Ascorbate Peroxidase Research Articles

Salicylic Acid Treatment Ameliorates Postharvest Quality Deterioration in 'France' Prune (Prunus domestica L. 'Ximei') Fruit by Modulating the Antioxidant System.

The potential of salicylic acid (SA) in delaying postharvest fruit senescence has been extensively documented; nevertheless, its effect on antioxidant activity and quality of 'France' prune fruit is largely unknown. The study investigated the effects of SA (0.5 mM) on postharvest quality deterioration of 'France' prune fruit. Results indicated that SA impeded the increase in respiration rate and weight loss, and mitigated the decrease of soluble solids content (SSC), titratable acidity (TA) content, firmness, and hue angle. SA sustained the ascorbate-glutathione cycle by inducing the production of ascorbic acid (AsA) and glutathione (GSH) and attenuates flavonoids, total phenols, and anthocyanins degradation by inhibiting polyphenol oxidase (PPO) activity and PdPPO. Moreover, SA significantly improved superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), and glutathione reductase (GR) activities and gene expression levels, sustained higher 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging capacity, ferric reducing antioxidant power (FRAP), and hydroxyl radical (·OH) inhibition capacity, and impeded the production of hydrogen peroxide (H2O2) and superoxide anion (O2•-). Overall, SA improved the antioxidant capacity by inducing the synthesis of defense response-related substances and promoting antioxidant enzyme activities to sustain the storage quality of 'France' prune fruit.

Exploring the phytoremediation capacity of Portulaca oleracea naphthalene aromatic hydrocarbon contaminants: a physiological and biochemical study.

This study is aimed to explore the potential of purslane (Portulaca oleracea L.) as a phytoremediation candidate for the removal of naphthalene in a hydroponic system; moreover, the impacts of naphthalene on the physiological and biochemical characteristics of the plant were investigated. Four different naphthalene concentrations (0, 15, 30, and 60ppm) were selected for the experiments, with an additional control treatment without plants containing 60ppm naphthalene. Each treatment, utilizing a total of 20 hydroponic containers, consisted of 4 replicates. The results indicated that naphthalene led to a reduction in root and shoot growth. The root weight decreased from 17mg in the control group to 6mg in the 60ppm naphthalene treatment, while the shoot weight decreased from 107.5mg in the control group to 65.7mg in the 60ppm naphthalene treatment. Besides, the different naphthalene concentrations had an impact on the photosynthetic pigments. Compared to the control treatment, under severe stress conditions, chlorophyll a decreased by 51.85%, chlorophyll b decreased by 48.14%, and carotenoids decreased by 54.59%; however, anthocyanin, compared to the control treatment, increased by 30.1% under severe stress conditions. The presence of naphthalene also resulted in increased levels of malondialdehyde, hydrogen peroxide, and proline in both roots and shoots at various naphthalene concentrations. In roots, malondialdehyde increased by 40.74%, H2O2 increased by 3%, and proline increased by 75.6%, while malondialdehyde increased by 43.16%, H2O2 increased by 5.34%, and proline increased by 59.48% in shoots under severe stress conditions and compared to the control treatment. Root and shoot protein levels decreased by 64.49% and 32.26%, respectively. Furthermore, the antioxidant enzymes of glutathione S-transferase, superoxide dismutase, catalase, and ascorbate peroxidase showed increased activities in both roots and shoots under severe naphthalene stress conditions. Purslane demonstrated the ability to remove approximately 80% of naphthalene from the medium. In conclusion, this plant has an effective participation in naphthalene uptake and mitigates the adverse effects of naphthalene by enhancing antioxidant enzyme and proline activities.

Overexpression of rice lectin receptor-like kinase, OsLec-RLK, confers salinity stress tolerance and increases seed yield in pigeon pea (Cajanus cajan (L.) Millsp.).

OsLec-RLK overexpression enhances cell signalling and salt stress tolerance in pigeon pea, enhancing seed yield and harvest index and thus, enabling marginal lands to increase food and nutritional security. Lectin Receptor-like kinases (Lec-RLKs) are highly effective cell signaling molecules that counteract various stresses, including salt stress. We engineered pigeon pea by overexpressing OsLec-RLK gene for enhancing salt tolerance. The OsLec-RLK overexpression lines demonstrated superior performance under salt stress, from vegetative to reproductive phase, compared to wild types (WT). The overexpression lines had significantly higher K+/Na+ratio than WT exposed to 100mM NaCl. Under salt stress, transgenic lines showed higher levels of chlorophyll, proline, total soluble sugars, relative water content, and peroxidase and catalase activity than WT plants. Membrane injury index and lipid peroxidation were significantly reduced in transgenic lines. Analysis of phenological and yield attributes confirmed that the OsLec-RLK pigeon pea lines maintain plant vigor, with 10.34-fold increase in seed yield (per plant) and 4-5-fold increase in harvest index of overexpression lines, compared to wild type. Meanwhile, the overexpression ofOsLec-RLK up-regulated the expression levels ofhistone deacetylase1, acyl CoA, ascorbate peroxidase, peroxidase, glutathione reductase and catalase, which were involved in the K+/Na+homeostasis pathway. This study showed the potential of OsLec-RLK gene for increasing crop productivity and yields under salt stress and enabling the crops to be grown on marginal lands for increasing food and nutritional security.

Exogenous Melatonin Alleviates Osmotic Stress by Enhancing Antioxidant Metabolism, Photosynthetic Maintenance, and Hormone Homeostasis in Forage Oat (Avena sativa) Seedlings

Melatonin (MT) is a multifunctional hormone that enhances crop resilience against various abiotic stresses. However, its regulatory mechanism of osmotic tolerance in forage oats (Avena sativa) plants under water-limited scenarios is still unclear. This study aimed to delineate the impact of MT pretreatment on the morphological, physiological, and biochemical functions of oat seedlings under osmotic stress. Our findings demonstrated that exogenous treatment of MT noticeably elevated leaf area while decreasing the root/shoot ratio of oat seedlings subjected to osmotic stress. Osmotic-induced 38.22% or 48.37% decrease in relative water content could be significantly alleviated by MT pretreatment on day 7 or day 14, respectively. MT treatment also significantly mitigated osmotic-induced decreases in photosynthetic parameters including net photosynthetic rate, stomatic conductance, and intercellular CO2 concentration as well as various chlorophyll fluorescence parameters, which could contribute to enhanced accumulations of free proline and soluble sugars in seedlings after being subjected to a prolonged duration of osmotic stress. Furthermore, MT markedly improved antioxidant enzyme activities including superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase along with the accumulation of ascorbic acid contributing to a significant reduction in reactive oxygen species under osmotic stress. In addition, the MT application induced a 978.12%, 33.54%, or 30.59% increase in endogenous MT, indole acetic acid, or gibberellic acid content under osmotic stress but did not affect the accumulation of abscisic acid. These findings suggest that an optimal concentration of MT (100 μmol·L−1) could relieve osmotic stress via improvement in osmotic adjustment, the enzymatic antioxidant defense system, and endogenous hormonal balance, thereby contributing to enhanced photosynthetic functions and growth of oat seedlings under water-limited conditions.

Unravelling the role of proline in glyphosate-mediated toxicity - tolerance mechanism or stress signal?

Glyphosate (GLY), the most widely used herbicide, has been regarded as an emergent environmental contaminant due to its constant and cumulative use, with potential harm to non-target organisms, such as crops, disrupting cells' redox balance. Therefore, plants need to fine-tune their antioxidant (AOX) mechanisms to thrive under GLY-contaminated environments. Proline overaccumulation is a common response in plants exposed to GLY, yet its role in GLY-induced toxicity remains unclear. Thus, this study explores whether Pro overaccumulation in response to GLY is perceived as a downstream tolerance mechanism or an early-warning stress signal. To investigate this, Arabidopsis thaliana T-DNA mutant lines for Pro biosynthetic (P5CS1) and catabolic genes (ProDH) were used and screened for their GLY susceptibility. Upon seedlings' exposure to GLY (0.75 mg L-1) for 14 days, the herbicide led to reduced biomass in all genotypes, accompanied by Pro overaccumulation. Mutants with heightened Pro levels (prodh) exhibited the greatest biomass reduction, increased lipid peroxidation (LP), and hydrogen peroxide (H2O2) levels, accompanied by a compromised performance of the AOX system. Conversely, p5cs1-4, mutants with lower Pro levels, demonstrated an enhanced AOX system activation, not only with increased levels of glutathione (GSH) and ascorbate (AsA), but also with increased activity of both ascorbate peroxidase (APX) and catalase (CAT). These findings suggest that Pro overaccumulation under GLY exposure is associated with stress sensitivity rather than tolerance, highlighting its potential as an early-warning signal for GLY toxicity in non-target plants and for detecting weed resistance.

Melatonin Prolongs the Postharvest Storability of Strawberry Fruits through Reduced Oxidative Stress and Improved Enzyme Activity

Strawberry fruits are popular among consumers because of their unique flavor and reported health benefits. However, microbial growth and oxidative stress that occur in postharvest storage cause strawberry fruits to have a relatively short postharvest life, which reduces consumer acceptance. This study aimed to evaluate the effects of exogenous melatonin application on the enzymatic activity and postharvest quality of strawberry fruits that are stored at 4 ± 0.5 °C. A total of 288 fruits with four replicates for each of the three treatments (control, 200 μM melatonin, and 500 μM melatonin) were used. Several quality metrics were regularly assessed at 3-day intervals during the 18-day storage trials. The results suggested that the exogenous melatonin application significantly increased the activity of antioxidant enzymes at the physiological level, including catalase, ascorbate peroxidase, superoxide dismutase, and peroxidase which led to reductions in weight loss, the decay incidence, and the malondialdehyde level. The use of melatonin successfully delayed changes in the soluble solids concentration, ascorbic acid, titratable acidity, and fruit firmness. The results indicated that applying 500 μM melatonin to strawberries would be a useful strategy for increasing their shelf life.

Effect of L-glutathione treatment on biochemical properties, antioxidant capacity and antioxidant enzymes activity in strawberry fruits during storage

The potential of L-glutathione (GSH) (0, 4, 16, 32 and 64 mM) to improve the post-harvest quality and antioxidant capacity of strawberries was investigated during storage (0, 5, 10, and 15 days) in this study. Results showed that weight loss in fruits treated with 64 mM GSH was significantly lower than the control. GSH treatments resulted in higher levels of total phenol content and antioxidant capacity in treated fruits of strawberry. Based on the results, GSH 64 mM significantly increased the levels of total flavonoid, anthocyanin, ascorbic acid, total soluble protein, antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (POD), ascorbate peroxidase (APX) and Phenylalanine ammonia-lyase (PAL). In addition, GSH 64 mM decreased Malondialdehyde (MDA) levels and prevented cell membrane lipid peroxidation. In conclusion, the results of the present study showed that the use of GSH 64 mM may be a promising strategy to improve the marketability, quality and antioxidant capacity of strawberry fruits during storage.

Abstract P224: RbFox2 is a Rho-related BTB Domain Containing 1 (RhoBTB1)-Cullin 3 (CUL3) Pathway Target that Regulates the Actin Cytoskeleton

Blood pressure (BP) is controlled by an array of cellular pathways. Our prior research revealed that endothelial nitric oxide (NO)-dependent vessel tone and BP are regulated through the RhoBTB1-CUL3 mediated proteasomal degradation of Phosphodiesterase 5 (PDE5). RhoBTB1 is an adaptor protein which delivers protein substrates to the CUL3 E3 ubiquitin ligase for proteasomal degradation. However, the range of protein targets of RhoBTB1 remains unknown. We employed the ascorbate peroxidase (APEX2) proximity labelling system coupled with mass spectroscopy to identify RhoBTB1 targets in A7r5 smooth muscle cells. This analysis identified nearly 75 proteins which putatively bind to the C terminal half of RhoBTB1 (known as B1B2C), the region we previously identified was essential for adaptor function. One of these proteins was RNA binding motif protein 9, known as RBM9 and RbFox2, a key regulator of splicing events. Subsequent co-immunoprecipitation (Co-IP) assays validated the interaction of RbFox2 with RhoBTB1 and its B1B2C domains. Expression of Rbfox2 was increased in response to treatment of A7r5 cells with either MG132, an inhibitor of the proteasome, and MLN4924, an inhibitor of the CUL family. Similarly, RbFox2 expression was increased in CRISPR-Cas9 generated CUL3-deficient HEK293 cells, in aorta isolated from SMC-specific CUL3-deficient mice, and in A7r5 cells expressing an siRNA targeting RhoBTB1. Ang-II treatment of mice, which raised blood pressure by 40 mmHg, also increased RbFox2 expression, presumably through down regulation of RhoBTB1. Targeting RbFox2 by siRNA in A7r5 cells resulted in a decrease in actin fiber formation detected by phalloidin staining. In summary, our findings suggest that RbFox2 regulation may occur through the RhoBTB1-CUL3 proteasomal pathway and may potentially play a mechanistic role in actin cytoskeleton organization and thus arterial stiffness associated with hypertension.

Abstract P197: Identification and Characterization of Rho-related BTB Domain Containing 1 (RhoBTB1)-Cullin 3 (CUL3) Proteins in Placenta

Preeclampsia is life threatening condition affecting about 10% of all pregnancies. A potential mechanism is via malfunctioning syncytiotrophoblasts in the placenta. RhoBTB1 is an adapter protein for the CUL3 E3 ubiquitin ligase which delivers protein substrates for proteasomal degradation. An analysis of gene expression databases revealed that the highest level of RhoBTB1 expression is in the placenta. RNAscope in situ hybridization data reveals that RhoBTB1 expression is specifically localized to syncytiotrophoblasts. In blood vessels, RhoBTB1 controls the state of nitric oxide mediated vasodilation because it acts as a substrate adaptor for Phosphodiesterase 5. Thus, we wanted to identify potential protein targets of RhoBTB1 in the placenta to assess if RhoBTB1 plays a role in placental function. To simplify the first identification of RhoBTB1 binding proteins, we employed HTR-8 /SVneo (HTR-8) cells as a model of placental trophoblast cells. We biotinylated the HTR-8 proteome utilizing ascorbate peroxidase (APEX2) proximity labelling system followed by mass spectrometry to identify RhoBTB1 targets. We employed a fusion protein consisting of the C-terminal half of RhoBTB1 (B1B2C), the region required for the binding of other protein substrates, and a control lacking the most C-terminal region (B1B2). We next chose proteins with binding to B1B2C > B1B2 of 2-fold or greater that were expressed in the placenta based on the Human Protein Atlas. Rho GTPase Activating Protein 29 (ARHGAP29), which controls the regulation of small GTP binding proteins, and S-phase Kinase associated Protein 2 (SKP2), a regulator of cell cycle progression was studied further. SKP2 is interesting because it exhibits a tissue specific tropism for placental expression with its highest expression in extravillous trophoblasts, cytotrophoblasts, and syncytiotrophoblasts. Expression of ARHGAP29 and SKP2 in HTR-8 cells were markedly upregulated by MLN4924 suggesting they are regulated by the CUL pathway. They were also modestly upregulated after partial inhibition of RhoBTB1 by siRNA suggesting they may be RhoBTB1-CUL3 targets. Studies are ongoing to validate the physical interaction of ARHGAP29 and SKP2 with RhoBTB1 by co-immunoprecipitation. We are also using RNAscope to assess the co-expression of RhoBTB1, ARHGAP29 and SKP2 in the human placenta from normal and preeclamptic pregnancies.

Brassinosteroids enhance the tolerance, production, and fruit quality of covered table grape vines

ABSTRACT Plastic covering (PC) is used to speed up the ripening and harvesting of grapes while also shielding grapevines from unfavourable climatic conditions. This study aimed to determine how PC induced abiotic stress on covered vines and assess the role of brassinosteroids (Brs) in alleviating these impacts. The results showed that PC caused a substantial rise in soluble sugar, MDA, proline, total phenol, and antioxidant enzymes (catalase and ascorbate peroxidase) and decreased insoluble sugars and carbohydrates in ‘Superior' seedless grape leaves. Applying Brs at concentrations of 0, 1, 2, and 3 mg/l twice during the berry development stages (pea and veraison) enhanced the plants’ ability to withstand PC-induced stress. The concentration of 3 mg/l Brs elevated some metabolic activities, including insoluble sugar, total carbohydrates, proline, and total phenol. Additionally, it increased the antioxidant enzyme activity. Meanwhile, 2 mg/l appeared to be the most effective concentration in achieving the highest cluster and berry weight, enhanced total soluble solids (TSS) and firmness, and reduced weight loss over shelf life. In conclusion, applying Brs could be a promising strategy to alleviate the adverse effect of abiotic stress on table grapes.

Effector CLas0185 targets methionine sulphoxide reductase B1 of Citrus sinensis to promote multiplication of 'Candidatus Liberibacter asiaticus' via enhancing enzymatic activity of ascorbate peroxidase 1.

Citrus huanglongbing (HLB) has been causing enormous damage to the global citrus industry. As the main causal agent, 'Candidatus Liberibacter asiaticus' (CLas) delivers a set of effectors to modulate host responses, while the modes of action adopted remain largely unclear. Here, we demonstrated that CLIBASIA_00185 (CLas0185) could attenuate reactive oxygen species (ROS)-mediated cell death in Nicotiana benthamiana. Transgenic expression of CLas0185 in Citrus sinensis 'Wanjincheng' enhanced plant susceptibility to CLas. We found that methionine sulphoxide reductase B1 (CsMsrB1) was targeted by the effector, and its abundance was elevated in CLas0185-transgenic citrus plants. Their interaction promoted CLas proliferation. We then determined that CsMsrB1 sustained redox state and enzymatic activity of ascorbate peroxidase 1 (CsAPX1) under oxidative stress. The latter reduced H2O2 accumulation and was associated with host susceptibility to CLas infection. Consistently, citrus plants expressing CLas0185 and CsMsrB1 conferred enhanced APX activity and decreased H2O2 content. Taken together, these findings revealed how CLas0185 benefits CLas colonization by targeting CsMsrB1, which facilitated the antioxidant activity and depressed ROS during pathogen infection.

Ameliorative effects of humic acid and L-tryptophan onenzyme activity, mineral content, biochemical properties, and plant growth of spinach cultivated in saline conditions.

Salinity poses a significant abiotic stress that limits plant productivity, thereby posing a serious threat to agricultural sustainability and worldwide food security. Techniques that can overcome this problem are needed. Recent focus has been placed on employing organic substances like humic acid (HA) and amino acids, including L-tryptophan (L-TRP), to mitigate the negative effects of salt stress on cultivated plants. Accordingly, in this research, the impact of foliar applications of HA and L-TRP, both separately and combined, on the growth parameters and biochemical properties of spinach subjected to salt stress was investigated. In the present study, eight treatments (1. control, 2. salt (NaCl), 3. HA, 4. L-TRP, 5. HA + NaCl, 6. L-TRP + NaCl, 7. HA + L-TRP, and 8. HA + L-TRP + NaCl) were investigated. The study showed that salt stress markedly reduced several growth properties in spinach, including plant height, number of leaves, leaf dimensions, and both fresh and dry weight. Additionally, it significantly lowered contents of chlorophyll (a, b, and total), carotenoid, polyphenol, lutein, anthocyanin, polyphenol oxidase, glycine betaine, relative water content, and the antioxidant enzyme activities (ascorbate peroxidase, catalase, peroxidase, and superoxide dismutase). On the other hand, significant increases were observed in sodium, chlorine, potassium, sulfur, zinc, nickel, proline, malondialdehyde, and hydrogen peroxide levels of spinach with salinity. Individual and combined applications of HA and L-TRP positively influenced plant growth, relative water content, activities of antioxidant enzyme, chlorophyll, and mineral contents of spinach under both normal and saline conditions. In conclusion, the combined use of HA and L-TRP under salt stress conditions is promising in mitigating the negative impacts of salinity and can be suggested as an effective alternative approach for cultivating spinach in saline environments.

Involvement of BcNAC083 in 1-MCP-induced delayed yellowing of pak choi (Brassica rapa subsp. Chinensis) through the regulation of reactive oxygen species metabolism and inhibition of major chlorophyll catabolic genes

Leaf yellowing is a typical senescence feature in postharvest pak choi. Plant-specific NAC transcription factors (TFs) are crucial regulators of plant senescence. In this study, a senescence-related NAC TF, BcNAC083, was investigated to identify its transcriptional regulation effects on the yellowing of pak choi by treatment with 1-methylcyclopropene (1-MCP). Applying 5.0 µL L–1 1-MCP alleviated yellowing and maintained a low respiration rate, high chlorophyll content, and relatively complete chloroplast structure in pak choi during storage. However, 10 μL L–1 ethylene accelerated yellowing, as demonstrated by the higher respiration rate, lower chloroplast structural integrity and chlorophyll content. In contrast to ethylene treatment, 1-MCP suppressed the activity of the reactive oxygen species (ROS) metabolism-related enzymes superoxide dismutase (SOD), catalase (CAT), ascorbic peroxidase (APX), and lipoxygenase (LOX), and correspondingly reduced superoxide anion (O2·–), hydrogen peroxide (H2O2), and malondialdehyde (MDA) accumulation. 1-MCP treatment also suppressed the transcript levels of ROS metabolic genes, including BcRBOHC, BcRBOHD, BcSOD, BcCAT, BcAPX, and BcLOX, and inhibited the activity of the chlorophyll catabolic enzymes chlorophyllase (CLH), Mg-de-chelatase, and pheophytin pheophorbide hydrolase (PPH) and transcript levels of associated genes, including BcCLH1/2, BcPPH1/2, BcPAO, BcNYC1, BcSGR1/2, BcHCAR, BcRCCR, and BcCAO. The expression of BcNAC083 was probably induced by ROS and was downregulated by 1-MCP and upregulated by ethylene. Molecular biology experiments determined that BcNAC083 bound directly to and activated the promoters of the chlorophyll metabolism-related genes BcCLH1, BcPPH1, BcNYC1, and BcHCAR. Importantly, transient overexpression of BcNAC083 stimulated the endogenous genes (NbCLH1, NbPPH1, NbNYC1, and NbHCAR) expression in tobacco leaves, resulting in rapid chlorophyll breakdown and leaf degreening. Treatment with 1-MCP may alleviated the yellowing of pak choi by inhibiting ROS accumulation and the transcriptional regulation of BcNAC083, which had positive regulatory effects on major chlorophyll metabolic genes.

Physiological and biochemical responses of the achachairu tree (Garcinia humilis) to prolonged flooding

Flooding and waterlogging create hypoxic or anoxic soil conditions that negatively affect the physiology of wild and cultivated tropical fruit trees. The achachairu (Garcinia humilis) is a slow-growing tropical fruit tree endemic to the Bolivian Amazon region. Like many tropical trees, G. humilis is increasingly affected by flooding events that may threaten its natural and cultivated areas, but its physiological and biochemical responses to prolonged flooding have not been reported. This study assessed the physiological, biochemical, and morphological responses of G. humilis to prolonged flooding of different durations for up to 30 d Physiological variables measured included leaf gas exchange [net CO2 assimilation (A), stomatal conductance of H2O (gs), and intercellular CO2 concentration (Ci)], leaf chlorophyll index (LCI), and the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm). Antioxidant responses, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione (GSH), glutathione reductase (GTR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDAR), ascorbic acid (AsA), and glutathione (GSH); reactive oxygen species (ROS); and lipid peroxidation indicated by malondialdehyde (MDA) were also measured. Results indicate that G. humilis is very tolerant of flooding periods of at least 30 d, which causes approximately a 50 % reduction in net A but no measurable negative impact on other physiological variables, including LCI and Fv/Fm. Flooding caused an increase in ROS and malonaldehyde (MDA), which were countered by a robust antioxidant response that possibly contributed to improved flooding tolerance. Plants continued to grow during the flooding period, and A recovered to nearly pre-flooding levels 90 d after plants were unflooded.

Integrative approach to mitigate chromium toxicity in soil and enhance antioxidant activities in rice (Oryza sativa L.) using magnesium-iron nanocomposite and Staphylococcus aureus strains.

Pollutantsin soil, particularly chromium (Cr), posehigh environmental and health risks due to their persistence, bioavailability, and potential for causing toxicity. Cr impairment in plants act as a deleterious environmental pollutant that enters the food chain and eventually disturbs human health. Current study demonstrated the potential of integrative foliar application of magnesium-iron (Mg +Fe) nanocomposite with Staphylococcus aureus strains to alleviate Cr toxicity in rice (Oryza sativa) crops by improving yield and defense system. Growth and yield traits such as shoot length (15%), root length (17%), shoot fresh weight (14%), shoot dry weight (9%), root fresh weight (23%), root dry weight (7%), number of tillers (33%), number of grains (10%) and spike length (13%) improved by combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1), compared to when applied alone. Mutual Mg + Fe and S. aureus strains application augmented the SPAD value (9%), total chlorophyll (11%), a (12%), b (17%), and carotenoids (32%), with Cr (110mgkg-1), compared to alone. Malondialdehyde (13%), hydrogen peroxide (H2O2) (11%), and electrolyte leakage (7%) were significantly regulated in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) contrasted to alone. Peroxidase (20%), superoxide dismutase (17%), ascorbate peroxidase (18%), and catalase (20%) were increased in shoots with combined Mg + Fe and S. aureus strains application with Cr (110mgkg-1) in comparison to alone. The combined application of Mg + Fe (20mgL-1) nanocomposite and S. aureus strains with Cr (110mgkg-1) enhanced the macro-micronutrients in shoots compared to alone. Cr accumulation in roots (21%), shoots (25%), and grains (47%) were significantly reduced under Cr (110mgkg-1) with combined Mg + Fe and S. aureus strains application, compared to alone. Subsequently, applying combined Mg + Fe and S. aureus strains is a sustainable solution to boost crop production under Cr toxicity.

Screening and Physiological Responses of Maize Inbred Lines to Drought Stress in South China

The frequent occurrence of localized and seasonal droughts has caused severe economic losses in maize production in South China. To promote sustainable maize production, selecting and breeding drought-tolerant varieties is vital for addressing water scarcity. Drought stress affects all aspects of crop morphological performance. In this study, the morphological performance of 285 maize inbred lines under drought stress was investigated using D-value analysis, correlation analysis, principal component analysis, cluster analysis and stepwise regression analysis. All indicators were significantly different in the regular treatment compared to the drought treatment. Specifically, survival rate, root fresh weight, root dry weight, plant dry weight, root/crown ratio, and plant fresh weight were used as indicators for drought-tolerance evaluation. Furthermore, the drought-tolerant inbred line CML323 and the drought-sensitive inbred line CB2-49-1 were screened by comprehensively evaluating D values. The drought-tolerant inbred line CML323 exhibits higher leaf relative water content, chlorophyll content, proline content, and ascorbate peroxidase and peroxidase activity while having lower malondialdehyde content, consequently demonstrating excellent drought tolerance. This study provides valuable insights into drought-tolerance indicators and reference materials for breeding maize varieties.

Mitigating High-Temperature Stress in Peppers: The Role of Exogenous NO in Antioxidant Enzyme Activities and Nitrogen Metabolism

This study investigated the effects of exogenous nitric oxide (NO) on growth, antioxidant enzymes, and key nitrogen metabolism enzymes in pepper seedlings under high-temperature stress. In addition, targeted metabolomics was used to study the differential accumulation of amino acid metabolites, thereby providing theoretical support for the use of exogenous substances to mitigate high-temperature stress damage in plants. The results showed that high-temperature stress increased soluble sugar, soluble protein, amino acids, proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, electrolyte leakage, and superoxide anion (O2·-) production rate while altering the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX)] and key nitrogen metabolism enzymes [nitrate reductase (NR), glutamine synthetase (GS), glutamate dehydrogenase (GDH), and nitric oxide synthase (NOS)]. c-PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, an NO scavenger) exacerbates oxidative stress and further reduces NO content and enzyme activities. However, exogenous SNP (sodium nitroprusside, an NO donor) effectively alleviated these adverse effects by enhancing antioxidant defense mechanisms, increasing NO content, and normalizing amino acid metabolite levels (kynurenine, N-acetyl-L-tyrosine, L-methionine, urea, and creatine), thereby maintaining normal plant growth. These findings suggest that SNP can enhance stress tolerance in pepper seedlings by improving osmotic regulation, antioxidant capacity, and nitrogen metabolism, effectively mitigating the damage caused by high-temperature stress.

Biomonitoring of Heavy Metal Toxicity in Freshwater Canals in Egypt Using Creeping Water Bugs (Ilyocoris cimicoides): Oxidative Stress, Histopathological, and Ultrastructural Investigations.

The abundance of metal pollutants in freshwater habitats poses serious threats to the survival and biodiversity of aquatic organisms and human beings. This study intends for the first time to assess the pernicious influences of heavy metals in Al Marioteya canal freshwater in Egypt, compared to Al Mansoureya canal as a reference site utilizing the creeping water bug (Ilyocoris cimicoides) as an ecotoxicological model. The elemental analysis of the water showed a significantly higher incidence of heavy metals, including cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb), in addition to the calcium (Ca) element than the World Health Organization's (WHO) permitted levels. The Ca element was measured in the water samples to determine whether exposure to heavy metals-induced oxidative stress engendered Ca deregulation in the midgut tissues of the creeping water bug. Remarkably, increased levels of these heavy metals were linked to an increase in chemical oxygen demand (COD) at the polluted site. Notably, the accumulation of these heavy metals in the midgut tissues resulted in a substantial reduction in antioxidant parameters, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and ascorbate peroxidase (APOX), along with a marked rise in malondialdehyde (MDA), cytochrome P450, and protein carbonyl levels. These results clearly indicate a noticeable disturbance in the antioxidant defense system due to uncontrollable reactive oxygen species (ROS). Notably, the results demonstrated that oxidative stress caused disturbances in Ca levels in the midgut tissue of I. cimicoides from polluted sites. Furthermore, the comet and flow cytometry analyses showed considerable proliferations of comet cells and apoptotic cells in midgut tissues, respectively, exhibiting prominent correlations, with pathophysiological deregulation. Interestingly, histopathological and ultrastructural examinations exposed noticeable anomalies in the midgut, Malpighian tubules, and ovarioles of I. cimicoides, emphasizing our findings. Overall, our findings emphasize the potential use of I. cimicoides as a bioindicator of heavy metal pollution in freshwater to improve sustainable water management in Egypt.

Glycine betaine enhances chilling tolerance in peach fruit by modulating PpbHLH130-mediated antioxidant metabolism

Peaches are vulnerable to chilling injury (CI) after long-term refrigeration. Glycine betaine (GB) treatment was found to substantially mitigate CI in peach fruit, but its molecular mechanism is still unclear. In this study, 288 uniformly sized fruit for three repetitions were immersed in 10 mmol L−1 GB for 10 min and then stored at 5 ± 0.5 °C for 49 d. GB-treated peaches retained lower levels of internal browning index, relative conductivity and malondialdehyde content compared to control during cold storage. Meanwhile, GB treatment increased the gene expression and activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), accompanied by decreased reactive oxygen species (ROS) content in cold stored peaches. Moreover, PpbHLH130 transcription factor was cloned by a one-step cloning method from peaches, which was located in the nucleus with transcriptional activation ability. PpbHLH130 expression was induced by chilling stress and GB treatment. Further investigation revealed that PpbHLH130 up-regulated the expression of PpPOD and PpAPX by directly interacting with E-box elements in their promoters. Therefore, these results indicated that GB treatment activated the PpbHLH130-mediated transcriptional activation of PpPOD and PpAPX genes, improved the gene expression and activities of antioxidant-related enzymes and suppressed the accumulation of ROS, contributing to the maintenance of cell membrane integrity and the improvement of chilling tolerance in refrigerated peach fruit.

Efficacy of Fe-Mg-bimetallic biochar in stabilization of multiple heavy metals-contaminated soil and attenuation of toxicity in spinach (Spinacia oleracea L.)

Globally, soil contamination with heavy metals (HMs) pose serious threats to soil health, crop productivity, and human health. The present investigation involved synthesis and analysis of biochar with bimetallic combination of iron and magnesium (Fe-Mg-BC). Our study evaluated how Fe-Mg-BC affects the absorption of cadmium (Cd), lead (Pb), and copper (Cu) in spinach (Spinacia oleracea L.) and remediation of soil contaminated with multiple HMs. Results demonstrated the successful loading of iron (Fe) and magnesium (Mg) onto pristine biochar (BC) derived from peanut shells. The addition of Fe-Mg-BC (3%) notably increased spinach biomass, enhancing photosynthesis, transpiration, stomatal conductance, and intercellular CO2 levels by 22%, 21%, 103%, and 15.3%, respectively. Compared to control, Fe-Mg-BC (3%) suppressed metal-induced oxidative stress by boosting levels of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) in roots by 40.9%, 57%, 54.8 %, and in shoots by 55.5%, 65.5%, and 37.4% in shoots, respectively. The Fe-Mg-BC effectively reduced the uptake of Cd, Pb, and Cu in spinach tissues by transforming their bioavailable fractions to non-bioavailable forms. The Fe-Mg-BC (3%) significantly reduced the mobility of Cd, Pb and Cu in soil and limited the concentration of Cd, Pb, and Cu in plant roots by 34.1%, 79.2%, 47%, and shoots by 56.3%, 43.3%, and 54.1%, respectively, compared to control. These findings underscore the potential of Fe-Mg-BC as a promising amendment for reclaiming soils contaminated with variety of HMs, thereby making a significant contribution to the promotion of safer food production.