was able to modify several morpho-physiological parameters, with a restriction in plant height, leaf area and leaf fresh weight during acclimation. Metabolome characterization allowed us to differentiate species and strengthen our understanding of their acclimation response dynamics. Interestingly, Eb displayed an early phase of sugar accumulation followed by a rise of different metabolites with possible roles as osmolytes and antioxidants, that correlated to frost tolerance and may explain Eb higher capacity to acclimate. This novel approach has helped us to point to the main metabolic processes underlying the cold tolerance acquisition process in two relevant Eucalyptus species.

Co-over expression of Ascorbate Glutathione pathway enzymes improve mercury tolerance in tomato

The genetic modification of plants for the removal of inorganic pollutants from contaminated soil and water bodies is an emerging area for addressing environmental concerns. This approach is based on the ability of plants to take up and accumulate heavy metals, with efficiency being dependent on the underlying mechanisms of heavy metal accumulation and tolerance. A robust antioxidant pathway is determinantal for heavy metal uptake and accumulation and, therefore, in this study, we evaluated the transgenic tomato plants installed with Ascorbate Glutathione (ASA-GSH) pathway genes for uptake, accumulation, and response to mercury (Hg). We observed that ASA-GSH overexpressing lines were resilient to Hg stress as they displayed higher photosynthetic activity and increased photosynthetic gas exchange parameters with a concomitant decrease in ion leakage under Hg stress. Additionally, transgenic lines accumulated high osmolytes and showed enhanced activity of antioxidant enzymes. Moreover, the results of SEM and confocal microscopy confirmed least damage to plant tissue in ASA-GSH overexpressing lines compared to wild-type under Hg-stress which was further supported by Atomic absorption study that revealed a significant decline in Hg accumulation in the leaves of transgenic lines compared to wild-type under stress conditions. In conclusion, pyramiding of ASA-GSH pathway genes in tomato plants is an efficient approach for the development of Hg-resistant tomato plants and the reclamation of Hg-contaminated sites.

Application of zinc oxide nanoparticles as fertilizer boosts growth in rice plant and alleviates chromium stress by regulating genes involved in oxidative stress

Chromium toxicity impairs the productivity of rice crops and raises a major concern worldwide and thus, it calls for unconventional and sustainable means of crop production. In this study, we identified the implication of zinc oxide nanoparticles (ZnO NPs) in promoting plant growth and ameliorating chromium-induced stress in seedlings of rice (Oryza sativa). This investigation demonstrates that the exogenous supplementation of ZnO NPs at 25 μM activates defense mechanisms conferring rice seedlings significant tolerance against stress imposed by the exposure of 100 μM Cr(VI). Further, supplementation of this nanofertilizer reversed the inhibitory effects of Cr(VI) on growth and photosynthetic efficiency. The growth promotion was primarily associated with the function of ZnO NPs in inducing activity of antioxidative enzymes i.e. APX, DHAR, MDHAR and GR belonging to the ascorbate-glutathione cycle in the Cr-exposed seedlings, exceeding the levels in control. The overexpression of these antioxidative genes correlated concomitantly with the decrease of oxidants including SOR and H₂O₂ and the increase in the levels of non-enzymatic antioxidants: AsA and GSH.

Silicon and nitric oxide-mediated mechanisms of cadmium toxicity alleviation in wheat seedlings

The individual impact of silicon (Si) and nitric oxide (NO, as sodium nitroprusside) on metal toxicity in various plant species has been well documented; however, their combined action in the regulation of metal stress has never been tested yet. Therefore, this study investigates the effects of the combined application of Si and NO in the mitigation of Cd toxicity in wheat seedlings. Seedlings grown on Cd has a significantly declined growth due to an increased accumulation of Cd and oxidative stress markers (due to downregulation of antioxidant defense system particularly ascorbate-glutathione cycle) and a decreased accumulation of NO and Si. Additionally, the altered leaf and root structures resulted into a declined photosynthetic efficiency. However, the addition of Si and NO alone as well as combined significantly alleviated Cd toxicity in wheat seedlings by lowering the accumulation of Cd and oxidative stress markers and improving leaf and root structures, which are collectively responsible for a better photosynthetic rate under Cd toxicity, and hence an improved growth was noticed. Particularly, the application of Si and NO in combination lowered the oxidative stress markers via upregulating the antioxidant defense system (particularly AsA-GSH cycle) suggesting the increased efficacy of Si + NO against the Cd toxicity in wheat seedlings as compared to their alone treatments.

Photosynthetic, antioxidative, and metabolic adjustments of a crop plant to elevated levels of La and Ce exposure

Rare earth elements (REEs) have been widely applied as fertilizers in farmland of China for decades to improve the yield and quality of crops. Unfortunately, adverse effects on plants have been observed due to overdosing with REEs. Until now, the toxicology of REEs was mainly evaluated based on phenotypic responses, but knowledge gaps still exist concerning their metabolic effects. Here, the physiological responses and nontargeted metabolomics studies were combined to systematically explore the potential effects of La and Ce on a crop plant, wheat Triticum aestivum. It was observed that REEs accumulated in the shoots of wheat, with significant reduction of the shoot biomass at higher exposure doses. The disturbance of photosynthesis and induced oxidative stress were identified by analyzing indicators of the photosynthetic (chlorophyll a/b, carotenoid and rubisco) and antioxidant systems (POD, CAT, SOD, GSH and MDA). Furthermore, the global metabolic profiles of REEs treatment groups and the non-exposed control group were screened and compared, and the metabolomic disturbance of REEs was dose-dependent. A high overlap of significantly changed metabolites and matched disturbed biological pathways was found between La and Ce treatments, indicating similarity of their toxicity mechanism in wheat shoots. Generally, the perturbed metabolomic pathways were mainly related to carbohydrate, amino acid and nucleotide/side metabolism, suggesting a disturbance of carbon and nitrogen metabolism, which finally affected the growth of wheat. We thus proved the potential adverse effect of inappropriate application of REEs in crop plants and postulated metabolomics as a feasible tool to identify the underlying toxicological mechanisms.

Glutathione degradation activity of γ-glutamyl peptidase 1 manifests its dual roles in primary and secondary sulfur metabolism in Arabidopsis

Glutathione (GSH) functions as a major sulfur repository and hence occupies an important position in primary sulfur metabolism. GSH degradation results in sulfur reallocation and is believed to be carried out mainly by γ-glutamyl cyclotransferases (GGCT2;1, GGCT2;2, and GGCT2;3), which, however, do not fully explain the rapid GSH turnover. Here, we discovered that γ-glutamyl peptidase 1 (GGP1) contributes to GSH degradation through a yeast complementation assay. Recombinant proteins of GGP1, as well as GGP3, showed high degradation activity of GSH, but not of oxidized glutathione (GSSG), in vitro. Notably, the GGP1 transcripts were highly abundant in rosette leaves, in agreement with the ggp1 mutants constantly accumulating more GSH regardless of nutritional conditions. Given the lower energy requirements of the GGP- than the GGCT-mediated pathway, the GGP-mediated pathway could be a more efficient route for GSH degradation than the GGCT-mediated pathway. Therefore, we propose a model wherein cytosolic GSH is degraded chiefly by GGP1 and likely also by GGP3. Another noteworthy fact is that GGPs are known to process GSH conjugates in glucosinolate and camalexin synthesis; indeed, we confirmed that the ggp1 mutant contained higher levels of O-acetyl-l-Ser, a signaling molecule for sulfur starvation, and lower levels of glucosinolates and their degradation products. The predicted structure of GGP1 further provided a rationale for this hypothesis. In conclusion, we suggest that GGP1 and possibly GGP3 play vital roles in both primary and secondary sulfur metabolism.

Organelle-specific localization of glutathione in plants grown under different light intensities and spectra

Plant ascorbate and glutathione metabolism counteracts oxidative stress mediated, for example, by excess light. In this review, we discuss the properties of immunocytochemistry and transmission electron microscopy, redox-sensitive dyes or probes and bright-field microscopy, confocal microscopy or fluorescence microscopy for the visualization and quantification of glutathione at the cellular or subcellular level in plants and the quantification of glutathione from isolated organelles. In previous studies, we showed that subcellular ascorbate and glutathione levels in Arabidopsis are affected by high light stress. The use of light-emitting diodes (LEDs) is gaining increasing importance in growing indoor crops and ornamental plants. A combination of different LED types allows custom-made combinations of wavelengths and prevents damage related to high photon flux rates. In this review we provide an overview on how different light spectra and light intensities affect glutathione metabolism at the cellular and subcellular levels in plants. Findings obtained in our most recent study demonstrate that both light intensity and spectrum significantly affected glutathione metabolism in wheat at the transcriptional level and caused genotype-specific reactions in the investigated Arabidopsis lines.

Effects of ascorbic acid addition on the oxidative stress response of Oryza sativa L. plants to As(V) exposure

Accumulation of noxious elements in the edible part of crops and its impact on food safety is of increasing concern. Rice is one of the major staple food crops worldwide, including arsenic (As)-polluted areas, in which dietary As exposure is becoming a widespread health threat. Plant chemical priming has been shown to be an effective strategy to enhance tolerance to environmental stresses, including metal(loid) exposure. The priming effect of ascorbic acid (AsA) was assessed in rice seedlings exposed to As(V) in a hydroponics experiment. AsA treatment (co-addition to the growing media concomitantly (t₀) or 24 h in advance (t₂₄)) prevented an excessive accumulation of As in the roots (that decreased ∼ 60%) and stimulated the activities of photosynthetic and antioxidant attributes (∼1.2-fold) in the aerial part of the plants. The increase in proline levels in both shoots (∼2.1-fold) and roots (∼2.4-fold) was found to be the most sensitive stress parameter, and was able to reflect the AsA-induced reduction of As toxic effects (concentrations back to Control levels, both simultaneously added or added as a pretreatment) in the aerial part of the plants. However, the phytotoxic effects related to As exposure were not fully prevented by priming with AsA, and further research is needed to find alternative priming approaches.

Complementary Effects of Dark Septate Endophytes and Trichoderma Strains on Growth and Active Ingredient Accumulation of Astragalus mongholicus under Drought Stress

Drought is a major abiotic stress factor affecting plant growth and production, while utilizing beneficial endophytic fungi is one of the most promising strategies for enhancing plant growth and drought tolerance. In the current study, a pot experiment was conducted to investigate the beneficial effects of dark septate endophyte (DSE) (Macrophomina pseudophaseolina, Paraphoma radicina) and Trichoderma (Trichoderma afroharzianum, Trichoderma longibrachiatum) inoculum on Astragalus mongholicus grown in sterile soil under drought stress, alone, or in combination. The addition of Trichoderma enhanced the DSE colonization in roots regardless of the water condition. Under well-watered conditions, M. pseudophaseolina inoculation significantly enhanced the biomass and root length of A. mongholicus. The two DSE and Trichoderma inoculum significantly improved calycosin-7-O-β-D-glucoside content. However, M. pseudophaseolina + T. afroharzianum inoculation better promoted root growth, whereas co-inoculation had higher active ingredient contents compared with single inoculation, except for P. radicina + T. afroharzianum. Under drought stress, DSE and Trichoderma inoculum significantly improved root biomass, root length, calycosin-7-O-β-D-glucoside content, and activities of nitrate reductase and soil urease. P. radicina + T. afroharzianum and P. radicina + T. longibrachiatum better increased root length, and all combinations of DSE and Trichoderma had a greater impact on the increase in formononetin content compared with the single treatments. Additionally, Trichoderma relies on antioxidant enzymes, growth hormones, and the redox system (ascorbic acid−glutathione) to resist drought, while DSE strains have an additional osmotic regulation system in addition to the drought resistance function possessed by Trichoderma, and the effect of co-inoculation (especially M. pseudophaseolina + T. longibrachiatum and P. radicina + T. afroharzianum) on plant physiological parameters was greater than that of single inoculation. This study provides a new research direction for the effects of DSE and Trichoderma on medicinal plant cultivated in dryland.

The diversity and ecology of Symbiodiniaceae: A traits-based review

Among the most successful microeukaryotes to form mutualisms with animals are dinoflagellates in the family Symbiodiniaceae. These photosynthetic symbioses drive significant primary production and are responsible for the formation of coral reef ecosystems but are particularly sensitive when environmental conditions become extreme. Annual episodes of widespread coral bleaching (disassociation of the mutualistic partnership) and mortality are forecasted from the year 2060 under current trends of ocean warming. However, host cnidarians and dinoflagellate symbionts display exceptional genetic and functional diversity, and meaningful predictions of the future that embrace this biological complexity are difficult to make. A recent move to trait-based biology (and an understanding of how traits are shaped by the environment) has been adopted to move past this problem. The aim of this review is to: (1) provide an overview of the major cnidarian lineages that are symbiotic with Symbiodiniaceae; (2) summarise the symbiodiniacean genera associated with cnidarians with reference to recent changes in taxonomy and systematics; (3) examine the knowledge gaps in Symbiodiniaceae life history from a trait-based perspective; (4) review Symbiodiniaceae trait variation along three abiotic gradients (light, nutrients, and temperature); and (5) provide recommendations for future research of Symbiodiniaceae traits. We anticipate that a detailed understanding of traits will further reveal basic knowledge of the evolution and functional diversity of these mutualisms, as well as enhance future efforts to model stability and change in ecosystems dependent on cnidarian-dinoflagellate organisms.

Attenuation of Chilling Injury and Improving Antioxidant Capacity of Persimmon Fruit by Arginine Application

Persimmon is a climacteric perishable fruit with a short storage life. In recent years, using natural compounds that are safe for human health and environment have obtained more attention in postharvest investigations. The current research was conducted to study efficacy of postharvest L-arginine treatment at 0, 0.3, and 0.6 mM in improving chilling tolerance and maintaining the nutritional quality of persimmon fruit during low-temperature storage. According to the results, the highest weight loss (4.3%), malondialdehyde (MDA (5.8 nmol g⁻¹ FW)), and hydrogen peroxide (H₂O₂ (22.33 nmol g⁻¹ FW)) was detected in control fruit. Fruit firmness was gradually decreased during storage, but it was slower in L-arginine-treated fruit. The highest tissue firmness (3.8 kg cm⁻²) was noted in fruit treated with 0.6 mM L-arginine. The chilling was gradually increased during storage. Fruits treated with L-arginine showed a lower chilling injury than the control fruit. Total soluble tannin compound and antioxidant enzymes activities in persimmons declined during cold storage. L-arginine treatment significantly maintained antioxidant enzymes activity, antioxidant capacity, and total soluble tannin compounds, while L-arginine had no significant impact on titratable acidity and total soluble solids. It seems that a reduction in oxidative damage and an increase in quality of persimmon during low-temperature storage manifested several defense mechanisms induced by exogenous application of L-arginine. These findings indicated that the application of L-arginine to maintain the quality and increase postharvest life of persimmon is very useful and can be applied during cold storage.

Metabolic alterations in alga Chlamydomonas reinhardtii exposed to nTiO2 materials

Nano-sized titanium dioxide (nTiO2) is one of the most commonly used materials, however the knowledge about the molecular basis for metabolic and physiological changes in phytoplankton is yet to be explored. In the present study we use a combination of targeted metabolomics, transcriptomics and physiological response studies to decipher the metabolic perturbation in green alga Chlamydomonas reinhardtii exposed for 72 h to increasing concentrations (2, 20, 100 and 200 mg L-1) of nTiO2 with primary sizes of 5, 15 and 20 nm. Results show that the exposure to all three nTiO2 materials induced perturbation of the metabolism of amino acids, nucleotides, fatty acids, tricarboxylic acids, antioxidants but not in the photosynthesis. The alterations of the most responsive metabolites were concentration and primary size-dependent despite the significant formation of micrometer-size aggregates and their sedimentation. The metabolic perturbations corroborate the observed physiological responses and transcriptomic results and confirmed the importance of oxidative stress as a major toxicity mechanism for nTiO2. Transcriptomics revealed also an important influence of nTiO2 treatments on the transport, adenosine triphosphate binding cassette transporters, and metal transporters, suggesting a perturbation in a global nutrition of the microalgal cell, which was most pronounced for exposure to 5 nm nTiO2. The present study provides for the first-time evidence for the main metabolic perturbations in green alga C. reinhardtii exposed to nTiO2 and helps to improve biological understanding of the molecular basis of these perturbations.

Oxidative Stress Mitigation by Chitosan Nanoparticles in Durum Wheat Also Affects Phytochemicals and Technological Quality of Bran and Semolina

In our previous work, durum wheat cv. Fabulis was grown over two consecutive seasons (2016–2017 and 2017–2018) in an experimental field in the north of Italy. With the aim of mitigating oxidative stress, plants were subjected to four treatments (deionized water, CHT 0.05 mg/mL, CHT-NPs, and CHT-NPs-NAC) three times during the experiment. Chitosan nanoparticles (CHT-NPs) reduced symptom severity on wheat leaves and positively influenced the final grain yield. The present work aimed at investigating whether CHT treatments and particularly N-acetyl cysteine (NAC)-loaded or -unloaded CHT-NPs, while triggering plant defense mechanisms, might also vary the nutritional and technological quality of grains. For this purpose, the grains harvested from the previous experiment were analyzed for their content in phytochemicals and for their technological properties. The results showed that CHT increased the polyphenol and tocopherol content and the reducing capacity of bran and semolina, even if the positive effect of the nano-formulation remained still unclear and slightly varied between the two years of cultivation. The positive effect against oxidative stress induced by the chitosan treatments was more evident in the preservation of both the starch pasting properties and gluten aggregation capacity, indicating that the overall technological quality of semolina was maintained. Our data confirm the role of chitosan as an elicitor of the antioxidant defense system in wheat also at the grain level.

Effects of polystyrene nanoplastics on lead toxicity in dandelion seedlings

Increasing rates of commercialization and industrialization have led to the comprehensive evaluation of toxic effects of microplastics on crop plants. However, research on the impact of functionalized polystyrene nanoplastics on the toxicity of heavy metals remains limited. This study investigated the effects of polystyrene, carboxy-modified polystyrene, and amino-modified polystyrene on lead (Pb) toxicity in dandelion seedlings. The results showed that carboxy -modified polystyrene with a negative charge absorbed more Pb²⁺ than polystyrene and amino-modified polystyrene, and their maximum adsorption amounts were 5.328, 0.247, and 0.153 μg g^-1, respectively. The hydroponic experiment demonstrated that single amino-modified polystyrene was more toxic to dandelion seedlings than polystyrene and carboxy-modified polystyrene. The presence of Pb²⁺ was found to increase antioxidant enzymes (superoxide dismutase and catalase) and non-antioxidant enzymes (glutathione and ascorbic acid) activities in response to excessive reactive oxygen species in dandelion leaves and roots treated with polystyrene and carboxy-modified polystyrene, while it did not change much when amino-modified polystyrene was added. Interestingly, compared with single Pb²⁺, the addition of amino-modified polystyrene with positive charges induced an obvious decrease in the above parameters; however, they declined slightly in the treatments with polystyrene and carboxy-modified polystyrene despite a stronger adsorption capacity for Pb²⁺. Similarly, the bioactive compounds, including flavonoids, polyphenols, and polysaccharides in dandelion, showed a scavenging effect on O₂^- and H₂O₂, thereby inhibiting the accumulation and reducing medicinal properties. This study found that the effects of microplastics on the uptake, distribution, and toxicity of heavy metals depended on the nanoparticle surface charge.

Cell death induced by mycotoxin fumonisin B1 is accompanied by oxidative stress and transcriptional modulation in Arabidopsis cell culture

Fumonisin B₁ induces rapid programmed cell death in Arabidopsis cells, oxidative and nitrosative bursts, and differentially modulates cell death responsive genes. Glutathione is the main antioxidant involved in the stress response. Fumonisin B₁ (FB₁) is a fungal toxin produced by Fusarium spp. able to exert pleiotropic toxicity in plants. FB₁ is known to be a strong inducer of the programmed cell death (PCD); however, the exact mechanism underling the plant-toxin interactions and the molecular events that lead to PCD are still unclear. Therefore, in this work, we provided a comprehensive investigation of the response of the model organism Arabidopsis thaliana at the nuclear, transcriptional, and biochemical level after the treatment with FB₁ at two different concentrations, namely 1 and 5 µM during a time-course of 96 h. FB₁ induced oxidative and nitrosative bursts and a rapid cell death in Arabidopsis cell cultures, which resembled a HR-like PCD event. Different genes involved in the regulation of PCD, antioxidant metabolism, photosynthesis, pathogenesis, and sugar transport were upregulated, especially during the late treatment time and with higher FB₁ concentration. Among the antioxidant enzymes and compounds studied, only glutathione appeared to be highly induced in both treatments, suggesting that it might be an important stress molecule induced during FB₁ exposure. Collectively, these findings highlight the complexity of the signaling network of A. thaliana and provide information for the understanding of the physiological, molecular, and biochemical responses to counteract FB₁-induced toxicity.

Co-evolved plant and blast fungus ascorbate oxidases orchestrate the redox state of host apoplast to modulate rice immunity

Apoplastic ascorbate oxidases (AOs) play a critical role in reactive oxygen species (ROS)-mediated innate host immunity by regulating the apoplast redox state. To date, little is known about how apoplastic effectors of the rice blast fungus Magnaporthe oryzae modulate the apoplast redox state of rice to subvert plant immunity. In this study, we demonstrated that M. oryzae MoAo1 is an AO that plays a role in virulence by modulating the apoplast redox status of rice cells. We showed that MoAo1 inhibits the activity of rice OsAO3 and OsAO4, which also regulate the apoplast redox status and plant immunity. In addition, we found that MoAo1, OsAO3, and OsAO4 all exhibit polymorphic variations whose varied interactions orchestrate pathogen virulence and rice immunity. Taken together, our results reveal a critical role for extracellular redox enzymes during rice blast infection and shed light on the importance of the apoplast redox state and its regulation in plant-pathogen interactions.

Exploring the parameters of central redox hub for screening salinity tolerant rice landraces of coastal Bangladesh

Regulation of oxidative stress towards origin of favorable internal redox cue plays a decisive role in salinity stress acclimation and least studied in rice and hence is the subject of present investigation. Redox landscaping of seedlings of ten experimental land races of rice of coastal Bangladesh grown under post imbibitional salinity stress (PISS) has been done through characterization of ROS-antioxidant interaction dynamics at metabolic interface, transcriptional reprogramming of redox-regulatory genes along with the assessment of biomarkers of oxidative threat for standardizing redox strategies and quality parameters for screening. The results exhibited a strong correlation between salinity induced redox status (pro-oxidant/antioxidant ratio, efficacy of H₂O₂ turnover through integrated RboH-Ascorbate–Glutathione/Catalase pathway and estimation of sensitive redox biomarkers of oxidative deterioration) and germination phenotypes of all landraces of rice. Transcript abundance of the marker genes of the enzymes associated with central antioxidant hub for H₂O₂ processing (CatA, OsAPx2, SodCc2, GRase and RboH) of all experimental landraces of the rice advocate the central role of H₂O₂ turnover dynamics in regulating redox status and salinity tolerance. Landraces suffering greater loss of abilities of decisive regulation of H₂O₂ turnover dynamics exhibited threat on the oxidative windows of the germinating seeds under salinity.

The Response of Thiols to Cadmium Stress in Spinach (Spinacia Oleracea L.)

The aim of this study is to examine the thiol species for the high cadmium (Cd) tolerance of spinach and provide information for the improvement of soil utilization. The spinach was cultured in aqueous solution with concentrations of Cd ranging from 1 to 9 mg/L. The time responses of glutathione (GSH) and phytochelatins (PCs, PC2-PC4) in the tissues of spinach were monitored via HPLC−MS/MS, and the concentrations of Cd in the roots, shoots and leaves were detected by ICP−OES. Data were analyzed via one-way ANOVA and Spearman correlation to assess the relationships among the types of thiols and the changes between types of thiols and Cd. As Cd stress increased, Cd concentrations in tissues also increased. The total thiol contents responded to Cd stresses with correlations r ranging from 0.394 (root), 0.520 (shoot) to 0.771 (leaf) (p < 0.01). GSH and PC3 were dominant on most of the days under Cd stress. The correlation r between improvements in GSH and increments of Cd concentration in roots was −0.808 (p < 0.01), and r between changes in PC3 and changes in Cd concentrations in leaves was −0.503 (p < 0.01). No correlation can be found between GSH and the subtypes of PCs in shoots, but strong positive correlations within the subtypes of PCs. Thiols can be produced in different tissues of spinach, while the shoots are only a transport tissue for GSH.

Effects of Glyphosate-Based Herbicide on Primary Production and Physiological Fitness of the Macroalgae Ulva lactuca

The use of glyphosate-based herbicides (GBHs) worldwide has increased exponentially over the last two decades increasing the environmental risk to marine and coastal habitats. The present study investigated the effects of GBHs at environmentally relevant concentrations (0, 10, 50, 100, 250, and 500 μg·L⁻¹) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems and energy balance) of Ulva lactuca, a cosmopolitan marine macroalgae species. Although GBHs cause deleterious effects such as the inhibition of photosynthetic activity, particularly at 250 μg·L⁻¹, due to the impairment of the electron transport in the chloroplasts, these changes are almost completely reverted at the highest concentration (500 μg·L⁻¹). This could be related to the induction of tolerance mechanisms at a certain threshold or tipping point. While no changes occurred in the energy balance, an increase in the pigment antheraxanthin is observed jointly with an increase in ascorbate peroxidase activity. These mechanisms might have contributed to protecting thylakoids against excess radiation and the increase in reactive oxygen species, associated with stress conditions, as no increase in lipid peroxidation products was observed. Furthermore, changes in the fatty acids profile, usually attributed to the induction of plant stress response mechanisms, demonstrated the high resilience of this macroalgae. Notably, the application of bio-optical tools in ecotoxicology, such as pulse amplitude modulated (PAM) fluorometry and laser-induced fluorescence (LIF), allowed separation of the control samples and those treated by GBHs in different concentrations with a high degree of accuracy, with PAM more accurate in identifying the different treatments.

SK, Sheoran S, K. UB, K. BN, Kumar S, Singh AN, Singh HV. Seed Longevity in Legumes: Deeper Insights Into Mechanisms and Molecular Perspectives

Sustainable agricultural production largely depends upon the viability and longevity of high-quality seeds during storage. Legumes are considered as rich source of dietary protein that helps to ensure nutritional security, but associated with poor seed longevity that hinders their performance and productivity in farmer's fields. Seed longevity is the key determinant to assure proper seed plant value and crop yield. Thus, maintenance of seed longevity during storage is of prime concern and a pre-requisite for enhancing crop productivity of legumes. Seed longevity is significantly correlated with other seed quality parameters such as germination, vigor, viability and seed coat permeability that affect crop growth and development, consequently distressing crop yield. Therefore, information on genetic basis and regulatory networks associated with seed longevity, as well as molecular dissection of traits linked to longevity could help in developing crop varieties with good storability. Keeping this in view, the present review focuses towards highlighting the molecular basis of seed longevity, with special emphasis on candidate genes and proteins associated with seed longevity and their interplay with other quality parameters. Further, an attempt was made to provide information on 3D structures of various genetic loci (genes/proteins) associated to seed longevity that could facilitate in understanding the interactions taking place within the seed at molecular level. This review compiles and provides information on genetic and genomic approaches for the identification of molecular pathways and key players involved in the maintenance of seed longevity in legumes, in a holistic manner. Finally, a hypothetical fast-forward breeding pipeline has been provided, that could assist the breeders to successfully develop varieties with improved seed longevity in legumes.

Physiological and Differential Proteomic Analysis at Seedling Stage by Induction of Heavy-Ion Beam Radiation in Wheat Seeds

Novel genetic variations can be obtained by inducing mutations in the plant which help to achieve novel traits. The useful mutant can be obtained through radiation mutation in a short period which can be used as a new material to produce new varieties with high yield and good quality wheat. In this paper, the proteomic analysis of wheat treated with different doses of ¹²C and ⁷Li ion beam radiation at the seedling stage was carried out through a Tandem Mass Tag (TMT) tagging quantitative proteomic analysis platform based on high-resolution liquid chromatography-mass spectrometry, and the traditional ⁶⁰Co-γ-ray radiation treatment for reference. A total of 4,764 up-regulated and 5,542 down-regulated differentially expressed proteins were identified. These proteins were mainly enriched in the KEGG pathway associated with amino acid metabolism, fatty acid metabolism, carbon metabolism, photosynthesis, signal transduction, protein synthesis, and DNA replication. Functional analysis of the differentially expressed proteins showed that the oxidative defense system in the plant defense system was fully involved in the defense response after ¹²C ion beam and ⁷Li ion beam radiation treatments. Photosynthesis and photorespiration were inhibited after ¹²C ion beam and ⁶⁰Co-γ-ray irradiation treatments, while there was no effect on the plant with ⁷Li ion beam treatment. In addition, the synthesis of biomolecules such as proteins, as well as multiple signal transduction pathways also respond to radiations. Some selected differentially expressed proteins were verified by Parallel Reaction Monitoring (PRM) and qPCR, and the experimental results were consistent with the quantitative results of TMT. The present study shows that the physiological effect of ¹²C ion beam radiation treatment is different as compared to the ⁷Li ion beam, but its similar to the ⁶⁰Co-γ ray depicting a significant effect on the plant by using the same dose. The results of this study will provide a theoretical basis for the application of ¹²C and ⁷Li ion beam radiation in the mutation breeding of wheat and other major crops and promote the development of heavy ion beam radiation mutation breeding technology.

Effect and function of β-N-methylamino-L-alanine in the diatom Phaeodactylum tricornutum

The neurotoxin β-N-methylamino-L-alanine (BMAA) is an environmental factor connected to neurodegenerative diseases. BMAA can be produced by various microorganisms (e.g. bacteria, cyanobacteria, dinoflagellates and diatoms) present in diverse ecosystems. No previous study has revealed the function of BMAA in diatoms. In the present study, we combined physiological data with metabolomic and transcriptional data in order to investigate the effect and function of BMAA in the diatom Phaeodactylum tricornutum. P. tricornutum, exposed to different concentrations of exogenous BMAA, showed concentration dependent responses. When the concentration of supplemented BMAA was sufficient to arrest the growth of P. tricornutum, oxidative stress and obstructed carbon fixation were obtained from the specific metabolite and transcriptional data. Results also indicated increased concentration of intracellular chlorophyll a and alterations in the GS-GOGAT cycle, whereas the urea cycle was suppressed. We therefore conclude that BMAA represents a toxic metabolite able to control the growth of P. tricornutum by triggering oxidative stress, and further influencing photosynthesis and nitrogen metabolisms.

Thiol-based Oxidative Posttranslational Modifications (OxiPTMs) of Plant Proteins

The thiol group of cysteine (Cys) residues, often present in the active center of the protein, is of particular importance to protein function, which is significantly determined by the redox state of a protein's environment. Our knowledge of different thiol-based oxidative posttranslational modifications (oxiPTMs), which compete for specific protein thiol groups, has increased over the last 10 years. The principal oxiPTMs include S-sulfenylation, S-glutathionylation, S-nitrosation, persulfidation, S-cyanylation and S-acylation. The role of each oxiPTM depends on the redox cellular state, which in turn depends on cellular homeostasis under either optimal or stressful conditions. Under such conditions, the metabolism of molecules such as glutathione, NADPH (reduced nicotinamide adenine dinucleotide phosphate), nitric oxide, hydrogen sulfide and hydrogen peroxide can be altered, exacerbated and, consequently, outside the cell's control. This review provides a broad overview of these oxiPTMs under physiological and unfavorable conditions, which can regulate the function of target proteins.

An Enzyme-Free Photoelectrochemical Sensor Platform for Ascorbic Acid Detection in Human Urine

A novel enzyme-free photoelectrochemical (PEC) potential measurement system based on Dy-OSCN was designed for ascorbic acid (AA) detection. The separation and transmission of internal carriers were accelerated and the chemical properties became more stable under light excitation due to the regular microstructure of the prepared Dy-OSCN monocrystal. More importantly, the PEC potential method (OCPT, open circuit potential-time) used in this work was conducive to the reduction of photoelectric corrosion and less interference introduced during the detection process, which effectively ensured the repeatability and stability of the electrode. Under optimal conditions, the monocrystal successfully served as a matrix for the detection of AA, and the prepared PEC sensor exhibited a wide linear range from 7.94 × 10−6 mol/L to 1.113 × 10−2 mol/L and a sensitive detection limit of 3.35 μM. Practical human urine sample analysis further revealed the accuracy and feasibility of the Dy-OSCN-based PEC platform. It is expected that such a PEC sensor would provide a new way for rapid and non-invasive AA level assessment in human body constitution monitoring and lays a foundation for the further development of practical products.

Trehalose: a promising osmo-protectant against salinity stress-physiological and molecular mechanisms and future prospective

Salt stress is one of the leading threats to crop growth and productivity across the globe. Salt stress induces serious alterations in plant physiological, metabolic, biochemical functioning and it also disturbs antioxidant activities, cellular membranes, photosynthetic performance, nutrient uptake and plant water uptake and resulting in a significant reduction in growth and production. The application of osmoprotectants is considered as an important strategy to induce salt tolerance in plants. Trehalose (Tre) has emerged an excellent osmolyte to induce salinity tolerance and it got considerable attention in recent times. Under salinity stress, Tre helps to maintain the membrane integrity, and improves plant water relations, nutrient uptake and reduces the electrolyte leakage and lipid per-oxidation. Tre also improves gas exchange characteristics, protects the photosynthetic apparatus from salinity induced oxidative damages and brings ultra-structure changes in the plant body to induce salinity tolerance. Moreover, Tre also improves antioxidant activities and expression of stress responsive proteins and genes and confers salt tolerance in plants. Additionally, Tre is also involved in signaling association with signaling molecules and phytohormones and resultantly improved the plant performance under salt stress. Thus, it is interesting to understand the role of Tre in mediating the salinity tolerance in plants. Therefore, in this review we have summarized the different physiological and molecular roles of Tre to induce salt tolerance in plants. Moreover, we have also provided the information on Tre cross-talk with various osmolytes and hormones, and its role in stress responsive genes and antioxidant activities. Lastly, we also shed light on research gaps that need to be addressed in future studies. Therefore, this review will help the scientists to learn more about the Tre in changing climate conditions and it will also provide new insights to insights that could be used to develop salinity tolerance in plants.

Cold stratification-induced dormancy removal in apple (Malus domestica Borkh.) seeds is accompanied by an increased glutathione pool in embryonic axes

A reduced form of glutathione (GSH) is an essential metabolite that participates in the control of reactive oxygen species (ROS) levels in cells. GSH plays a pivotal role in seed biology as a modulator of seed viability and germination. The GSH:GSSG ratio and half-cell reduction potential (E_GSSG/2GSH) serve as indicators of the oxidative status in seeds. Apple (Malus domestica Borkh.) seeds are deeply dormant, and this state is removed by long-term cold stratification. The aim of our work was to examine the modification of GSH and GSSG content, GSH:GSSG ratio and E_GSSG/2GSH in the embryonic axes isolated from apple seeds subjected to cold stratification for 7, 14, 21 and 40 d. Our data indicated that cold stratification increased the generation of free radicals in the embryonic axes, which correlated with an alteration in the expression of genes encoding Rboh, particularly RbohC. GSH and GSSG levels increased during prolonged cold stratification of apple seeds. This was accompanied by the modification of glutathione reductase and glutathione peroxidase-like activities, which did not match their transcript levels. The steady-state GSH:GSSG ratio and E_GSSG/2GSH in the axes of embryos subjected to cold stratification indicated no impact of the dormancy removal treatment on apple seed viability. We suggest that the glutathione system is an important component of the redox network and is involved in the management of the seed transition from dormant to nondormant states.

Glutathione contributes to plant defence against parasitic cyst nematodes

Cyst nematodes (CNs) are an important group of root-infecting sedentary endoparasites that severely damage many crop plants worldwide. An infective CN juvenile enters the host's roots and migrates towards the vascular cylinder, where it induces the formation of syncytial feeding cells, which nourish the CN throughout its parasitic stages. Here, we examined the role of glutathione (l-γ-glutamyl-l-cysteinyl-glycine) in Arabidopsis thaliana on infection with the CN Heterodera schachtii. Arabidopsis lines with mutations pad2, cad2, or zir1 in the glutamate-cysteine ligase (GSH1) gene, which encodes the first enzyme in the glutathione biosynthetic pathway, displayed enhanced CN susceptibility, but susceptibility was reduced for rax1, another GSH1 allele. Biochemical analysis revealed differentially altered thiol levels in these mutants that was independent of nematode infection. All glutathione-deficient mutants exhibited impaired activation of defence marker genes as well as genes for biosynthesis of the antimicrobial compound camalexin early in infection. Further analysis revealed a link between glutathione-mediated plant resistance to CN infection and the production of camalexin on nematode infection. These results suggest that glutathione levels affect plant resistance to CN by fine-tuning the balance between the cellular redox environment and the production of compounds related to defence against infection.

Analysis of reduced and oxidized antioxidants in Hevea brasiliensis latex reveals new insights into the regulation of antioxidants in response to harvesting stress and tapping panel dryness

Latex diagnosis (LD) is applied to optimize the natural rubber production and prevent tapping panel dryness (TPD), a physiological syndrome affecting latex production in Hevea brasiliensis. The reduced thiol content (RSH) is one of the biochemical parameters associated with the risk of TPD. However, RSH is difficult to interpret because of the influence of the environment. In order to better understand the regulation of antioxidants and to better interpret RSH, a key parameter of LD, this study analysed in latex both oxidised and reduced forms of ascorbic acid (AsA) and glutathione, and their cofactors as well as other latex diagnosis parameters in response to harvesting stress (tapping and ethephon stimulation) and TPD occurrence. The content of antioxidants in latex had a high variability among five rubber clones. The concentration in AsA was about ten times higher than GSH in laticifer, GSH accounting for about 50% of RSH. For short-term harvesting stress, RSH increased with tapping frequency and ethephon stimulation. TPD is associated with high latex viscosity and bursting of lysosomal particles called lutoids, as well as for several rubber clones with lower RSH and GSH contents. These results suggest that a high level of RSH shows the capacity of laticifer metabolism to cope with harvesting stress, while a drop in RSH is the sign of long stress related to lower metabolic activity and TPD occurrence. RSH remains an essential physiological parameter to prevent TPD when associated with reference data under low and high harvesting stress. This study paves the way to understand the role of AsA and GSH, and carry out genetic studies of antioxidants.

Salt Priming as a Smart Approach to Mitigate Salt Stress in Faba Bean (Vicia faba L.)

The present investigation aims to highlight the role of salt priming in mitigating salt stress on faba bean. In the absence of priming, the results reflected an increase in H2O2 generation and lipid peroxidation in plants subjected to 200 mM salt shock for one week, accompanied by a decline in growth, photosynthetic pigments, and yield. As a defense, the shocked plants showed enhancements in ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), peroxidase (POX), and superoxide dismutase (SOD) activities. Additionally, the salt shock plants revealed a significant increase in phenolics and proline content, as well as an increase in the expression levels of glutathione (GSH) metabolism-related genes (the L-ascorbate peroxidase (L-APX) gene, the spermidine synthase (SPS) gene, the leucyl aminopeptidase (LAP) gene, the aminopeptidase N (AP-N) gene, and the ribonucleo-side-diphosphate reductase subunit M1 (RDS-M) gene). On the other hand, priming with increasing concentrations of NaCl (50–150 mM) exhibited little significant reduction in some growth- and yield-related traits. However, it maintained a permanent alert of plant defense that enhanced the expression of GSH-related genes, proline accumulation, and antioxidant enzymes, establishing a solid defensive front line ameliorating osmotic and oxidative consequences of salt shock and its injurious effect on growth and yield.

Transcriptomic Analysis and the Effect of Maturity Stage on Fruit Quality Reveal the Importance of the L-Galactose Pathway in the Ascorbate Biosynthesis of Hardy Kiwifruit (Actinidia arguta)

Hardy kiwifruit (Actinidia arguta) has recently become popular in fresh markets due to its edible skin and rich nutritional value. In the present study, different harvest stages of two A. arguta cultivars, 'Issai' and 'Ananasnaya' ("Ana"), were chosen for investigating the effects of maturity on the quality of the fruit. Interestingly, Issai contained 3.34 folds higher ascorbic acid (AsA) content than Ana. The HPLC method was used to determine the AsA content of the two varieties and revealed that Issai had the higher content of AsA and DHA. Moreover, RNA sequencing (RNAseq) of the transcriptome-based expression analysis showed that 30 differential genes for ascorbate metabolic pathways were screened in Issai compared to Ana, which had 16 genes down-regulated and 14 genes up-regulated, while compared to the up-regulation of 8 transcripts encoding the key enzymes involved in the L-galactose biosynthesis pathway. Our results suggested that AsA was synthesized mainly through the L-galactose pathway in hardy kiwifruit.

Effect of Different Salts on Nutrients Uptake, Gene Expression, Antioxidant, and Growth Pattern of Selected Rice Genotypes

Climate change leads to soil salinization, and the dynamic scarcity of freshwater has negatively affected crop production worldwide, especially Oryza sativa. The association among ion uptake, gene expression, antioxidant, biomass, and root and shoot development under different salt stress are not fully understood. Many studies are related to the effect of NaCl only. This study used two salts (CaCl₂ and MgCl₂) along with NaCl and analyzed their effects on mineral uptake (macronutrients and micronutrients), gene expression, seed germination, antioxidants, plant growth, and biomass in different rice genotypes. CaCl₂ (up to 200 mM) slightly increased the germination percentage and seedling growth, whereas, 150 mM MgCl₂ in the soil increased the root, shoot length, and fresh and dry weight in cultivars IR 28 and Cheongcheong. All agronomic traits among rice genotypes were drastically reduced by NaCl stress compared to other salts. Different salt stress differentially regulated ion uptake in the roots and shoots among different rice genotypes. Under different salt stress, a consistent decrease in Ca²⁺, Mn²⁺, and Fe²⁺ ions was observed in the roots of Cheongcheong, Nagdong, and IR 28. Similarly, under different salts, the stress in the shoots of Cheongcheong (Ca²⁺, Na⁺, and Zn²⁺) and Nagdong (Ca²⁺, Mg²⁺, Na⁺, and Zn²⁺) and the shoots of IR 28 (Ca²⁺ and Mg²⁺) consistently increased. Under different salts, a salt stress-related gene was expressed differentially in the roots of rice genotypes. However, after 6 and 12 h, there was consistent OsHKT1, OsNHX1, and OsSOS1 gene upregulation in the shoots of Nagdong and roots and shoots of the salt-tolerant cultivar Pokkali. Under different salt stress, glutathione (GSH) content increased in the shoot of IR 28 and Nagdong by NaCl, and MgCl₂ salt, whereas, POD activity increased significantly by CaCl₂ and MgCl₂ in cultivar Cheongcheong and IR 28 shoot. Therefore, this study suggested that Pokkali responded well to NaCl stress only, whereas, the plant molecular breeding lab cultivar Nagdong showed more salt tolerance to different salts (NaCl, CaCl₂, and MgCl₂). This can potentially be used by agriculturists to develop the new salt-tolerant cultivar "Nagdong"-like Pokkali.

ITRAQ-Based Proteomic Analysis of Wheat (Triticum aestivum) Spikes in Response to Tilletia controversa Kühn and Tilletia foetida Kühn Infection, Causal Organisms of Dwarf Bunt and Common Bunt of Wheat

Dwarf bunt and common bunt diseases of wheat are caused by Tilletia controversa Kühn and Tilletia foetida Kühn, respectively, and losses caused by these diseases can reach 70-80% in favourable conditions. T. controversa and T. foetida are fungal pathogens belonging to the Exobasidiomycetes within the basidiomycetous smut fungi (Ustilaginomycotina). In order to illuminate the proteomics differences of wheat spikes after the infection of T. controversa and T. foetida, the isobaric tags for relative and absolute quantification (iTRAQ) technique was used for better clarification. A total of 4553 proteins were differentially detected after T. controversa infection; 4100 were upregulated, and 453 were downregulated. After T. foetida infection, 804 differentially expressed proteins were detected; 447 were upregulated and 357 were downregulated. In-depth data analysis revealed that 44, 50 and 82 proteins after T. controversa and 9, 6 and 16 proteins after T. foetida were differentially expressed, which are antioxidant, plant-pathogen interaction and glutathione proteins, respectively, and 9 proteins showed results consistent with PRM. The top 20 KEGG enrichment pathways were identified after pathogen infection. On the basis of gene ontology, the upregulated proteins were linked with metabolic process, catalytic activity, transferase activity, photosynthetic membrane, extracellular region and oxidoreductase activity. The results expanded our understanding of the proteome in wheat spikes in response to T. controversa and T. foetida infection and provide a basis for further investigation for improving the defense mechanism of the wheat crops.

Unearthing the Alleviatory Mechanisms of Brassinolide in Cold Stress in Rice

Cold stress inhibits rice germination and seedling growth. Brassinolide (BR) plays key roles in plant growth, development, and stress responses. In this study, we explored the underlying mechanisms whereby BR helps alleviate cold stress in rice seedlings. BR application to the growth medium significantly increased seed germination and seedling growth of the early rice cultivar “Zhongzao 39” after three days of cold treatment. Specifically, BR significantly increased soluble protein and soluble sugar contents after three days of cold treatment. Moreover, BR stimulated the activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase; thereby alleviating cold-induced damage and increasing glutathione content and the GSH/GSSG ratio while concomitantly reducing H2O2 content. BR upregulated the expression levels of cold-response-related genes, including OsICE1, OsFer1, OsCOLD1, OsLti6a, OsSODB, OsMyb, and OsTERF2, and downregulated that of OsWRKY45, overall alleviating cold stress symptoms. Thus, BR not only upregulated cellular osmotic content and the antioxidant enzyme system to maintain the physiological balance of reactive oxygen species under cold but, additionally, it regulated the expression of cold-response-related genes to alleviate cold stress symptoms. These results provide a theoretical basis for rice breeding for cold resistance using young seedlings.

Insights into agar and secondary metabolite pathways from the genome of the red alga Gracilaria domingensis (Rhodophyta, Gracilariales)

Gracilariales is a clade of florideophycean red macroalgae known for being the main source of agar. We present a de novo genome assembly and annotation of Gracilaria domingensis, an agarophyte alga with flattened thallus widely distributed along Central and South American Atlantic intertidal zones. In addition to structural analysis, an organizational comparison was done with other Rhodophyta genomes. The nuclear genome has 78 Mbp, with 11,437 predicted coding genes, 4,075 of which did not have hits in sequence databases. We also predicted 1,567 noncoding RNAs, distributed in 14 classes. The plastid and mitochondrion genome structures were also obtained. Genes related to agar synthesis were identified. Genes for type II galactose sulfurylases could not be found. Genes related to ascorbate synthesis were found. These results suggest an intricate connection of cell wall polysaccharide synthesis and the redox systems through the use of L-galactose in Rhodophyta. The genome of G. domingensis should be valuable to phycological and aquacultural research, as it is the first tropical and Western Atlantic red macroalgal genome to be sequenced.

Making plant methane formation visible-Insights from application of 13C-labeled dimethyl sulfoxide

Methane (CH4) formation by vegetation has been studied intensively over the last 15 years. However, reported CH4 emissions vary by several orders of magnitude, thus making global estimates difficult. Moreover, the mechanism(s) for CH4 formation by plants is (are) largely unknown.Here, we introduce a new approach for making CH4 formation by plants clearly visible. By application of 13C-labeled dimethyl sulfoxide (DMSO) onto the leaves of tobacco plants (Nicotiana tabacum) and Chinese silver grass (Miscanthus sinensis) the effect of light and dark conditions on CH4 formation of this pathway was examined by monitoring stable carbon isotope ratios of headspace CH4 (δ13C-CH4 values).Both plant species showed increasing headspace δ13C-CH4 values while exposed to light. Higher light intensities increased CH4 formation rates in N. tabacum but decreased rates for M. sinensis. In the dark no formation of CH4 could be detected for N. tabacum, while M. sinensis still produced ~50% of CH4 compared to that during light exposure.Our findings suggest that CH4 formation is clearly dependent on light conditions and plant species and thus indicate that DMSO is a potential precursor of vegetative CH4. The novel isotope approach has great potential to investigate, at high temporal resolution, physiological, and environmental factors that control pathway-specific CH4 emissions from plants.

Magnetic Biohybrid Robots as Efficient Drug Carrier to Generate Plant Cell Clones

Micro/nanorobots represent a new generation of micromachines that can accomplish various tasks, such as loading and transporting specific targets or pharmaceuticals for a given application. Biohybrid robots consisting of biological cells (bacteria, sperm, and microalgae) combined with inorganic particles to control or propel their movement are of particular interest. The skeleton of these biohybrid robots can be used to load biomolecules. In this work, the authors create biohybrid robots based on tomato plants by coculturing ferromagnetic nanoparticles (Fe₃ O₄ ) with tomato callus cells. The tomato-based biohybrid robots (Tomato-Biobots) containing Fe₃ O₄ nanoparticles  are driven by a transversely rotating magnetic field. In addition, biohybrid robots are used to load vitamin C, to generate clones of tomato cells. It is shown that the presence of Fe₃ O₄  does not affect the growth of tomato callus. This study opens a wide range of possibilities for the use of biohybrid robots@Fe₃ O₄  to deliver conventional agrochemicals, including fertilizers, pesticides, and herbicides, and allows for a gradual and sustained release of nutrients and agrochemicals, leading to precise dosing that reduces the amount of agrochemicals used. This conceptually new type of micromachine with application to plants and agronomy shall find broad use in this field.

Can biochemical traits bridge the gap between genomics and plant performance? A study in rice under drought

The possibility of introducing metabolic/biochemical phenotyping to complement genomics-based predictions in breeding pipelines has been considered for years. Here we examine to what extent and under what environmental conditions metabolic/biochemical traits can effectively contribute to understanding and predicting plant performance. In this study, multivariable statistical models based on flag leaf central metabolism and oxidative stress status were used to predict grain yield (GY) performance for 271 indica rice (Oryza sativa) accessions grown in the field under well-watered and reproductive stage drought conditions. The resulting models displayed significantly higher predictability than multivariable models based on genomic data for the prediction of GY under drought (Q2 = 0.54-0.56 versus 0.35) and for stress-induced GY loss (Q2 = 0.59-0.64 versus 0.03-0.06). Models based on the combined datasets showed predictabilities similar to metabolic/biochemical-based models alone. In contrast to genetic markers, models with enzyme activities and metabolite values also quantitatively integrated the effect of physiological differences such as plant height on GY. The models highlighted antioxidant enzymes of the ascorbate-glutathione cycle and a lipid oxidation stress marker as important predictors of rice GY stability under drought at the reproductive stage, and these stress-related variables were more predictive than leaf central metabolites. These findings provide evidence that metabolic/biochemical traits can integrate dynamic cellular and physiological responses to the environment and can help bridge the gap between the genome and the phenome of crops as predictors of GY performance under drought.

Antioxidant Response during the Kinetics of Anhydrobiosis in Two Eutardigrade Species

Anhydrobiosis, a peculiar adaptive strategy existing in nature, is a reversible capability of organisms to tolerate a severe loss of their body water when their surrounding habitat is drying out. In the anhydrobiotic state, an organism lacks all dynamic features of living beings since an ongoing metabolism is absent. The depletion of water in the anhydrobiotic state increases the ionic concentration and the production of reactive oxygen species (ROS). An imbalance between the increased production of ROS and the limited action of antioxidant defences is a source of biomolecular damage and can lead to oxidative stress. The deleterious effects of oxidative stress were demonstrated in anhydrobiotic unicellular and multicellular organisms, which counteract the effects using efficient antioxidant machinery, mainly represented by ROS scavenger enzymes. To gain insights into the dynamics of antioxidant patterns during the kinetics of the anhydrobiosis of two tardigrade species, Paramacrobiotus spatialis and Acutuncus antarcticus, we investigated the activity of enzymatic antioxidants (catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase) and the amount of non-enzymatic antioxidants (glutathione) in the course of rehydration. In P. spatialis, the activity of catalase increases during dehydration and decreases during rehydration, whereas in A. antarcticus, the activity of superoxide dismutase decreases during desiccation and increases during rehydration. Genomic varieties, different habitats and geographical regions, different diets, and diverse evolutionary lineages may have led to the specialization of antioxidant strategies in the two species.

Dissecting the Molecular Regulation of Natural Variation in Growth and Senescence of Two Eutrema salsugineum Ecotypes

Salt cress (Eutrema salsugineum, aka Thellungiella salsuginea) is an extremophile and a close relative of Arabidopsis thaliana. To understand the mechanism of selection of complex traits under natural variation, we analyzed the physiological and proteomic differences between Shandong (SD) and Xinjiang (XJ) ecotypes. The SD ecotype has dark green leaves, short and flat leaves, and more conspicuous taproots, and the XJ ecotype had greater biomass and showed clear signs of senescence or leaf shedding with age. After 2-DE separation and ESI-MS/MS identification, between 25 and 28 differentially expressed protein spots were identified in shoots and roots, respectively. The proteins identified in shoots are mainly involved in cellular metabolic processes, stress responses, responses to abiotic stimuli, and aging responses, while those identified in roots are mainly involved in small-molecule metabolic processes, oxidation-reduction processes, and responses to abiotic stimuli. Our data revealed the evolutionary differences at the protein level between these two ecotypes. Namely, in the evolution of salt tolerance, the SD ecotype highly expressed some stress-related proteins to structurally adapt to the high salt environment in the Yellow River Delta, whereas the XJ ecotype utilizes the specialized energy metabolism to support this evolution of the short-lived xerophytes in the Xinjiang region.

Identification of Differentially Expressed Genes in Resistant Tetraploid Wheat (Triticum turgidum) under Sitobion avenae (F.) Infestation

The grain aphid Sitobion avenae (Fabricius) is one of the most destructive pests of wheat (Triticum aestivum). Deployment of resistant wheat germplasm appears as an excellent solution for this problem. Elite bread wheat cultivars only have limited resistance to this pest. The present study was carried out to investigate the potential of the tetraploid wheat (Triticum turgidum) variety Lanmai, which showed high resistance to S. avenae at both seedling and adult plant stages, as a source of resistance genes. Based on apterous adult aphids’ fecundity tests and choice bioassays, Lanmai has been shown to display antixenosis and antibiosis. Suppression subtractive hybridization (SSH) was employed to identify and isolate the putative candidate defense genes in Lanmai against S. avenae infestation. A total of 134 expressed sequence tags (ESTs) were identified and categorized based on their putative functions. RT-qPCR analysis of 30 selected genes confirmed their differential expression over time between the resistant wheat variety Lanmai and susceptible wheat variety Polan305 during S. avenae infestation. There were 11 genes related to the photosynthesis process, and only 3 genes showed higher expression in Lanmai than in Polan305 after S. avenae infestation. Gene expression analysis also revealed that Lanmai played a critical role in salicylic acid and jasmonic acid pathways after S. avenae infestation. This study provided further insights into the role of defense signaling networks in wheat resistance to S. avenae and indicates that the resistant tetraploid wheat variety Lanmai may provide a valuable resource for aphid tolerance improvement in wheat.

Exogenous Zeaxanthin Alleviates Low Temperature Combined with Low Light Induced Photosynthesis Inhibition and Oxidative Stress in Pepper (Capsicum annuum L.) Plants

Low temperature combined with low light (LL) affects crop production, especially the yield and quality of peppers, in northwest China during the winter and spring seasons. Zeaxanthin (Z) is a known lipid protectant and active oxygen scavenger. However, whether exogenous Z can mitigate LL-induced inhibition of photosynthesis and oxidative stress in peppers remains unclear. In this study, we investigated the effects of exogenous Z on photosynthesis and the antioxidant machinery of pepper seedlings subject to LL stress. The results showed that the growth and photosynthesis of pepper seedlings were significantly inhibited by LL stress. In addition, the antioxidant machinery was disturbed by the uneven production and elimination of reactive oxygen species (ROS), which resulted in damage to the pepper. For example, membrane lipid peroxidation increased ROS content, and so on. However, exogenous application of Z before LL stress significantly increased the plant height, stem diameter, net photosynthetic rate (Pn), and stomata, which were obviously closed at LL. The activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), mono de-hydroascorbate reductase (MDHAR), de-hydroascorbate reductase (DHAR), ascorbate peroxidase (APX), and ascorbate oxidase (AAO) improved significantly due to the increased expression of CaSOD, CaCAT, CaAPX, CaMDHAR, and CaDHAR. The ascorbic (AsA) and glutathione (GSH) contents and ascorbic/dehydroascorbate (AsA/DHA) and glutathione/oxidized glutathione (GSH/GSSG) ratios also increased significantly, resulting in the effective removal of hydrogen peroxide (H2O2) and superoxide anions (O2•−) caused by LL stress. Thus, pre-treatment with Z significantly reduced ROS accumulation in pepper seedlings under LL stress by enhancing the activity of antioxidant enzymes and accumulation of components of the ascorbate–glutathione (AsA–GSH) cycle and upregulated key genes in the AsA–GSH cycle.

Ectopic expression γ-glutamylcysteine synthetase of Vicia sativa increased cadmium tolerance in Arabidopsis

Glutathione (GSH) is a multifunctional essential biothiol, and its metabolism is important for plant against toxic metals and metalloids. γ-Glutamylcysteine (γ-EC), which is catalyzed by γ-Glutamylcysteine synthetase (γ-ECS), is a rate-limiting intermediate in GSH synthesis. Here, a γ-ECS gene (Vsγ-ECS) from Vicia sativa was cloned, and its function in modulating Cd tolerance was studied. Vsγ-ECS is a chloroplast localization protein, and the expression of Vsγ-ECS was upregulated by Cd stress in root of V. sativa. Heterologous expression of Vsγ-ECS (35S::Vsγ-ECS) in Arabidopsis enhanced the Cd tolerance of plants through improved primary root length, fresh weight, chlorophyll content and low degree of oxidation associated with reduced H₂O₂ and lipid peroxidation. However, the Cd accumulation of Arabidopsis had no effect on Vsγ-ECS overexpression. Further analysis showed that the increased Cd tolerance in 35S::Vsγ-ECS was mainly due to the capacity of increasing GSH synthesis that improved Cd chelation by GSH and phytochelatins (PCs) and alleviated the oxidative stress caused by Cd stress. In summary, a γ-ECS was characterized from V. sativa, and it demonstrated a property for increasing GSH and PC synthesis to protect plants from Cd poisoning.

Investigation of the direct effect of a precision Ascophyllum nodosum biostimulant on nitrogen use efficiency in wheat seedlings

Reduction in the greenhouse gas (GHG) emissions and nitrogen (N) pollution of ground water by improving nitrogen use efficiency (NUE) in crops has become an intensively investigated research topic in pursuit of a more sustainable future. Although, distinct solutions have been proposed there are only a few reports documenting the detailed interplay between observed plant growth dynamics and changes in plant N related transcriptional and biochemical changes. It was previously demonstrated that the application of a formulated biostimulant (PSI-362) derived from Ascophyllum nodosum (ANE) improves N uptake in Arabidopsis thaliana and in barley. In this study, the effect of PSI-362 on the growth dynamics of wheat seedlings was evaluated at different biostimulant and N supplementation rates. Wheat grown on N deficient MS medium was also analysed from the first hour of the treatment until the depletion of the nutrients in the medium 9 days later. During this time the biomass increase measured for PSI-362 treated plants versus untreated controls was associated with increased nitrate uptake, with surplus N assimilated by the biomass in the form of glutamate, glutamine, free amino acids, soluble proteins, and chlorophyll. Phenotypical and biochemical analysis were supported by evaluation of differential expression of genetic markers involved in nitrate perception and transport (TaNRT1.1/NPF6.3), nitrate and nitrite reduction (TaNR1 and TaNiR1) and assimilation (TaGDH2, TaGoGAT, TaGS1). Finally, a comparative analysis of the precision biostimulant PSI-362 and two generic ANEs demonstrated that the NUE effect greatly differs depending on the ANE formulation used.

Understanding paraquat resistance mechanisms in Arabidopsis thaliana to facilitate the development of paraquat-resistant crops

Paraquat (PQ) is the third most used broad-spectrum nonselective herbicide around the globe after glyphosate and glufosinate. Repeated usage and overreliance on this herbicide have resulted in the emergence of PQ-resistant weeds that are a potential hazard to agriculture. It is generally believed that PQ resistance in weeds is due to increased sequestration of the herbicide and its decreased translocation to the target site, as well as an enhanced ability to scavenge reactive oxygen species. However, little is known about the genetic bases and molecular mechanisms of PQ resistance in weeds, and hence no PQ-resistant crops have been developed to date. Forward genetics of the model plant Arabidopsis thaliana has advanced our understanding of the molecular mechanisms of PQ resistance. This review focuses on PQ resistance loci and resistance mechanisms revealed in Arabidopsis and examines the possibility of developing PQ-resistant crops using the elucidated mechanisms.

Antioxidative and osmoprotecting mechanisms in carrot plants tolerant to soil salinity

Soil salinization is a growing problem for agriculture worldwide and carrot is one the most salt-sensitive vegetable species. However, some varieties are capable of withstanding high salt concentrations due to unknown genetic and physiological mechanisms. The aim of this work was to reveal protecting mechanisms against osmotic and ionic stresses that contribute to salt tolerance in carrot. For this purpose, changes in biochemical traits due to soil salinity occurring in the salt-tolerant and salt-sensitive plants were determined. The obtained results showed that the tolerance of the salt-tolerant variety was partially determined constitutively, however, the exposition to saline soil triggered a physiological response that was more evident in the root than in the leaves. The most noticeable changes were the high increase in the content of osmoprotective proline and other low molecular antioxidants such as glutathione and ascorbic acid, and the decrease in the ratio of reduced to oxidized glutathione forms. These changes imply an efficient operation of the ascorbate–glutathione cycle that together with a high activity of antioxidative enzymes such as peroxidases, indicate on the induction of mechanisms associated mainly with protection against excessive reactive oxygen species.