H2O2 Accumulation Research Articles

Diatoms exhibit dynamic chloroplast calcium signals in response to high light and oxidative stress

Abstract Diatoms are a group of silicified algae that play a major role in marine and freshwater ecosystems. Diatom chloroplasts were acquired by secondary endosymbiosis and exhibit important structural and functional differences from the primary plastids of land plants and green algae. Many functions of primary plastids, including photoacclimation and inorganic carbon acquisition, are regulated by calcium-dependent signalling processes. Calcium signalling has also been implicated in the photoprotective responses of diatoms; however, the nature of calcium elevations in diatom chloroplasts and their wider role in cell signalling remains unknown. Using genetically encoded calcium indicators, we find that the diatom Phaeodactylum tricornutum exhibits dynamic calcium elevations within the chloroplast stroma. Stromal calcium ([Ca2+]str) acts independently from the cytosol and is not elevated by stimuli that induce large cytosolic calcium ([Ca2+]cyt) elevations. In contrast, high light and exogenous hydrogen peroxide (H2O2) induce large, sustained [Ca2+]str elevations that are not replicated in the cytosol. Measurements using the fluorescent H2O2 sensor roGFP2-Oxidant Receptor Peroxidase 1 (Orp1) indicate that [Ca2+]str elevations induced by these stimuli correspond to the accumulation of H2O2 in the chloroplast. [Ca2+]str elevations were also induced by adding methyl viologen, which generates superoxide within the chloroplast, and by treatments that disrupt non-photochemical quenching (NPQ). The findings indicate that diatoms generate specific [Ca2+]str elevations in response to high light and oxidative stress that likely modulate the activity of calcium-sensitive components in photoprotection and other regulatory pathways.

Identification of Reactive Oxygen Species Genes Mediating Resistance to Fusarium verticillioides in the Peroxisomes of Sugarcane

Pokkah boeng disease (PBD), which is caused by Fusarium verticillioides, is a major sugarcane disease in Southeast Asian countries. Breeding varieties to become resistant to F. verticillioides is the most effective approach for minimizing the damage caused by PBD, and identifying genes mediating resistance to PBD via molecular techniques is essential. The production of reactive oxygen species (ROSs) is one of a cell’s first responses to pathogenic infections. Plant peroxisomes play roles in several metabolic processes involving ROSs. In this study, seedlings of YT94/128 and GT37 inoculated with F. verticillioides were used to identify PBD resistance genes. The cells showed a high degree of morphological variation, and the cell walls became increasingly degraded as the duration of the infection increased. There was significant variation in H2O2 accumulation over time. Catalase, superoxide dismutase, and peroxidase activities increased in both seedlings. Analysis of differentially expressed genes (DEGs) revealed that peroxidase-metabolism-related genes are mainly involved in matrix protein import and receptor recycling, adenine nucleotide transport, peroxisome division, ROS metabolism, and processes related to peroxisomal membrane proteins. The expression levels of SoCATA1 and SoSOD2A2 gradually decreased after sugarcane infection. F. verticillioides inhibited the expressions of C5YVR0 and C5Z4S4. Sugarcane infection by F. verticillioides disrupts the balance of intracellular ROSs and increases the cell membrane’s lipid peroxidation rate. Defense-related enzymes play a key regulatory role in maintaining a low, healthy level of ROSs. The results of this study enhance our understanding of the mechanism through which peroxisomes mediate the resistance of sugarcane to PBD and provide candidate genes that could be used to breed varieties with improved traits via molecular breeding.

S-nitrosoglutathione reductase disfavors cadmium tolerance in shoots of Arabidopsis

S-nitrosoglutathione reductase (GSNOR) is involved in the response to cadmium (Cd) exposure. In this study, the plants of mutant (gsnor1-3) with lossing-function of- and over-expression (GSNOROE5) of GSNOR were used to clear the role of GSNOR in Cd tolerance. GSNOR activity increased through upregulating the expression of the AtGSNOR gene and protein in Arabidopsis thaliana under Cd stress, which attenuated Cd tolerance. Oxidative damage was more serious in GSNOROE5 and was alleviated in gsnor1-3 under Cd stress, compared with Col-0. Induction of GSNOR facilitated H2O2 accumulation but inhibited catalase (CAT) activity in shoots under Cd stress. This phenotype was eliminated by 3-amino-1,2,4-triazole (3-AT), a CAT inhibitor. In addition, the expressions of AtCAT1 and AtCAT2 were down-regulated with increasing GSNOR activity under Cd stress. This suggested that GSNOR was involved in the accumulation of hydrogen peroxide (H2O2) through regulating CAT expression and activity under Cd exposure. Furthermore, Cd tolerance and CAT activity were improved by spraying S-nitrosoglutathione (GSNO) onto the surface of the leaves. The in vitro activity of CAT increased with GSNO concentration until a GSNO/CAT ratio of 2 was reached. Thus, CAT activity was relative to GSNOR through regulating the expression and S-nitrosylation level of proteins. In summary, the Cd-induced promotion of GSNOR activity aggravated Cd toxicity in plants by mediating H2O2 accumulation controlled by CAT.

Investigating the role of MpAL1 in drought stress responses in Malus prunifolia: Insights into AL gene family functionality

Drought stress significantly impedes apple growth, development, and yield, leading to substantial economic losses within the global apple industry. Malus prunifolia (Mp), a commonly utilized apple rootstock, has shown promise in augmenting cultivated apple resistance to abiotic stress. Although Alfin-like (ALs) proteins have demonstrated pivotal roles in dicotyledonous plants' response to abiotic stresses, knowledge about AL genes in apple rootstocks is limited, and their functions remain largely elusive. In this study, we identified and characterized 10 MpAL gene members in the apple rootstock genome, confirming their localization within the nucleus. Our investigation revealed the significant regulation of MpALs' expression under drought and abscisic acid (ABA) stresses in M. prunifolia. In this study, one of the members, MpAL1, was selected for further exploration in Arabidopsis and apple to explore its potential function in response to drought and ABA stresses. The results showed that overexpression-MpAL1 transgenic apple calli grew significantly better than WT and MpAL1-RNAi lines, which regulates the accumulation of H2O2 and O2- levels. Additionally, transgenic Arabidopsis plants overexpressing MpAL1 exhibited positively regulating anti-oxidant enzymes activities under stress treatments. Further study showed that silencing MpAL1 in apple plants showed obvious chlorosis in leaves, and accumulation of reactive oxygen species under drought stress. Moreover, our detailed analysis established that MpAL1 regulates several drought and ABA-responsive genes, exerting an influence on their expression in transgenic apple. Collectively, our findings identify MpAL1 as a positive regulator that increases drought stress in apple, shedding light on its potential significance in bolstering drought resistance in this fruit crop.

MsFtsH8 Enhances the Tolerance of PEG-Simulated Drought Stress by Boosting Antioxidant Capacity in Medicago sativa L.

Drought is a major abiotic stress that limits the growth and yield of alfalfa, a vital forage legume. The plant metalloproteinase Filamentation temperature-sensitive H (FtsH) is an ATP- and Zn2+-dependent enzyme that plays a significant character in the plant’s response to environmental stress. However, its functional role in drought resistance remains largely unexplored. This study investigates the drought tolerance role of alfalfa MsFtsH8 by analyzing the growth, physiology, and gene expression of overexpressing plants under drought conditions. The results demonstrated that both MsFtsH8-overexpressing Arabidopsis and alfalfa plants exhibited superior growth condition and enhanced membrane stability. The overexpressing alfalfa plants also showed reduced MDA levels, higher proline content, lower H2O2 accumulation, an increased activity of antioxidant-related enzymes (SOD, POD, and CAT) activity, and an elevated expression of antioxidant-related genes. These results indicated that the overexpression of MsFtsH8 enhanced growth, improved osmotic regulation, reduced ROS levels, and increased antioxidative capacity, ultimately leading to greater drought tolerance in alfalfa. Our findings suggest that MsFtsH8 mitigates oxidative damage caused by drought by modulating the plant’s antioxidant system, thus improving drought tolerance in alfalfa. This study provides a molecular basis and candidate genes for enhancing drought resistance in alfalfa through genetic engineering.

Investigating the influence of selenium and epibrassinolide on antioxidant activity, proline accumulation, and protein expression profiles in wheat plants experiencing heat and drought stress.

In the current investigation, the combination of selenium (Se) and epibrassinolide (EBL) exhibited a promising alleviative response against the concurrent stress of heat and drought in wheat plants. The compromised growth and photosynthetic performance of wheat plants under the combined stress of heat and drought were substantially improved with the treatment involving Se and EBL. This improvement was facilitated through the expression of Q9FIE3 and O04939 proteins, along with enhanced antioxidant activities. The heightened levels of antioxidant enzymes and the accumulation of osmoprotectant proline helped mitigate the overaccumulation of reactive oxygen species (ROS), including electrolyte leakage, H2O2 accumulation, and lipid peroxidation, thus conferring tolerance against the combined stress of heat and drought. Studies have demonstrated that Se and EBL can assist wheat plants in recuperating from the adverse effects of heat and drought. As such, they are essential components of sustainable farming methods that aim to increase crop productivity.

Dynamics of Hydrogen Peroxide Accumulation During Tip Growth of Infection Thread in Nodules and Cell Differentiation in Pea (Pisum sativum L.) Symbiotic Nodules.

Hydrogen peroxide (H2O2) in plants is produced in relatively large amounts and plays a universal role in plant defense and physiological responses, including the regulation of growth and development. In the Rhizobium-legume symbiosis, hydrogen peroxide plays an important signaling role throughout the development of this interaction. In the functioning nodule, H2O2 has been shown to be involved in bacterial differentiation into the symbiotic form and in nodule senescence. In this study, the pattern of H2O2 accumulation in pea (Pisum sativum L.) wild-type and mutant nodules blocked at different stages of the infection process was analyzed using a cytochemical reaction with cerium chloride. The observed dynamics of H2O2 deposition in the infection thread walls indicated that the distribution of H2O2 was apparently related to the stiffness of the infection thread wall. The dynamics of H2O2 accumulation was traced, and its patterns in different nodule zones were determined in order to investigate the relationship of H2O2 localization and distribution with the stages of symbiotic nodule development in P. sativum. The patterns of H2O2 localization in different zones of the indeterminate nodule have been partially confirmed by comparative analysis on mutant genotypes.

ZmLSD1 Enhances Salt Tolerance by Regulating the Expression of ZmWRKY29 in Maize.

Salt stress significantly impairs plant growth, presenting a challenge to agricultural productivity. Exploring the regulatory mechanisms underlying salt stress responses is critically important. Here, we identified a significant role for the maize LESION-SIMULATING DISEASE transcription factor, ZmLSD1, in enhancing salt stress response. Subcellular localization analysis indicated that ZmLSD1-GFP was localized in the nucleus in the maize protoplast. Overexpressing ZmLSD1 in maize obviously enhanced the tolerance of plants to salt stress. Physiological analysis indicated that overexpressed ZmLSD1 in maize could mitigate the accumulation of H2O2 and MDA content exposed to salt stress. RNA-seq and qPCR-PCR analyses showed that ZmLSD1 positively regulated ZmWRKY29 expression. ChIP-qPCR and EMSA experiments demonstrated that ZmLSD1 could directly bind to the promoter of ZmWRKY29 through the GTAC motif both in vitro and in vivo. Overall, our findings suggest that ZmLSD1 plays a positive role in enhancing the tolerance of maize to salt by affecting ZmWRKY29 expression.

Hydrogen peroxide participates in leaf senescence by inhibiting CHLI1 activity.

Hydrogen peroxide promoted leaf senescence by sulfenylating the magnesium chelating protease I subunit (CHLI1) in the chlorophyll synthesis pathway, and inhibited its activity to reduce chlorophyll synthesis. Leaf senescence is the final and crucial stage of plant growth and development, during which chlorophyll experiences varying degrees of destruction. It is well-known that the higher ROS accumulation is a key factor for leaf senescence, but whether and how ROS regulates chlorophyll synthesis in the process are unknown. Here, we report that H2O2 inhibits chlorophyll synthesis during leaf senescence via the I subunit of magnesium-chelatase (CHLI1). During leaf senescence, the decrease of chlorophyll content is accompanied by the increase of H2O2 accumulation, as well as the inhibition of catalase (CAT) genes expression. The mutant cat2-1, with increased H2O2 shows an accelerated senescence phenotype and decreased CHLI1 activity compared with the wild type. H2O2 inhibits CHLI1 activity by sulfenylating CHLI1 during leaf senescence. Consistent with this, the chli1 knockout mutant displays the same premature leaf senescence symptom as cat2-1, while overexpression of CHLI1 in cat2-1 can partially restore its early senescence phenotype. Taken together, these results illustrate that CAT2-mediated H2O2 accumulation during leaf senescence represses chlorophyll synthesis through sulfenylating CHLI1, and thus inhibits its activity, providing a new insight into the pivotal role of chlorophyll synthesis as a participant in orchestrating the leaf senescence.

Employing Titanium Dioxide Nanoparticles as Biostimulant against Salinity: Improving Antioxidative Defense and Reactive Oxygen Species Balancing in Eggplant Seedlings.

Salinity is a major abiotic stress that affects the agricultural sector and poses a significant threat to sustainable crop production. Nanoparticles (NPs) act as biostimulants and significantly mitigate abiotic stress. In this context, this experiment was designed to assess the effects of foliar application of titanium dioxide (TiO2) nanoparticles at 200 and 400 ppm on the growth of eggplant (Solanum melongena) seedlings under moderate (75 mM) and high (150 mM) salinity stress. The TiO2-NPs employed were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) analysis. The seedlings were assessed physiologically, growth-wise, and biochemically. The seedlings were significantly affected by their physiological attributes (Fv'/Fm', Fv/Fm, NPQ), growth (root length, shoot length, number of leaves, fresh biomass, dry biomass, leaf greenness), antioxidative enzymes (SOD, POD, CAT, APx, GR), stress indicators (H2O2, MDA), and toxic ion (Na+) concentrations. The maximum decrease in physiological and growth attributes in eggplant seedling leaves was observed with no TiO2-NP application at 150 mM NaCl. Applying TiO2-NPs at 200 ppm showed significantly less decrease in Fv'/Fm', root length, shoot length, number of leaves, fresh biomass, dry biomass, and leaf greenness. In contrast, there were larger increases in SOD, POD, CAT, APx, GR, and TSP. This led to less accumulation of H2O2, MDA, and Na+. No significant difference was observed in higher concentrations of TiO2-NPs compared to the control. Therefore, TiO2-NPs at 200 ppm might be used to grow eggplant seedlings at moderate and high salinity.

Enhancement of Growth and Lipid Production in Microalgae Using Aggregation-Induced Emission Based Luminescent Material for Sustainable Food and Fuel.

AIEbased nanomaterials are progressively gaining momentum owing to their evolvement into an interdisciplinary field ranging from biomass and biomolecule yield to image-guided photodynamic therapy. This study focuses on a novel strategy to enhance growth, lipid accumulation, and in vivo fluorescence visualisation in green microalgae Chlamydomonas reinhardtii using AIE nanoparticles to quantify radical changes. The absorption of AIE photosensitiser, TTMN was recorded from 420 to 570 nm with a peak at 500 nm, and the emission ranged from 550 to 800 nm with a peak at 650 nm. As a ROSmolecule, H2O2 generation of TTMN in C. reinhardtii cells was detected with AIE nanoprobes TPE-BO. H2O2 accumulation increased with the increase of TTMN concentrations. The maximum growth was observed at 10 µM TTMN-exposed C. reinhardtii cells. Significant lipid accumulation was found in both 10 and 15 µM TTMN-treated cells. For lipid visualisation, an AIE nanoprobe, 2-DPAN was used, and superior fluorescence was determined and compared with the traditional BODIPY dye. Cytotoxicity analysis of 10 µM TTMN on the HaCat cell line with 86.2% cell viability revealed its high biocompatibility on living cells. This AIE-based nanotechnology provides a novel approach for microalgae-derived sustainable biomass and eco-friendly biofuel production.

From landraces to haplotypes, exploiting a genomic and phenomic approach to identify heat tolerant genotypes within durum wheat landraces

Dry and hot climates severely impact wheat yields, necessitating the development of innovative solutions to accelerate the breeding and selection of more adaptable durum wheat genotypes. The aim of this study was to identify new wheat ecotypes that can bridge the gap between commercial varieties and adaptability to ongoing climate change. In this study, advanced genomic and phenomic techniques were combined to characterize a set of durum wheat landraces derived from single seed descent (SSD). This approach enabled the identification of novel variability in the TdHsp26-A1 and -B1 genes. As a result, 38 durum wheat genotypes were analyzed using targeted enrichment PCR, leading to the identification of 17 novel haplotype combinations with SNPs in the TdHsp26 genes. The response of these SSD haplotypes to heat stress was characterized at both the seedling and tillering growth stages. Phenotypic analysis of contrasting genotypes led to the selection of two distinct genotypes: SSD69 and SSD397. During heat stress, SSD69 exhibited altered accumulation of H2O2 and MDA content under both growth conditions, providing new insights into the oxidative response to heat stress. Additionally, this work identifies phenotypic traits that are suitable for detecting differences between variants. The geographic distribution of the different alleles aligned with the spread of durum wheat from its center of origin.

Shattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodes.

It is generally accepted that for safe use of neural interface electrodes, irreversible faradaic reactions should be avoided in favor of capacitive charge injection. However, in some cases, faradaic reactions can be desirable for controlling specific (electro)physiological outcomes or for biosensing purposes. This study aims to systematically map the basic faradaic reactions occurring at bioelectronic electrode interfaces. We analyze archetypical platinum-iridium (PtIr), the most commonly used electrode material in biomedical implants. By providing a detailed guide to these reactions and the factors that influence them, we offer a valuable resource for researchers seeking to suppress or exploit faradaic reactions in various electrode materials. We employed a combination of electrochemical techniques and direct quantification methods, including amperometric, potentiometric, and spectrophotometric assays, to measure O2, H2, pH, H2O2, Cl2/OCl-, and soluble platinum and iridium ions. We compared phosphate-buffered saline (PBS) with an unbuffered electrolyte and complex cell culture media containing proteins. Our results reveal that the "water window"─the potential range without significant water electrolysis─varies depending on the electrolyte used. In the culture medium that is rich with redox-active species, a window of potentials where no faradaic process occurs essentially does not exist. Under cathodic polarizations, significant pH increases (alkalization) were observed, while anodic water splitting competes with other processes in media, preventing prevalent acidification. We quantified the oxygen reduction reaction and accumulation of H2O2 as a byproduct. PtIr efficiently deoxygenates the electrolyte under low cathodic polarizations, generating local hypoxia. Under anodic polarizations, chloride oxidation competes with oxygen evolution, producing relatively high and cytotoxic concentrations of hypochlorite (OCl-) under certain conditions. These oxidative processes occur alongside PtIr dissolution through the formation of soluble salts. Our findings indicate that the conventional understanding of the water window is an oversimplification. Important faradaic reactions, such as oxygen reduction and chloride oxidation, occur within or near the edges of the water window. Furthermore, the definition of the water window significantly depends on the electrolyte composition, with PBS yielding different results compared with culture media.

CNGC20 plays dual roles in regulating plant growth and immunity in Brassica napus

Inflorescence architecture is determined by inflorescence length, branch angles and the density of siliques, which affects planting density, lodging resistance and mechanical operation in rapeseed. However, the molecular mechanisms controlling inflorescence architecture are poorly understood, restricting the progress of breeding varieties with ideal plant architecture in oilseed rape. In this study, we have identified and characterized a rapeseed inflorescence development mutant, reduced inflorescence length (ril), which exhibits determinate and shortened inflorescences, reduced plant height, compact branches, and increased silique density. Through BSA-seq and map-based cloning, we find that RIL encodes a cyclic nucleotide-gated channel 20 (BnaA01.CNGC20). A substitution of proline at the 304th position to leucine (P304L) was identified in the conserved transmembrane domain of BnaA01.CNGC20. This P304L substitution neither affects the subcellular localization and self-assembly of BnaA01.CNGC20, nor disrupts the interactions with BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase 1 (BAK1), which interacts with CNGC20 and phosphorylates it to regulate Ca2+ channel stability. However, the P304L substitution increases channel activity and Ca2+ influx, which in turn induces immune responses such as cell death, H2O2 accumulation, upregulation of pathogenesis-related genes, and pattern-triggered immunity. The enhanced immunity improves the resistance to Leptosphaeria biglobosa and Sclerotinia sclerotiorum. Transcriptome analysis further revealed that CNGC20 plays dual roles in regulating plant growth and immunity via the brassinosteroid and auxin signaling pathways. The findings in this study provide deeper insights into the intricate relationship between cytosolic Ca2+ level and plant development and immunity, as well as the trade-off between immunity and the performance of yield-related traits in the heterozygous plants (+/ril), which may serve as a guide for balancing yield and disease resistance in oilseed rape breeding.

The transcription factor ZmNAC84 increases maize salt tolerance by regulating ZmCAT1 expression

Salt stress severely affects plant growth and yield. The transcription factor NAC plays a variety of important roles in plant abiotic stress, but we know relatively little about the specific molecular mechanisms of NAC in antioxidant defense. Here, our genetic studies reveal the positive regulation of salt tolerance in maize by the transcription factor ZmNAC84. Under salt stress, overexpression of ZmNAC84 in maize increased the expression of ZmCAT1, enhanced CAT activity, and consequently reduced H2O2 accumulation, thereby improving salt stress tolerance in maize. Whereas RNA interference-mediated knockdown of ZmNAC84 produced the opposite effect. Subsequently, we found that ZmNAC84 directly binds to and regulates the expression of the ZmCAT1 promoter, and the hybridized material also demonstrated that ZmCAT1 is a downstream target gene of ZmNAC84. In addition, phenotypic and biochemical analyses indicated that ZmCAT1 positively regulated salt tolerance by regulating H2O2 accumulation under salt stress. Taken together, these results reveal the function of ZmNAC84 in regulating ZmCAT1-mediated antioxidant defense in response to salt stress in plants.

Tripartite interactions between grapevine, viruses, and arbuscular mycorrhizal fungi provide insights into modulation of oxidative stress responses

Arbuscular mycorrhizal fungi (AMF) can be beneficial for plants exposed to abiotic and biotic stressors. Although widely present in agroecosystems, AMF influence on crop responses to virus infection is underexplored, particularly in woody plant species such as grapevine. Here, a two-year greenhouse experiment was set up to test the hypothesis that AMF alleviate virus-induced oxidative stress in grapevine. The ‘Merlot’ cultivar was infected with three grapevine-associated viruses and subsequently colonized with two AMF inocula, containing one or three species, respectively. Five and fifteen months after AMF inoculation, lipid peroxidation - LPO as an indicator of oxidative stress and indicators of antioxidative response (proline, ascorbate - AsA, superoxide dismutase - SOD, ascorbate- APX and guaiacol peroxidases - GPOD, polyphenol oxidase - PPO, glutathione reductase - GR) were analysed. Expression of genes coding for a stilbene synthase (STS1), an enhanced disease susceptibility (EDS1) and a lipoxygenase (LOX) were determined in the second harvesting. AMF induced reduction of AsA and SOD over both years, which, combined with not AMF-triggered APX and GR, suggests decreased activation of the ascorbate-glutathione cycle. In the mature phase of the AM symbiosis establishment GPOD emerged as an important mechanism for scavenging H2O2 accumulation. These results, together with reduction in STS1 and increase in EDS1 gene expression, suggest more efficient reactive oxygen species scavenging in plants inoculated with AMF. Composition of AMF inocula was important for proline accumulation. Overall, our study improves the knowledge on ubiquitous grapevine-virus-AMF systems in the field, highlighting that established functional AM symbiosis could reduce virus-induced stress.

Ethylene and hydrogen sulfide regulate hexavalent chromium toxicity in two pulse crops: Implication on growth, photosynthetic activity, oxidative stress and ascorbate glutathione cycle

Sustainable agriculture has become prime importance to feed growing population. To achieve this goal application of exogenous hormones and signaling molecules are gaining important. In this context, we have investigated potential of ethylene (25 μM ethephon; donor) and H2S (10 μM NaHS; donor) in mitigating hexavalent chromium [Cr (VI), 50 μM] toxicity in two pulse seedlings: black bean and mung bean. Cr(VI) declined growth and gas exchange parameters (photosynthetic rate, stomatal conductance, sub cellular CO2 concentration, and transpiration level) which was accompanied by intracellular accumulation of Cr in both pulse crops and the damaging effect was greater in mung bean seedlings. The suppression in the growth and related parameters was occurred due to higher buildup of oxidative stress markers; O2•‾, H2O2, lipid peroxidation (as malondialdehyde, MDA equivalents) and membrane injury in leaf and root of both pulse crops. Cr induced disturbance in AsA-GSH cycle (reduction in the activity of glutathione reductase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase, and the amount of ASA and GSH) could be one of the reasons for greater accumulation of H2O2. Further, exogenous application of ethylene and H2S significantly ameliorated Cr toxicity on growth and photosynthetic activity by significantly lowering the intracellular Cr accumulation and oxidative biomarkers, and also by strengthening the activity of AsA-GSH cycle. The exogenous application of biosynthesis inhibitors of ethylene (AVG) and H2S (PAG) caused greater damaging effect on these parameters due to more accumulation of Cr(VI), thereby suggesting that the endogenous levels of these regulators are critical for Cr(VI) tolerance. Interestingly, ET did not rescue adverse effects of Cr(VI) in absence of endogenous H2S, while H2S could do so even without endogenous ethylene, suggesting that H2S played downstream signaling to ethylene in regulating Cr(VI) toxicity. Hence, being cheap and easily available theses growth regulators may be considered for sustainable agriculture.

Drought and heat stress interactions modify photorespiration and hydrogen peroxide content in Silver fir.

Photorespiration (PR) greatly reduces net carbon assimilation in trees (by c. 25%), but has received recent attention particular for its potential role in stress-signaling through the accumulation of hydrogen peroxide (H2O2), a stress signaling agent. Despite an increasing frequency of drought and heat events affecting forests worldwide, little is known about how concurrent abiotic stressors may interact to affect PR and subsequent H2O2 accumulation in trees. Here, we sought to identify how drought and a compounded one-day heat treatment individually and interactively affect PR (determined under variable O2) in Abies alba Mill. seedlings. Additionally, we quantified foliar H2O2 accumulation and enzymatic scavenging via peroxidase in relation to PR rates. We found drought stress to slightly increase PR (+5.2%) during mild-drought (12 days, Ψmd = -0.85 MPa), but ultimately to decrease PR (-13.6%) during severe-drought (26 days, Ψmd = -1.70 MPa) compared to the control, corresponding to increasing non-stomatal limitations of photosynthesis (i.e., decreased electron transport rate). The response of PR to heat stress was dependent on soil water availability as heat stress increased PR in control seedlings (+37.8%), but not in drought-stressed seedlings. Decreased PR during severe-drought corresponded to ~2x lower foliar H2O2 compared to the control. Despite increased PR under heat stress in control seedlings, foliar H2O2 decreased to near-zero likely due to enhanced scavenging as observed in ~2x greater peroxidase activity. Our results demonstrate that carbon loss to PR during drought stress can be highly dynamic, depending on the severity of soil dehydration. Additionally, increased PR under abiotic stress does not necessarily lead to accumulated H2O2, as tight regulation by scavenging enzymes instead minimize oxidative stress, reducing stress-signaling potential.

Exogenous deferoxamine mesylate suppresses iron-dependent ferroptosis in postharvest fruit rot of blueberry caused by Alternaria alternata and Fusarium fujikuroi

Plant development relies heavily on regulated cell death, which is crucial for specific plant responses to biological stresses. Ferroptosis, an iron-dependent, oxidative, and non-apoptotic cell death form, has been recently discovered in animal cells. In this study, we investigated whether a ferroptosis-like process could be relevant to cell death in postharvest fruit rot of blueberry caused by Alternaria alternata and Fusarium fujikuroi. The results showed that deferoxamine mesylate and glutathione (GSH) treated fruit showed enhanced disease resistance with lower lesion areas, whereas an opposite result was observed in hydrogen peroxide (H2O2) treatment, indicating that intracellular ferroptosis might exist in the fungal infected blueberry fruit. Compared to control, deferoxamine mesylate or GSH treatment improved chlorophyll fluorescence parameters, which contributed to the stability of photosynthesis. In terms of ferroptosis pathway in the adjacent area of infected fruit, deferoxamine mesylate suppressed an iron-dependent cell death pathway that was characterized by depletion of H2O2 and MDA and accumulation of GSH, as well as the reduction of ferrous ions and total iron ions. Meanwhile, deferoxamine mesylate could effectively delay the decrease rate of unsaturation value and key phospholipids of fungi infected fruit during storage, which possibly maintained the integrity of cell membrane. Due to the serious rot of the lesion area, the peroxidation of membrane lipids was severe, accompanied by metabolic disorders. These combined results demonstrated that deferoxamine mesylate treatment could reduce Fenton reaction by chelating Fe2+ and avoid excessive accumulation of reactive oxygen species (ROS), suppress iron-dependent ferroptosis, thereby maintaining fruit quality and reducing postharvest diseases.

Cobalt stress enhanced dendrobine-type total alkaloids biosynthesis of Trichoderma longibrachiatum UN32 through reactive oxygen species formation.

Trichoderma longibrachiatum UN32 is a well-documented mutant strain known to produce dendrobine-type total alkaloids (DTTAs). It was serendipitously observed that the addition of Co2+ to the medium resulted in a notable enhancement in DTTAs production in the T. longibrachiatum UN32 strain, accompanied by an upregulating effect on the expression of antioxidase-related genes. Hence, the objective of the present work was to ascertain whether ROS (intracellular levels of hydrogen peroxide) induced by Co2+ treatment has a beneficial or detrimental impact on DTTAs biosynthesis. A comparison of the intracellular levels of hydrogen peroxide (H2O2) and DTTAs treated with CoCl2 and CH3COOH revealed that CoCl2 was the optimal inducer for investigating the relationship between ROS formation and DTTAs production. This was due to the observation that ROS formation was reduced by approximately 4% and DTTAs production was increased by 12.55% in comparison to the CH3COOH treatment. The physiological results revealed that the introduction of Co2+ resulted in the oxidative damage and activation of the expression of intracellular superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Furthermore, it was confirmed that ROS induced by Co2+ was beneficial to DTTAs production by adding exogenous ROS scavengers. The inclusion of all ROS scavengers, including vitamin C, tocopherol, melatonin, mannitol, and sesamol, resulted in a reduction in ROS accumulation and a concomitant decrease in DTTAs production. Specifically, the addition of melatonin at a concentration of 0.4mg/L demonstrated significant effects, resulting in a 32.53% (P < 0.01) decrease in ROS accumulation and a 45.22% (P < 0.01) reduction in DTTAs production. Subsequently, the timelines of accumulation of intracellular H2O2 and DTTAs content indicated that ROS are also crucial for normal fermentation without CoCl2 addition. Specifically, the proper H2O2 dose for DTTAs accumulation is between 8.82 and 18.86μmol/g. The present study offers the initial experimental evidence indicating that CoCl2 enhance DTTAs production during the culture of T. longibrachiatum UN32 via leading an increase in intracellular ROS, which is conductive to DTTAs production and can be inhibited by the ROS scavengers. Our results provide insights into the mechanistic study of DTTAs biosynthesis.