Zinc Stress Research Articles

Serum levels of iron, zinc, selenium, copper and oxidative stress in hypertensive patients: A comparative study of age-related changes in the governorate of Basrah, Iraq

Hypertension is the force of blood through blood vessels, where the heart works harder and blood vessels are under more pressure. The relationship between trace element levels and oxidative stress in hypertension is under investigation, with conflicting results. This study aimed to determine the relationship between concentrations of certain antioxidant trace elements (iron, zinc, selenium, and copper) and protein carbonyl concentration as an indicator of oxidative stress in the serum of hypertensive patients compared to the control group in Basra, Iraq, according to age. The study included 100 hypertensive patients (44 males and 56 females) compared to 50 healthy individuals (25 males and 25 females). Patients were divided into three age groups: 35–45, 46–56, and over 57 years. The study showed a significant decrease (p<0.001) in the mean concentration of all selected elements in the patients' serum compared to the control group. Conversely, the mean protein carbonyl level showed a significant increase (p<0.001) in patients compared to the control group. Trace element concentrations decreased in patients with increasing age, while carbonyl protein levels increased, especially in the third age group. The study also showed a significant negative correlation between protein carbonyl level and all trace elements at p<0.001. These results suggest that hypertension is associated with an imbalance in oxidative stress and trace elements. Monitoring trace element intake may help reduce oxidative stress and improve overall health in individuals with hypertension, especially with advancing age, by restoring the balance of essential elements and antioxidants in the body.

Zinc/Iron-Regulated Transporter-like Protein CsZIP4 Enhances Zinc and Nitrogen Uptake and Alleviates Zinc Stresses with Nitrogen Supply in Camellia sinensis.

Zinc (Zn) and nitrogen (N) are the two crucial nutrients for tea plant growth and development and contribute to the quality formation of tea fresh leaves. In this study, a zinc/iron-regulated transporter-like protein 4 gene (i.e., CsZIP4) was functionally characterized. Expression profiling showed that CsZIP4 could be induced by Zn stresses and a N deficiency. Heterologous expression of CsZIP4 in yeast revealed that CsZIP4 possessed the capacity for Zn transport but not ammonium. Moreover, CsZIP4 overexpression in Arabidopsis thaliana promoted Zn and N uptake and transport and contributed to alleviate Zn stresses by collaborating with N supply, which might be interrelated to the expression of N or Zn metabolism-related genes, such as AtNRT1.1 and AtZIP4. Additionally, CsZIP4 was localized in the plasma membrane and chloroplast, which was helpful in maintaining cellular homeostasis under a Zn excess. Furthermore, silencing of CsZIP4 in tea plants by virus-induced gene silencing increased the chlorophyll content but decreased the Zn content. Finally, the yeast one-hybrid assay demonstrated that CsbZIP2 bound to the CsZIP4 promoter. These results will shed light on the functions of CsZIP4 in the N and Zn interaction in tea plants.

Association of serum zinc with mineral stress in chronic kidney disease.

The excessive cardiovascular mortality of patients with chronic kidney disease (CKD) could be linked to mineral stress, the biological consequence of calcium-phosphate nanoparticle exposure. This study investigated whether zinc is associated with mineral stress markers in CKD. Zinc and T50 (serum calcification propensity) as well as hydrodynamic radius of secondary calciprotein particles (CPP2) were measured in blood donors and CKD patients with/out dialysis. Serum zinc concentrations and T50 were reduced, while CPP2 radius was increased in CKD patients. Serum zinc levels positively correlated with T50 and inversely correlated with CPP2 radius. In a hierarchical linear regression model, T50 was associated with age, calcium, phosphate, magnesium and albumin. Addition of zinc significantly improved prediction of the model, confirming an additional contribution of zinc to T50. Similar observations were made for the association of zinc and CPP2 radius, but spiking experiments indicated that zinc may stronger modify T50 than CPP2 radius. Also, urinary zinc excretion was increased in patients with kidney disease and correlated to T50 and CPP2 radius. Serum zinc further correlated with markers of arterial stiffness in blood donors and CKD patients, but these associations did not remain significant in a multivariate linear regression model. Reduced serum zinc levels in CKD appear directly linked to lower T50 and associated with larger CPP2 radius. Further studies on the associations of zinc and mineral stress as well as putative therapeutic benefits of zinc supplementation are required.

Genome-wide identification of metal tolerance protein genes in Quercus dentata and their roles in response to various heavy metal stresses

Metal tolerance protein (MTP) is a cation transporter that plays an important role in tolerance to heavy metal stress. However, thus far, there has been no genome-wide investigation of the MTP gene family in Quercus plants. Quercus dentata is one of the main constructive species of forest in northern China. It has strong tolerance to a variety of heavy metal stresses. In this study, 25 MTPs were identified from the Q. dentata genome and classified into three subfamilies and seven groups according to their sequence characteristics and phylogenetic relationships. Both tandem and segmental duplication events contributed to the expansion of the QdMTP gene family. Interestingly, all 10 tandem duplication events contributed to the expansion of the Mn-CDF subfamily. The expression of Mn-CDF subfamily members in different organs and tissues of Q. dentata was different, and they responded differently to manganese, iron, zinc and cadmium stress treatments. QdMTP10.7, a member of the Mn-CDF subfamily, enhanced yeast growth under manganese, zinc and iron stresses. The subcellular localization in tobacco leaf epidermis cells showed that QdMTP10.7 was located in vacuoles. These data generated from this study provide an important foundation to elucidate the biological roles of QdMTP genes related to heavy metal tolerance in Q. dentata.

AcNRZ1, an endoplasmic reticulum-localized NAC transcription factor in kiwifruit, enhances zinc stress tolerance in Arabidopsis

The trace element zinc (Zn) is involved in various biological processes in plant, yet its excessive accumulation can result in plant toxicity. In this study, we unveiled a novel NAC transcription factor, AcNRZ1, in kiwifruit, and qRT-PCR analysis showed that the expression of AcNRZ1 can be up-regulated by Zn stress. Furthermore, Zn stress induces the translocation of AcNRZ1 from endoplasmic reticulum (ER) to nucleus. Overexpression of AcNRZ1 in Arabidopsis imparts tolerance and elevates the germination rates under Zn stress. Subsequent studies have demonstrated that the overexpression of AcNRZ1 facilitates the transport of Zn ions from the root to the leaf and enhances the Zn detoxification process in the vacuole by upregulating the expression of the Zn transport-related gene HMA4, as well as Zn detoxification-related genes including MTP1/3/5, GSH1, and PCS1. Additionally, overexpression of AcNRZ1 in Arabidopsis stimulates the expression of antioxidant enzyme related genes (SOD1 and CAT1), thereby leading to reduced accumulation of reactive oxygen species and ultimately enhancing tolerance to Zn stress. These findings suggest that AcNRZ1 influences plant response to Zn stress by modulating Zn ion transport, promoting detoxification processes, and regulating the accumulation of reactive oxygen species, thereby conferring plant tolerance to Zn stress.

Genomic Analysis of Cronobacter condimenti s37: Identification of Resistance and Virulence Genes and Comparison with Other Cronobacter and Closely Related Species.

Cronobacter condimenti are environmental commensals that have not been associated with any clinical infections. To date, they are the least understood and described Cronobacter species within the genus. The objective of this study was to use a draft genome sequence (DGS) of the Cronobacter condimenti strain s37 to screen for genes encoding for antibiotic resistance, virulence, response to environmental stress, and biofilm formation. The strain was isolated in Poland from commercial small radish sprouts. This is the second genome of this species available in the GenBank database. The comparative genome analysis (cgMLST) of C. condimenti s37 with other Cronobacter spp. including the pathogenic species C. sakazakii and the plant-associated closely related genera Franconibacter and Siccibacter was also performed. The assembled and annotated genome of the C. condimenti s37 genome was 4,590,991 bp in length, with a total gene number of 4384, and a GC content of 55.7%. The s 37 genome encoded for genes associated with resistance to stressful environmental conditions (metal resistance genes: zinc, copper, osmotic regulation, and desiccation stress), 17 antimicrobial resistance genes encoding resistance to various classes of antibiotics and 50 genes encoding for the virulence factors. The latter were mainly genes associated with adhesion, chemotaxis, hemolysis, and biofilm formation. Cg-MLST analysis (3991 genes) revealed a greater similarity of C. condimenti s37 to S. turicensis, F. pulveris, and C. dublinensis than to other species of the genus Cronobacter. Studies on the diversity, pathogenicity, and virulence of Cronobacter species isolated from different sources are still insufficient and should certainly be continued. Especially the analysis of rare strains such as s37 is very important because it provides new information on the evolution of these bacteria. Comparative cgMLST analysis of s37 with other Cronobacter species, as well as closely related genera Franconibacter and Siccibacter, complements the knowledge on their adaptability to specific environments such as desiccation.

Kosakonia arachidis: Shielding Vigna radiata in metal-stressed Hydroponics

The process of modernization and industrialization has indeed heightened environmental toxicity. Deterioration of plant growth and nutrient uptake has resulted in adverse effects on human health. Heavy metals are the most prominent pollutants. Elevated levels of heavy metals can surpass essential elements, leading to deficiencies in plant nutrition and hindering growth. The objective of the study was to extract bacteria that are resistant to zinc and cadmium from fields located in close proximity to the Malviya Nagar industrial zone in Jaipur. After collecting a soil sample, colonies were isolated on nutrient agar medium with varying amounts of heavy metals. Characterization of well-defined colonies was conducted using morphological and biochemical methods, and identification of resistant bacteria was performed using advanced bacterial isolation software (ABIS). Azohydromonas lata, Kosakonia arachidis, Pseudomonas fluorescens, and Pseudomonas aeruginosa were the prominent bacterial species found to have a similarity value over 90%. Among all the bacteria that were identified, Kosakonia arachidis was selected for additional investigation due to the scarcity of studies conducted on this bacterium for the purpose of mitigating heavy metal contamination from soil. The study aimed to assess its capacity to enhance the development of mung beans in non-circulating hydroponic systems under zinc and cadmium stress conditions. The presented study demonstrates the remarkable capacity of Kosakonia arachidis to facilitate plant growth in environments characterized by zinc concentrations of 1000 ppm and cadmium concentrations of 300 ppm. This characteristic renders it a highly promising and pragmatic choice for biofertilizer utilization in plants experiencing stress caused by heavy metals.

Fate of antibiotic resistance genes and EPS defence mechanisms during simultaneous denitrification and methanogenesis, coupled with the biodegradation of multiple antibiotics under zinc stress

High-strength nitrogen and antibiotics-containing wastewater can be efficiently eliminated by simultaneous denitrification and methanogenesis (SDM). Heavy metals and antibiotics are two critical factors that can lead to horizontal transfer of antibiotic resistance genes (ARGs), which can be simultaneously detected in wastewater. Unfortunately, the impacts of heavy metals on SDM and antibiotic biodegradation have not been fully elucidated. Herein, the effects of SDM and multiple antibiotics biodegradation, extracellular polymeric substances (EPSs) and protein response mechanisms, and ARG fate under Zn(II) stress were comprehensively evaluated. The results indicated that a high level of Zn(II) (≥5 mg/L) stress significantly decreased the degradation rate of multiple antibiotics and suppressed denitrification and methanogenesis. In addition, Zn(II) exposure prompted the liberation of proteins from microbes into the EPSs, and the combination of EPSs with small molecules quenched the original fluorescent components and destroyed the protein structure. The dominant proteins can bind to both Zn(II) and multiple antibiotics through several types of chemical interactions, including metallic and hydrogen bonds, hydrophobic interactions, and salt bridges, relieving the toxicity of harmful substances. Moreover, metagenomic sequencing revealed that the abundance of zinc resistance genes (Zn-RGs), ARGs (mainly tetracyclines), and mobile genetic elements (MGEs) increased under Zn(II) stress. Mantel test illustrated that the ARGs mecD, tetT, and tetB(60) were most affected by MGEs. Moreover, molecular network analysis revealed that several MGEs can bridge metal resistance genes (MRGs) and ARGs, facilitating the horizontal transfer of ARGs. This study provides theoretical guidance for the environmental risk control of antibiotics-containing wastewater treated by an SDM system.

Physiological responses and lipid accumulation of freshwater microalgae Chlorella sorokiniana under short-term zinc stress in water solution

As a potential toxic element, zinc exhibits strong environmental mobility and bioavailability, rendering it a subject of profound concern as a highly toxic pollutant. In this study, the toxic effects of divalent zinc ion (Zn2+) with high concentrations at 5, 10, 15, 20, and 25 mg/L on the physiological states of Chlorella sorokiniana were investigated, including growth inhibition, photosynthesis, oxidative damage, and lipid accumulation. The results unequivocally revealed a substantial inhibition of C. sorokiniana growth in response to above 5 mg/L Zn2+ exposure. The photosynthetic activity and photosynthetic pigment content of C. sorokiniana declined with the increase of Zn2+. However, the photosynthetic activity slowly recovered after 72 h of exposure. Zn2+ induced a rapid increase in reactive oxygen species (ROS) within the microalgae, subsequently stimulating superoxide dismutase activity. Nevertheless, the uneliminated excess ROS disrupted the cell membrane, leading to the production of malondialdehyde. Furthermore, Zn2+ at concentrations of 5 and 20 mg/L positively affected the lipid accumulation, resulting in the highest 4.10 mg/L/d lipid production.

Screening of Bread and Durum Wheat Varieties on Yield and Nutritional Quality for Their Tolerance to Zinc Stress

ABSTRACT Zinc (Zn) deficiency is one of the most prevalent micronutrient deficiencies and is mostly brought on by a diet high in cereal grains with low Zn contents. In order to screen prominent bread (12 varieties) and durum (6 varieties) wheat varieties grown under Zn deficient (control) and sufficient (Zn @ 25 mg kg−1 as soil) condition and a pot experiment was conducted in the screen house of the Department of Soil Science, Chaudhary Charan Singh Haryana Agricultural University, Hisar. In the Zn deficient and sufficient soil, the highest yield was observed in HD-2967 (14.57 & 16.13 g/pot) and PWD-291 (8.68 & 11.70 g/pot) of bread and durum wheat, respectively. In Zn-deficient soil, the highest total protein content and Zn content in grain were observed in DBW-88 (8.17 & 26.50%) and PWD-291 (8.42 & 26.52%) of bread and durum wheat, respectively. All the bread wheat varieties were found to be semi tolerant, i.e. the percentage increase in yield was in the category of 10–25% except WH-52 and RAJ-3765 where increase in yield was more than 25%. The maximum increase in yield was found 28.91% in the WH-542 and the minimum increase (10.70%) in the HD-2967 wheat varieties. For durum wheat, two varieties (WH-912 &WHD-943) were found to be semi tolerant, i.e. the percentage increase in yield was in the category of 10–25%. In conclusion, it was determined that this study is helpful for creating methods for micronutrient biofortification using various wheat varieties in south-central Asia.

Mechanism of zinc stress on magnesium deficiency in rice plants (Oryza sativa L.): Insights from magnesium isotopes

Magnesium (Mg) and zinc (Zn) are essential nutrients for plants. Mg deficiency often occurs in rice plants grown in Zn-polluted soil. However, the mechanism for this correlation is unclear. Here, we performed culture experiments on rice plants (Oryza sativa L.) and used Mg isotopes to investigate mechanisms of Zn stress on plant Mg deficiency. Our results show that excess Zn can significantly reduce the uptake of Mg in rice tissues. The root displays positive Δ26Mgplant-nutrient values (δ26Mgplant-δ26Mgnutrient; 1.90 ‰ to 2.06 ‰), which suggests that Mg enters the root cells mainly via Mg-specific transporters rather than non-selective diffusion. The decreased Δ26Mgplant-nutrient values with increasing Zn supply can be explained by the competition between Zn and Mg, both of which combine with same transporters in roots. In contrast, the shoots (stem and leaf) display much lower δ26Mg values than roots, which suggests that the transport of Mg from roots to aerial biomass is mainly via free Mg ions, during which Zn cannot competitively inhibit the movement of Mg. Our study suggests that the Mg deficiency in rice plants can be caused by high Zn-levels in soils and highlights the necessity of soil Zn-remediation in solving Mg deficiency problems in rice plants.

Expression of Concern: The effect of gibberellic acid on wheat growth, and nutrient uptake under combined stress of cerium, zinc and titanium dioxide nanoparticles (Chemosphere, Volume 336, September 2023, 139199)

Expression of Concern: The effect of gibberellic acid on wheat growth, and nutrient uptake under combined stress of cerium, zinc and titanium dioxide nanoparticles (Chemosphere, Volume 336, September 2023, 139199)

CFTR is required for zinc-mediated antibacterial defense in human macrophages

Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion transporter required for epithelial homeostasis in the lung and other organs, with CFTR mutations leading to the autosomal recessive genetic disease CF. Apart from excessive mucus accumulation and dysregulated inflammation in the airways, people with CF (pwCF) exhibit defective innate immune responses and are susceptible to bacterial respiratory pathogens such as Pseudomonas aeruginosa. Here, we investigated the role of CFTR in macrophage antimicrobial responses, including the zinc toxicity response that is used by these innate immune cells against intracellular bacteria. Using both pharmacological approaches, as well as cells derived from pwCF, we show that CFTR is required for uptake and clearance of pathogenic Escherichia coli by CSF-1-derived primary human macrophages. CFTR was also required for E. coli-induced zinc accumulation and zinc vesicle formation in these cells, and E. coli residing in macrophages exhibited reduced zinc stress in the absence of CFTR function. Accordingly, CFTR was essential for reducing the intramacrophage survival of a zinc-sensitive E. coli mutant compared to wild-type E. coli. Ectopic expression of the zinc transporter SLC30A1 or treatment with exogenous zinc was sufficient to restore antimicrobial responses against E. coli in human macrophages. Zinc supplementation also restored bacterial killing in GM-CSF-derived primary human macrophages responding to P. aeruginosa, used as an in vitro macrophage model relevant to CF. Thus, restoration of the zinc toxicity response could be pursued as a therapeutic strategy to restore innate immune function and effective host defense in pwCF.

Natural resistance-associated macrophage proteins are involved in tolerance to heavy metal Cd2+ toxicity and resistance to bacterial wilt of peanut (Arachis hypogaea L.)

Peanut (Arachis hypogaea L.) is one of the most important oil and industrial crops. However, heavy-metal pollution and frequent soil diseases, poses a significant threat to the production of green and healthy peanuts. Herein, we investigated the effects of heavy metal Cd2+ toxicity to the peanuts, and screened out two peanut cultivars H108 and YZ 9102 with higher Cd2+-tolerance. RNA-seq revealed that Natural resistance-associated macrophage proteins (NRAMP)-like genes were involved in the Cd2+ stress tolerance in H108. Genome-wide identification revealed that 28, 13 and 9 Nramp-like genes existing in the A. hypogaea, A. duranensis and A. ipaensis, respectively. The 50 peanut NRAMP genes share conserved architectural characters, and they were classified into two groups. Expressions of AhNramps, particularly AhNramp4, AhNramp12, AhNramp19, and AhNramp25 could be greatly induced by not only cadmium toxicity, but also copper and zinc stresses. The expression profiles of AhNramp14, AhNramp16 and AhNramp25 showed significant differences in the H108 (resistance) and H107 (susceptible) under the infection of bacterial wilt. In addition, we found that the expression profiles of AhNramp14, AhNramp16, and AhNramp25 were greatly up- or down-regulated by the application of exogenous salicylic acid, methyl jasmonate, and abscisic acid. The AhNramp25, of which expression was affected by both heavy metal toxicity and bacterial wilt infection, were selected as strong candidate genes for peanut stress breeding. Our findings will provide an additional information required for further analysis of AhNramps involved in tolerance to heavy metal toxicity and resistance to bacterial wilt of peanut.

Zinc and copper toxicity in basil (Ocimum basilicum L.) seedlings: Role of melatonin in mitigating stress

The effects of melatonin (MT) on the growth and antioxidant responses of basil (Ocimum basilicum L.) exposed to copper and zinc excess stress are investigated. For this purpose, seedlings were exposed to different concentrations of copper oxide (0, 50 and 150 µM), zinc oxide (0, 50 and 100 µM) and melatonin (0 and 100 µM) for 14 days. Growth and biochemical parameters, the activity of some antioxidant enzymes, and phenylalanine ammonia lyase (PAL) and some of the main nutritional elements in the shoot and root of seedlings were measured. The results of this study showed that the excess of copper (Cu 50 and 150 µM) and zinc (Zn 50 and 100 µM) causes a decrease in growth, and a higher oxidative stress indicator such as hydrogen peroxide and malondialdehyde (MDA) content. The homeostasis balance of mineral nutrition of basil seedlings was also disrupted under copper and zinc stress. Melatonin treatment in Cu, Zn stressed seedlings improved growth parameters by reducing the levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA) and increasing the activity of PAL and antioxidant enzymes. Melatonin also regulated the distribution of minerals in basil seedlings under Cu and Zn stress conditions. The results of this research showed that MT can improve the tolerance of basil seedlings against copper and zinc stress by modulate growth and antioxidant responses and regulating mineral nutrition.

The differential expressions of aquaporins underline the diverse strategies of cucumber and tomato against salinity and zinc stress.

Salinity and excess zinc are two main problems that have limited agriculture in recent years. Aquaporins are crucial in regulating the passage of water and solutes through cells and may be essential for mitigating abiotic stresses. In the present study, the adaptive response to moderate salinity (60 mM NaCl) and excess Zn (1 mM ZnSO4 ) were compared alone and in combination in Cucumis sativus L. and Solanum lycopersicum L. Water relations, gas exchange and the differential expression of all aquaporins were analysed. The results showed that cucumber plants under salinity maintained the internal movement of water through osmotic adjustment and the overexpression of specific PIPs aquaporins, following a "conservation strategy". As tomato has a high tolerance to salinity, the physiological parameters and the expression of most aquaporins remained unchanged. ZnSO4 was shown to be stressful for both plant species. While cucumber upregulated 7 aquaporin isoforms, the expression of aquaporins increased in a generalized manner in tomato. Despite the differences, water relations and transpiration were adjusted in both plants, allowing the RWC in the shoot to be maintained. The aquaporin regulation in cucumber plants facing NaCl+ZnSO4 stress was similar in the two treatments containing NaCl, evidencing the predominance of salt in stress. However, in tomato, the induced expression of specific isoforms to deal with the combined stress differed from independent stresses. The results clarify the key role of aquaporin regulation in facing abiotic stresses and their possible use as markers of tolerance to salinity and heavy metals in plants.

Assessment of Drought and Zinc Stress Tolerance of Novel Miscanthus Hybrids and Arundo donax Clones Using Physiological, Biochemical, and Morphological Traits.

High-yield potential perennial crops, such as Miscanthus spp. and Arundo donax are amongst the most promising sources of sustainable biomass for bioproducts and bioenergy. Although several studies assessed the agronomic performance of these species on diverse marginal lands, research to date on drought and zinc (Zn) resistance is scarce. Thus, the objective of this study was to investigate the drought and Zn stress tolerance of seven novel Miscanthus hybrids and seven Arundo clones originating from different parts of Italy. We subjected both species to severe drought (less than 30%), and Zn stress (400 mg/kg-1 of ZnSO4) separately, after one month of growth. All plants were harvested after 28 days of stress, and the relative drought and Zn stress tolerance were determined by using a set of morpho-physio-biochemical and biomass attributes in relation to stress tolerance indices (STI). Principal component analysis (PCA), hierarchical clustering analysis (HCA) and stress tolerance indices (STI) were performed for each morpho-physio-biochemical and biomass parameters and showed significant relative differences among the seven genotypes of both crops. Heatmaps of these indices showed how the different genotypes clustered into four groups. Considering PCA ranking value, Miscanthus hybrid GRC10 (8.11) and Arundo clone PC1 (11.34) had the highest-ranking value under both stresses indicating these hybrids and clones are the most tolerant to drought and Zn stress. In contrast, hybrid GRC3 (-3.33 lowest ranking value) and clone CT2 (-5.84) were found to be the most sensitive to both drought and Zn stress.

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.

Toxicity effects of zinc supply on growth revealed by physiological and transcriptomic evidences in sweet potato (Ipomoea batatas (L.) Lam)

Zinc toxicity affects crop productivity and threatens food security and human health worldwide. Unfortunately, the accumulation patterns of zinc and the harmful effects of excessive zinc on sweet potato have not been well explored. In the present research, two genotypes of sweet potato varieties with different accumulation patterns of zinc were selected to analyze the effects of excessive zinc on sweet potato via hydroponic and field cultivation experiments. The results indicated that the transfer coefficient was closely related to the zinc concentration in the storage roots of sweet potato. Excessive zinc inhibited the growth of sweet potato plants by causing imbalanced mineral concentrations, destroying the cellular structure and reducing photosynthesis. Furthermore, a total of 17,945 differentially expressed genes were identified in the two genotypes under zinc stress by transcriptomic analysis. Differentially expressed genes involved in the absorption and transport of zinc, defense networks and transcription factors played important roles in the response to zinc stress. In conclusion, this study provides a reference for the selection of sweet potato varieties in zinc contaminated soil and lays a foundation for investigating the tolerance of sweet potato to excessive zinc, which is meaningful for environmental safety and human health.

Cloning and biological function analysis of Nramps in blueberry

The natural resistance-associated macrophage protein (Nramp) family comprises crucial membrane transport proteins that play vital roles in the transport and reuse of heavy metal ions in plants. Limited information is currently available on the Nramp family in blueberry (Vaccinium spp.; Vc). Elucidation of the mechanism underlying mineral-element deficiency and heavy metal toxicity in blueberry is essential for the sustainable development of the blueberry industry. In this study, three Nramp genes (VcNramp4, VcNramp6, and VcNramp8.2) were cloned and identified from blueberry, and their functions were analyzed in transgenic Arabidopsis thaliana and yeast. Sequence analysis showed that the VcNramp genes encoded 321–455 amino acids and contained 6–8 transmembrane structural domains. Expression analysis showed that VcNramp genes were significantly up-regulated under iron (Fe) deficiency. The expression of VcNramp genes was most significantly up-regulated in the roots, by 2.05-fold relative to the control group. VcNramp4 and VcNramp6 expression in yeast and A. thaliana alleviated Fe deficiency stress. Interestingly, yeast expressing VcNramp6 showed a 1.13- to 1.38-fold increase in Fe accumulation at different medium pH levels, which was significantly higher than that of yeast expressing the other VcNramp genes. All VcNramp genes respond to changes in Fe ion concentration. Among them, VcNramp6 can effectively ameliorate Fe deficiency symptoms in plants. The expression of VcNramp genes exhibited distinct tissue specificity. Notably, the expression levels of VcNramp6 and VcNramp8.2 in the stems was only 2 %–10 % of that in the roots. The results illustrated the Fe nutrient inefficiency of blueberry. Furthermore, all identified VcNramp genes responded to mild zinc or cadmium stress, but their expression levels decreased under severe zinc or cadmium stress.