Nickel Stress Research Articles

Individual and combinatorial application of nanosilica and carbon nanoparticles alleviate nickel stress in barley (Hordeum vulgare L.): Impacts on gene expression, AsA − GSH cycle, cellular fractionation, and proline metabolism

Nanotechnology is grabbing great attention all over the world because of its stimulating use in numerous fields, and the nanosilica (nSi) and carbon nanoparticles (CNPs) application has been examined in various studies. Conversely, the nSi and CNPs combinatorial use is a new method and researched in limited literature. For this purpose, a pot experiment was conducted to examine various growth and biochemical parameters in barley (Hordeum vulgare L.) under the toxic concentration of nickel (Ni) i.e., 200 mg kg−1 which were primed with combined application of two NPs of nSi at 3 mM and CNPs i.e., 200 μM respectively. The results showed that the Ni toxicity in the soil showed a significantly (P < 0.05) declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in H. vulgare. However, Ni toxicity significantly (P < 0.05) increased oxidative stress biomarkers, enzymatic and nonenzymatic antioxidants including their gene expression in H. vulgare. Although, the application of nSi and CNPs showed a significant (P < 0.05) increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, and Ni uptake. In addition, individual or combined application of nSi and CNPs enhanced the cellular fractionation and decreases the proline metabolism and AsA−GSH cycle in H. vulgare. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Transcriptome Analysis of the Effect of Nickel on Lipid Metabolism in Mouse Kidney.

Although the human body needs nickel as a trace element, too much nickel exposure can be hazardous. The effects of nickel on cells include inducing oxidative stress, interfering with DNA damage repair, and altering epigenetic modifications. Glucose metabolism and lipid metabolism are closely related to oxidative stress; however, their role in nickel-induced damage needs further study. In Institute of Cancer Research (ICR) mice, our findings indicated that nickel stress increased the levels of blood lipid indicators (triglycerides, high-density lipoprotein, and cholesterol) by about 50%, blood glucose by more than two-fold, and glycated serum protein by nearly 20%. At the same time, nickel stress increased oxidative stress (malondialdehyde) and inflammation (Interleukin 6) by about 30% in the kidney. Based on next-generation sequencing technology, we detected and analyzed differentially expressed genes in the kidney caused by nickel stress. Bioinformatics analysis and experimental verification showed that nickel inhibited the expression of genes related to lipid metabolism and the AMPK and PPAR signaling pathways. The finding that nickel induces kidney injury and inhibits key genes involved in lipid metabolism and the AMPK and PPAR signaling pathways provides a theoretical basis for a deeper understanding of the mechanism of nickel-induced kidney injury.

Exploring the morpho-physiological responses of maize to nickel stress modulated by salicylic acid

Exploring the morpho-physiological responses of maize to nickel stress modulated by salicylic acid

Mechanism of Mitochondrial Kinetic Imbalance and Nrf2 Signaling Pathway-Mediated Oxidative Stress in Nickel and/or Chromium-Induced Kidney Injury in Mice.

Nickel and chromium are both common heavy metals that pose serious environmental and health hazards. However, the exact mechanism by which nickel and/or chromium cause renal injury is unclear. Therefore, we explored the molecular mechanisms of renal injury caused by nickel and/or chromium poisoning from the perspective of mitochondrial dynamics and the Nrf2 antioxidant pathway. In this study, eighty 6-week-old C57BL/6J mice were randomly divided into four groups: control (Con, untreated), nickel (Ni, 110 mg/L Ni2+), chromium (Cr, 50 mg/L Cr6+), and combined nickel-chromium (Ni + Cr, 110 mg/L Ni2+, 50 mg/L Cr6+). The results showed that chronic nickel and/or chromium exposure inhibited body weight gain and impaired kidney function and structure in mice. Chronic nickel and/or chromium exposure led to the disruption of mitochondrial dynamics and thus induced oxidative stress. On the other hand, the Nrf2 antioxidant pathway may play an important regulatory role in mitigating oxidative stress-induced oxidative damage in kidney. The present study partially elucidated the molecular mechanism of renal injury induced by nickel and/or chromium exposure in mice and the regulatory role of the Nrf2 pathway in inducing oxidative injury from the perspective of mitochondrial dynamics. This provides a theoretical basis for the development of prevention and control strategies, and environmental protection measures.

Molecular dynamics simulation of crack growth in nanocrystalline nickel considering the effect of accumulated plastic deformation

Molecular dynamics simulations are conducted to investigate atomic stress and plastic strain distribution in pre-cracked crystalline nickel, along with microstructure evolution. The plastic strain calculation method is improved by refining neighboring atom selection. A new parameter for measuring plastic strain concentration allows for comparison across different crystallographic directions. The effects of temperature, strain rate, crystallographic direction, loading mode, grain boundary and grain size are evaluated. At elevated temperature, crack tip blunting becomes obvious, and crack propagation decelerates. The crack propagates through void nucleation, growth, and eventual linkage with the original crack. Higher temperature increases the plasticity limit of void nucleation. Strain rates show a positive correlation with plasticity limit but a negative correlation with crack growth rate and final length. Crystallographic direction influences crack propagation, with crystal 100 exhibiting significant crack propagation, while 110 and 111 demonstrating marked resistances to crack propagation. Crystal 100 has the highest plastic deformation concentration near the crack tip. Loading mode affects plastic deformation accumulation. In-plane shear results in less plastic deformation and less obvious crack propagation. In bi-crystals, the relative rotation angle between grains significantly influences crack propagation. X-rotation of the right grain most significantly impedes crack propagation, while y- and z-rotation tend to cause the crack to cross the grain boundary. In polycrystals, plastic deformation accumulation at grain boundaries is significant, with the crack tending to propagate along grain boundaries. Plastic strain and concentration parameter peaks are lower in grain boundaries than in single crystals, indicating weaker stability. The results demonstrate that the failure process of crystalline nickel is intricately linked to the stress and plastic strain distribution around the crack tip. The plastic strain and concentration parameter are more accurate predictors of crack propagation than atomic stress.

The effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea mays L.) exposed to nickel stress.

The issue of heavy metal pollution such as nickel poses a significant environmental concern, exerting detrimental effects on the growth and viability of plant life. Plants have various mechanisms to effectively manage heavy metal stress, including the ability to modify their amino acid type and content. This adaptive response allows plants to mitigate the detrimental effects caused by excessive heavy metal accumulation. The aim of this study was to investigate the effect of biofertilizers on nickel accumulation, nitrogen metabolism and amino acid profile of corn (Zea maysL.) cv. 'PL438' exposed to Ni stress. After disinfecting and soaking in water for 24 h, corn seeds were primed with bacterial biofertilizers (T2: NPK + FZ), fungal biofertilizers (T3: Arbuscular mycorrhizal fungi (AMF) + Trichoderma (T)), or a combination of them (T4: NPK + FZ + AMF + T) and were cultured by the hydroponic method in completely controlled conditions. Then, they were simultaneously exposed to nickel chloride at various rates (0, 75, or 150 µM) at the three-leaf stage. They were harvested two weeks later and were subjected to the measurement of Ni content, nitrate and nitrite content, nitrate reductase activity, and amino acid profile by high-performance liquid chromatography. The results showed that the application of Ni at higher rates increased Ni, nitrate, and nitrite contents and nitrate reductase activity. The study of Ni accumulation and TF revealed that Ni accumulated in the roots to a greater extent than in the shoots and TF was < 1 in all treatments. The shoot amino acid profile showed that the treatment of Ni+2 increased som amino acids such as aspartic acid, asparagine, serine, histidine, and glycine versus the control, whereas T4Ni+2 increased aspartic acid, glutamic acid, threonine and arginine. The change in amino acids in Ni-treated plants may play a key role in their adaptation to Ni stress. The findings indicate that biofertilizers played a crucial role in mitigating the negative impacts of Ni on corn plants through alterations in amino acid composition and decreased absorption and translocation of Ni.

Biochemical Responses of Date Palm Phoenix dactylifera L. to Combined Stress of Salinity and Nickel

This study examined the effects of nickel (Ni) at 0, 25, and 50 mg.L-1 concentrations, applied alone or in combination with salinity (represented by NaCl at 0, 100, and 200 mM concentrations), on the biochemical traits of date palm. Hydrogen peroxide (H2O2), malondialdehyde (MDA), membrane stability index (MSI), peroxidase (POD) activity, superoxide dismutase (SOD), and proline content were among the parameters evaluated. The results revealed significant effects of nickel and salinity on the studied biochemical markers. Nickel at 50 mg.L-1 significantly increased H2O2 (0.87 µmol. L-1) and MDA (2.46 nmol.g-1) levels, while decreasing MSI (75.85%). Moreover, it enhanced POD (25.09 U.min-1.g-1) and SOD (3.78 U. min-1.g-1) activity, as well as proline content (4.35 µmol.g-1). Salinity at 200 mM significantly increased H2O2 (0.90 µmol L-1) and MDA (2.54 nmol.g-1) levels, decreased MSI (77.69%), and increased POD (27.61 U. min-1.g-1) and SOD (3.77 U.min-1.g-1) activity, along with increased proline content (4.54 µmol.g-1). Additionally, the combined application of nickel and salinity, particularly at higher concentrations, resulted in significantly increased biochemical responses compared to individual treatments. The findings highlight the interactive effects of nickel and salinity on the oxidative and antioxidant mechanisms in date palm plants. This study contributes to our understanding of plant responses to abiotic stressors and provides insights for optimizing date palm cultivation under challenging environmental conditions.

Transcriptome and metabolome analysis reveal key genes and metabolic pathway responses in Leersia hexandra Swartz under Cr and Ni co-stress

Phytoremediation, an eco-friendly approach for mitigating heavy metal contamination, is reliant on hyperaccumulators. This study focused on Leersia hexandra Swart, a known chromium (Cr) hyperaccumulator with demonstrated tolerance to multiple heavy metals. Our objective was to investigate its response to simultaneous Cr and nickel (Ni) stress over 12 days. Results from physiological experiments demonstrated a significant increase in the activities of antioxidant enzymes (APX, SOD, CAT) and glutathione (GSH) content under Cr and Ni stress, indicating enhanced antioxidant mechanisms. Transcriptome analysis revealed that stress resulted in the differential expression of 27 genes associated with antioxidant activity and metal binding, including APX, SOD, CAT, GSH, metallothionein (MT), and nicotinamide (NA). Among them, twenty differentially expressed genes (DEGs) related to GSH metabolic cycle were identified. Notably, GSTU6, GND1, and PGD were the top three related genes, showing upregulation with fold changes of 4.57, 6.07, and 3.76, respectively, indicating their crucial role in metal tolerance. The expression of selected DEGs was validated by quantitative real-time PCR, confirming the reliability of RNA-Seq data. Metabolomic analysis revealed changes in 1121 metabolites, with amino acids, flavonoids, and carbohydrates being the most affected. Furthermore, glucosinolate biosynthesis and amino acid biosynthesis pathways were represented in the KEGG pathway of differentially expressed metabolites (DEMs). This study provides insights into the tolerance mechanisms of L. hexandra under the co-stress of Cr and Ni, offering a new perspective for enhancing its remediation performance.

Metal-tolerant morganella morganii isolates can potentially mediate nickel stress tolerance in Arabidopsis by upregulating antioxidative enzyme activities

ABSTRACT Plant growth-promoting rhizobacteria (PGPRs) have been utilized to immobilize heavy metals, limiting their translocation in metal contaminated settings. However, studies on the mechanisms and interactions that elucidate how PGPRs mediate Nickel (Ni) tolerance in plants are rare. Thus, in this study we investigated how two pre-characterized heavy metal tolerant isolates of Morganella morganii (ABT9 and ABT3) improve Ni stress tolerance in Arabidopsis while enhancing its growth and yield. Arabidopsis seedlings were grown for five weeks in control/Ni contaminated (control, 1.5 mM and 2.5 mM) potted soil, in the presence or absence of PGPRs. Plant growth characteristics, quantum yield, and antioxidative enzymatic activities were analyzed to assess the influence of PGPRs on plant physiology. Oxidative stress tolerance was quantified by measuring MDA accumulation in Arabidopsis plants. As expected, Ni stress substantially reduced plant growth (shoot and root fresh weight by 53.25% and 58.77%, dry weight by 49.80% and 57.41% and length by 47.16% and 64.63% over control), chlorophyll content and quantum yield (by 40.21% and 54.37% over control). It also increased MDA content by 84.28% at higher (2.5 mM) Ni concentrations. In contrast, inoculation with M. morganii led to significant improvements in leaf chlorophyll, quantum yield, and Arabidopsis biomass production. The mitigation of adverse effects of Ni stress on biomass observed in M. morganii-inoculated plants was attributed to the enhancement of antioxidative enzyme activities compared to Ni-treated plants. This upregulation of the antioxidative defense mechanism mitigated Ni-induced oxidative stress, leading to improved performance of the photosynthetic machinery, which, in turn, enhanced chlorophyll content and quantum yield. Understanding the underlying mechanisms of these tolerance-inducing processes will help to complete the picture of PGPRs-mediated defense signaling. Thus, it suggests that M. morganii PGPRs candidate can potentially be utilized for plant growth promotion by reducing oxidative stress via upregulating antioxidant defense systems in Ni-contaminated soils and reducing Ni metal uptake.

Physiological and biochemical response of finger millet plants exposed to arsenic and nickel stress

Heavy metal stress is one of the major abiotic stresses that affects growth, development and yield in cereals. This investigation was conducted to examine the toxic effects of arsenic (As), nickel (Ni) and arsenic + nickel (As + Ni) on finger millet seedlings. The experiment involves exposing fourteen-day-old finger millet plants to various concentrations of As (10, 25, 50 and 100 µM), Ni (100, 250, 500 and 1000 µM) and As + Ni (10 + 100, 25 + 250, 50 + 500 and 100 + 1000 µM). The presence of heavy metals (HMs) led to oxidative stress and decreased root and shoot length, biomass, total chlorophyll, and leaf relative water content (LRWC). In addition, the levels of electrolyte leakage (EL), proline, H2O2, and MDA content increased significantly at higher concentrations of HMs (As >50 µM, Ni >500 µM and As + Ni >50 + 500 µM). An increased accumulation of As and Ni was found in roots compared to shoots. This is the first report to identify the physiological and biochemical responses of finger millet plants exposed to Arsenic and Arsenic + Nickel combined stress.

Physiological and biochemical responses of Leersia hexandra Swartz to nickel stress: Insights into antioxidant defense mechanisms and metal detoxification strategies

Phytoremediation is widely considered as a cost-effective method for managing heavy metal soil pollution. Leersia hexandra Swartz shows a promising potential for the remediation of heavy metals pollution, including chromium (Cr), copper (Cu), and nickel (Ni). It is vital to understand the physiological and biochemical responses of L. hexandra to Ni stress to elucidate the mechanisms underlying Ni tolerance and accumulation. Here, we examined the metabolic and transcriptomic responses of L. hexandra exposed to 40 mg/L Ni for 24 h and 14 d. After 24-h Ni stress, gene expression of glutathione metabolic cycle (GSTF1, GSTU1 and MDAR4) and superoxide dismutase (SODCC2) was significantly increased in plant leaves. Furthermore, after 14-d Ni stress, the ascorbate peroxidase (APX7), superoxide dismutase (SODCP and SOD1), and catalase (CAT) gene expression was significantly upregulated, but that of glutathione metabolic cycle (EMB2360, GSTU1, GSTU6, GSH2, GPX6, and MDAR2) was downregulated. After 24-h Ni stress, the differentially expressed metabolites (DEMs) were mainly flavonoids (45%) and flavones (20%). However, after 14-d Ni stress, the DEMs were mainly carbohydrates and their derivatives (34%), amino acids and derivatives (15%), and organic acids and derivatives (8%). Results suggest that L. hexandra adopt distinct time-dependent antioxidant and metal detoxification strategies likely associated with intracellular reduction–oxidation balance. Novel insights into the molecular mechanisms responsible for Ni tolerance in plants are presented.

Taurine Enervates Nickel Stress in Lagenaria siceraria by regulating Redox Balance, Methylglyoxal Detoxification, H2S Production, and Nickel Uptake

Taurine Enervates Nickel Stress in Lagenaria siceraria by regulating Redox Balance, Methylglyoxal Detoxification, H2S Production, and Nickel Uptake

Isozyme profiling of Antioxidant Enzyme in Macrotyloma uniflorum

The current climate change and pollution scenario has invariably increased the abiotic stress of salinity, heavy metals, and temperature on plants. Abiotic stress impacts the plant's defense system, impacting the crop's growth, yield, and productivity. The present investigation emphasised the antioxidant ability of Macrotyloma uniflorum under nickel stress which forms a major part of defense mechanism. It intricately evaluates the antioxidant activities of M. uniflorum with respect to different Nickel doses. The antioxidant defense system of plants includes enzymes including super oxide dismutase (SOD), catalase (CAT), peroxidase (POX), glutathione peroxidase (GPX), and dehyrdoascorbate reductase (DHAR). These enzymes act as scavengers to ameliorate the free radicals cellular metabolism produces. Therefore, the present study gives a comprehensive understanding of the antioxidant enzymatic system with special reference to the role of each enzyme in response to the abiotic stress, especially nickel. By studying the isozyme pattern of these enzymes, we can compute the antioxidant activities in a very detailed manner. Different concentrations of Ni in the range of 25 ppm to 125 ppm were taken to find the optimum concentration of Ni for its antioxidant activities. SOD1 isozyme was the most prominent one among all at 25 ppm. The intensity of GPX2 in the black variety is more prominent at 100 ppm as compared to the control. Thus, the results obtained could be easily used to evaluate the minimum concentration of Nickel for antioxidant.

The TaSep15–like-B-TaUGGT-B2–TaVSR-B pathway positively regulates nickel stress in wheat

The function and mechanism of proteins involved in the endoplasmic reticulum (ER) quality control system in plants in the response to heavy metals remain largely unknown. In this study, 15-kDa selenoprotein (Sep15) homolog gene (Sep15-like) was characterized in wheat. Its transcript, induced by nickel treatment, was abundant in the roots and leaves, and its protein localized to the ER. Constitutive TaSep15-like-B expression enhanced tolerance to nickel stress in wheat and Arabidopsis, likely via the regulation of ER stress homeostasis and ROS balance. Wheat UDP-glucose:glycoprotein glucosyltransferase (UGGT)-B2, a key enzyme in ER quality control with the reglucosylation of the glycoprotein, was identified as a partner of TaSep15-like-B. Further studies revealed that TaUGGT-B2 interacted with a wheat vacuolar sorting receptor B, TaVSR-B, which mediates the sorting of soluble proteins to vacuoles in the secretory pathway. Our findings revealed a mechanistic framework underlying the TaSep15-like-B-TaUGGT-B2-TaVSR-B module-mediated regulation of nickel response.

Ecotoxicology of Polymetallic Nodule Seabed Mining: The Effects of Cobalt and Nickel on Phytoplankton Growth and Pigment Concentration.

In order to improve the understanding of the environmental impacts of polymetallic nodule mining, ecotoxicological studies were conducted on the growth of model phytoplankton species Skeletonema costatum and Prorocentrum donghaiense using cobalt and nickel. This study evaluated various physiological and ecological indicators, such as cell proliferation, chlorophyll a, pigments, total protein, and antioxidant enzyme markers. The results show that the introduction of low amounts of cobalt or nickel increased the growth rate of phytoplankton. The phytoplankton benefited from low concentrations of cobalt and nickel stress. The increased protein levels and decreased activity of antioxidant enzymes considerably impacted physiological responses during the promotion of cell abundance. High concentrations of cobalt or nickel resulted in decreased light-absorbing pigments, increased photoprotective pigments, an inactive chlorophyll content, decreased total proteins, and maximal antioxidant enzyme activity in phytoplankton. Throughout the experiment, both the phytoplankton protein and enzyme activity declined with prolonged stress, and the cells underwent age-induced damage. Thus, seabed mining's repercussions on phytoplankton could result in both short-term growth promotion and long-term damage. These consequences depend on the impurity concentrations infiltrating the water, their duration, and the organism's physiological responses.

Nickel toxicity mitigation by supplementation of acetylcholine in wheat: Growth, photosynthetic and antioxidant activities

Influence of exogenous treatment of acetylcholine (ACh; 5 and 10 µM) was studied on the growth, photosynthesis and nitrate reductase activity in wheat under nickel (500 µM Ni) stress. Plant height, fresh and dry weight of shoot showed a decline of 36%, 23% and 40% respectively while as increased by 35%, 44% and 47% due to 10 µM ACh over control. Treatment of ACh, at both concentrations, alleviated the decline with obvious effects at higher (10 µM) concentrations. Treatment of ACh resulted in increased content of total chlorophylls, carotenoids and photosynthesis, intercellular carbon dioxide, transpiration and PSII activity, which were however significantly reduced by Ni stress. Exogenous application of ACh alleviated the Ni stress mediated decline in the activity of nitrate reductase. Wheat plants treated with Ni showed increased production of hydrogen peroxide resulting in increased lipid peroxidation and electrolyte leakage, however treatment of ACh reduced these parameters significantly reflecting in alleviation of oxidative damage. Activity of antioxidant enzymes assayed (SOD, CAT, APX, DHAR and GR) and the content of ascorbic acid and reduced glutathione increased significantly in ACh treated plants under normal and Ni stress. Activities of SOD, CAT, APX, DHAR and GR was increased by 162%, 108%, 70%, 107% and 87% respectively in Ni + 10 µM ACh treated plants. In addition, the content of phenols and flavonoids increased due to application of ACh. Content of nitrogen, potassium and calcium increased due to ACh and also alleviated the decline induced due to Ni stress while as the content of Ni was reduced in plants treated with ACh.

Heavy metals mitigation and growth promoting effect of endophytic Agrococcus terreus (MW 979614) in maize plants under zinc and nickel contaminated soil.

Heavy metals such as iron, copper, manganese, cobalt, silver, zinc, nickel, and arsenic have accumulated in soils for a long time due to the dumping of industrial waste and sewage. Various techniques have been adapted to overcome metal toxicity in agricultural land but utilizing a biological application using potential microorganisms in heavy metals contaminated soil may be a successful approach to decontaminate heavy metals soil. Therefore, the current study aimed to isolate endophytic bacteria from a medicinal plant (Viburnum grandiflorum) and to investigate the growth-promoting and heavy metal detoxification potential of the isolated endophytic bacteria Agrococus tereus (GenBank accession number MW 979614) under nickel and zinc contamination. Zinc sulfate and nickel sulfate solutions were prepared at the rate of 100 mg/kg and 50 mg/kg in sterilized distilled water. The experiment was conducted using a completely random design (CRD) with three replicates for each treatment. Inoculation of seeds with A. tereus significantly increased the plant growth, nutrient uptake, and defense system. Treatment T4 (inoculated seeds), T5 (inoculated seeds + Zn100 mg/kg), and T6 (inoculated seeds + Ni 100 mg/kg) were effective, but T5 (inoculated seeds + Zn100 mg/kg) was the most pronounced and increased shoot length, root length, leaf width, plant height, fresh weight, moisture content, and proline by 49%, 38%, 89%, 31%, 113%, and 146%, respectively. Moreover the antioxidant enzymes peroxidase and super oxidase dismutase were accelerated by 211 and 68% in contaminated soil when plants were inoculated by A. tereus respectively. Similarly the inoculation of A. tereus also enhanced maize plants' absorption of Cu, Mn, Ni, Na, Cr, Fe, Ca, Mg, and K significantly. Results of the findings concluded that 100 mg/kg of Zn and Ni were toxic to maize growth, but seed inoculation with A. tereus helped the plants significantly in reducing zinc and nickel stress. The A. tereus strain may be employed as a potential strain for the detoxification of heavy metals.

Transcriptome Analysis Reveals Changes in Whole Gene Expression, Biological Process, and Molecular Functions Induced by Nickel in Jack Pine (Pinus banksiana).

Understanding the genetic response of plants to nickel stress is a necessary step to improving the utility of plants in environmental remediation and restoration. The main objective of this study was to generate whole genome expression profiles of P. banksiana exposed to nickel ion toxicity compared to reference genotypes. Pinus banksiana seedlings were screened in a growth chamber setting using a high concentration of 1600 mg of nickel per 1 kg of soil. RNA was extracted and sequenced using the Illumina platform, followed by de novo transcriptome assembly. Overall, 25,552 transcripts were assigned gene ontology. The biological processes in water-treated samples were analyzed, and 55% of transcripts were distributed among five categories: DNA metabolic process (19.3%), response to stress (13.3%), response to chemical stimuli (8.7%), signal transduction (7.7%) and response to biotic stimulus (6.0%). For molecular function, the highest percentages of genes were involved in nucleotide binding (27.6%), nuclease activity (27.3%) and kinase activity (10.3%). Sixty-two percent of genes were associated with cellular compartments. Of these genes, 21.7% were found in the plasma membrane, 16.1% in the cytosol, 12.4% with the chloroplast and 11.9% in the extracellular region. Nickel ions induced changes in gene expression, resulting in the emergence of differentially regulated categories. Overall, there were significant changes in gene expression with a total 4128 genes upregulated and 3754 downregulated genes detected in nickel-treated genotypes compared to water-treated control plants. For biological processes, the highest percentage of upregulated genes in plants exposed to nickel were associated with the response to stress (15%), the response to chemicals (11,1%), carbohydrate metabolic processes (7.4%) and catabolic processes (7.4%). The largest proportions of downregulated genes were associated with the biosynthetic process (21%), carbohydrate metabolic process (14.3%), response to biotic stimulus (10.7%) and response to stress (10.7%). For molecular function, genes encoding for enzyme regulatory and hydrolase activities represented the highest proportion (61%) of upregulated gene. The majority of downregulated genes were involved in the biosynthetic processes. Overall, 58% of upregulated genes were located in the extracellular region and the nucleus, while 42% of downregulated genes were localized to the plasma membrane and 33% to the extracellular region. This study represents the first report of a transcriptome from a conifer species treated with nickel.

Exogenously applied sodium nitroprusside alleviates nickel toxicity in maize by regulating antioxidant activities and defense-related gene expression.

Nickel (Ni) stress adversely affects plant growth and biomass accumulation, posturing severe menace to crop production and food security. The current study aimed to determine the putative role of sodium nitroprusside (SNP) in mitigating Ni-induced phytotoxicity and identify the underlying defense mechanisms in maize, which are poorly understood. Our findings showed that SNP significantly augmented plant growth, biomass, and photosynthesis-related attributes (Fv/Fm, Fm, qP ETR, and ΦPSII) through diminishing Ni uptake and translocation in root and shoot tissues of maize under Ni stress conditions. In parallel, exogenous SNP substantially relieved maize seedlings from Ni-induced stress by enhancing enzymatic (SOD, CAT, and GPX) and non-enzymatic (phenol and flavonoids) antioxidant defenses and reducing oxidative stress indicators (MDA and H2 O2 ). The results revealed that SNP treatment increased the content of organic osmolyte glycine betaine and the activity of GST, concomitantly with ATP and ionic exchange capacity (including Ca2+ -ATPase and Mg2+ -ATPase), advocating its sufficiency to promote plant growth and avert Ni-induced stress in maize plants. The only exception was the production of organic acids (citric, oxalic, malic, and formic acids), which was reduced as SNP treatment relieved maize seedlings from Ni-induced oxidative damage. The application of SNP also displayed higher expression of defense- and detoxifying-related genes than in control treatments. Together, our data highlighted the mechanism involved in the amelioration of Ni toxicity by SNP; thus, suggesting a potential role of SNP in mitigating the adverse effects of Ni-contaminated soils to boost growth and yield of crop plants, that is, maize.

Morphological and Structural Responses of Albizia lebbeck to Different Lead and Nickel Stress Levels

Lead (Pb) and nickel (Ni) are serious soil pollutants that adversely affect plant growth and development and need to be removed through phytoremediation. The present study aimed to assess the morphological indices of Albizia lebbeck (L.) (Benth.) in relation to anatomical modifications for survival under both Pb and Ni stress. The seedlings of A. lebbeck were established and then subjected to four different concentrations, viz. 0 mM, 25 mM, 50 mM and 75 mM, of Pb and Ni for 14 days in two phases. Morphological traits such as shoot length (70.93%), fresh weight (79.27%), dry weight (83.9%), number of root hairs (65.7%), number of leaves per plant (67.4%) and number of leaflets per plant greatly reduced under Pb or Ni stress. Surprisingly, root length increased rather than decreased with the increase in Pb or Ni concentrations, along with an increase in leaflet width, leaflet length and leaflet area. Moreover, root cortical cell area, metaxylem area and phloem area decreased at 75 mM of Pb and Ni while epidermal thickness and cell area increased. Stem epidermal thickness, cell area and phloem area significantly decreased with the consistent increase in metaxylem area and cortical region thickness under both Pb and Ni stress. Leaf anatomical traits such as midrib thickness, abaxial epidermal thickness and stomatal density and adaxial epidermal thickness and stomatal area significantly increased with increasing Pb or Ni stress. Correlation analysis revealed close relations among morphological and anatomical traits (such as root length with cortical region thickness) for better plant survival under Pb or Ni stress, and a PCA-biplot further verified these correlation analyses. Cluster analyses demonstrated the associations among the morphological and anatomical traits based on different stress levels. Furthermore, we found that the longer exposure (from phase 1 to phase 2) of heavy metals stress is more dangerous for plant survival and can ultimately lead to plant death. Moreover, our results also confirmed that Ni is more harmful or dangerous to plants than Pb at high and moderate concentrations. The anatomical modifications ensured the survival of A. lebbeck in extreme heavy metals stress and therefore unlocked its potential to be used as a natural source of phytoremediation. We also recommend that the genetic potential of A. lebbeck associated with its survival under heavy metal stress be investigated.