Mn Uptake Research Articles

A weak allele of OsNRAMP5 confers moderate cadmium uptake while avoiding manganese deficiency in rice.

Decreasing cadmium (Cd) concentrations in rice grains can effectively reduce potential risks to human health because rice is the major contributor to Cd intake in many diets. Among several genes involved in rice Cd accumulation, the loss of function of OsNRAMP5 is known to be effective in reducing grain concentration by inhibiting root uptake. However, disruption of this gene simultaneously decreases manganese (Mn) uptake because OsNRAMP5 is a major Mn transporter. With the aim of improving Mn uptake in OsNRAMP5 mutants while still restricting the grain Cd concentration below the upper limit of international standards, we identified a novel OsNRAMP5 allele encoding a protein in which glutamine (Q) at position 337 was replaced by lysine (K). The mutant carrying the OsNRAMP5-Q337K allele showed intermediate Cd and Mn accumulation between that of the wild-type and OsNRAMP5-knockout lines, and exhibited more resistance to Mn deficiency than the knockout lines. Different amino acid substitutions at position Q337 significantly affected the Cd and Mn transport activity in yeast cells, indicating that it is one of the crucial sites for OsNRAMP5 function. Our results suggest that the OsNRAMP5-Q337K allele might be useful for reducing grain Cd concentrations without causing severe Mn deficiency in rice cultivars through DNA marker-assisted breeding.

Alleviation of low phosphorus stress in Eucalyptus grandis by arbuscular mycorrhizal symbiosis and excess Mn

Tropical soils are highly-weathered acidic soils and frequently present two intersecting problems that can be detrimental to plant development: low phosphorus (P) and high manganese (Mn) availability. Mn can be phytotoxic, damaging the photosynthetic apparatus and/or competing with other nutrients. Eucalyptus grandis is often cultivated in such soil types and, despite being a tree generally tolerant to Mn excess, P deficiency may exacerbate toxicity. Arbuscular mycorrhizal (AM) fungi are known for their ability to provide P to the host plant in exchange of photosynthates. This symbiosis may also decrease Mn accumulation and overall alleviate metal stress. In a glasshouse experiment, E. grandis plants were grown for seven months in soil with low P availability adjusted to three Mn dose levels (control, 75 and 150 mg kg–1), with (AM) or without (NM) inoculation with Rhizophagus irregularis. We measured biomass, height, flavonoids (anthocyanin/flavonol) and chlorophyll indexes, chlorophyll a fluorescence parameters, AM colonization and Mn, P, Mg, K and Fe concentrations in shoots and roots. All plants presented low biomass production, and shoot P concentrations ranged from 0.13 to 0.52 g kg–1. Mn additions decreased mycorrhizal colonization, but no other negative impacts were seen in E. grandis, indicating that this species is relatively tolerant to excess Mn. At dose 75, shoots accumulated up to 2,000 mg Mn kg–1; however, this amount was not detrimental to most parameters, especially in NM plants, which had higher growth and Mg concentrations while presenting much lower flavonol and anthocyanin contents. At dose 150, plant Mn concentrations were similar to those at 75 Mn, despite higher soil availability, indicating that shoot concentrations around 2,000 mg kg–1 were a threshold for E. grandis under P deficiency. AM colonization intensity and arbuscule abundance were overall low, resulting in no improvements in P nutrition nor reduction of Mn uptake in high Mn treatments. However, AM symbiosis led to higher chlorophyll contents and non-photochemical quenching values, which are important in withstanding abiotic stress. Even though AM fungi inoculation did not improve P uptake, multivariate analysis suggests that the mycorrhizal pathway influenced nutrient acquisition in AM plants. Our results show that in E. grandis Mn excess had an alleviation and a hormetic effect, mitigating P deficiency stress rather than being phytotoxic. AM symbiosis did not improve mineral nutrition, despite providing some benefits involved in stress tolerance.

Calcium and the Ca-ATPase SPCA1 modulate plasma membrane abundance of ZIP8 and ZIP14 to regulate Mn(II) uptake in brain microvascular endothelial cells

Manganese (II) accumulation in human brain microvascular endothelial cells is mediated by the metal-ion transporters ZRT IRT-like protein 8 (ZIP8) and ZRT IRT-like protein 14 (ZIP14). The plasma membrane occupancy of ZIP14, in particular, is increased in cells treated with Mn2+, lipopolysaccharide, or IL-6, but the mechanism of this regulation has not been elucidated. The calcium-transporting type 2C member 1 ATPase, SPCA1, is a Golgi-localized Ca2+-uptake transporter thought to support Golgi uptake of Mn2+ also. Here, we show using surface protein biotinylation, indirect immunofluorescence, and GFP-tagged proteins that cytoplasmic Ca2+ regulates ZIP8- and ZIP14-mediated manganese accumulation in human brain microvascular endothelial cells by increasing the plasma membrane localization of these transporters. We demonstrate that RNAi knockdown of SPCA1 expression results in an increase in cytoplasmic Ca2+ levels. In turn, we found increased cytoplasmic Ca2+ enhances membrane-localized ZIP8 and ZIP14 and a subsequent increase in 54Mn2+ uptake. Furthermore, overexpression of WT SPCA1 or a gain-of-function mutant resulted in a decrease in cytoplasmic Ca2+ and 54Mn2+ accumulation. While addition of Ca2+ positively regulated ZIP-mediated 54Mn2+ uptake, we show chelation of Ca2+ diminished manganese transport. In conclusion, the modulation of ZIP8 and ZIP14 membrane cycling by cytoplasmic calcium is a novel finding and provides new insight into the regulation of the uptake of Mn2+ and other divalent metal ions–mediated ZIP metal transporters.

VrNramp5 is responsible for cadmium and manganese uptake in Vigna radiata roots

As a non-essential mineral, Cadmium inhibits the growth and development of plants. A cultivar (Sulu, SL as wild type) of mungbean is more sensitive to Cd toxicity than its mutant line (20#). However, there is little information about the underlying mechanism. In this study, mutant line (20#) of mungbean exhibited lower Cd accumulation than wild type SL based on the time-course and dose-dependent Cd content in mungbean roots. Meanwhile, compared to 20# roots, the root tips of SL possess a higher capacity for transient Cd influx during exposure to Cd alone or co-treatment with Cd and manganese (Mn). Cd exposure reduced Mn contents of roots in both SL and 20#. Likewise, the addition of Mn in solution or in Cd-polluted soils inhibited Cd uptake in roots. Such reciprocal inhibition shows that Cd competes with Mn for uptake in roots of mungbean. Comparative transcriptomic of roots in SL and 20# were analyzed by Illumina sequencing to elucidate the molecular mechanisms of competitive uptake between Cd and Mn for mungbean. The transcriptomic analysis demonstrated that 28 metal transporters genes showed the log 2 fold changes under Cd stress, including ABC, ZIP, CAX, CCX, MTP, and Nramp family members. Expression abundance of VrABCC15–1 and VrZIP8 genes were significant up-regulated, and VrNramp5 was down-regulated in roots of mungbean under Cd stress. Thus, the three genes were complementarily expressed in Cd sensitive yeast (Δycf1). Expression of VrNramp5 resulted in hypersensitivity to excess Cd owing to the increment of Cd uptake in yeasts during exposure to Cd, but not by VrABCC15–1 or VrZIP8. Expressing-VrNramp5-SL or -VrNramp5–20# yeasts also accumulate higher Mn than that of the expressing-empty vector yeasts. The findings of this study demonstrated that the differences of Cd accumulation between SL and 20# was due to Cd uptake differences, and VrNramp5 is involved in Mn and Cd uptake in mungbean roots.

The Potential of Nitrogen Applied Rapeseed (Brassica napus L) in Remediation of Cadmium Polluted Soil

This study aims to determine the Cd accumulation levels of rapeseed (Brassica napus L.) based on nitrogen (N) (0, 100, 200 and 400 mg kg-1) and Cd (0, 1.5, 3 and 6 mg kg-1) applications to the soil on pot trials conducted under controlled environmental conditions. The highest chlorophyll content was obtained at 400 mg N kg-1 without Cd. The highest dry weight amount in rapeseed was obtained with the application of 100 mg N kg-1 × 1.5 mg Cd kg-1, however, the highest rates of both N and Cd resulted in the lowest dry weight. In 400 mg N kg-1 × 6 mg Cd kg-1 (131 mg Cd kg-1) and 200 mg N kg-1 × 6 mg Cd kg-1 (113.80 mg Cd kg-1) applications, Cd concentration of the rapeseed was determined to be higher than critical Cd hyperaccumulation level. The capacity of Cd uptake and accumulation in rapeseed shoots were enhanced with N applications, thus promoting the phytoextraction of Cd from Cd-contaminated soils. Cadmium rates did not affect Fe, Cu, Mn and Zn uptake levels when N was not applied. However, Cd ratios increased the microelement uptake levels, except Zn, when applied to 100 and 200 N kg-1 ratios as compared to control plants. Eventually, increase in Cd uptake of plants with N fertilization is possible; however, excessive N rates may not result in an increase in rapeseed biomass.

Recovery of microelements from municipal sewage sludge by reed canary grass and giant miscanthus

The aim of the study was to evaluate the content, uptake, and utilization of Al, Mn, Fe, Co, and Mo from municipal sewage sludge by the reed canary grass (RCG) and the giant miscanthus (MG). The impact of sewage sludge on the mass ratios between microelements contained in the plant biomass was analyzed as well. The long-term field experiment consisted in application of four levels of fertilization with sewage sludge: 10, 20, 40, and 60 Mg DM·ha−1. A non-fertilized control object (0 Mg DM·ha−1) was used as well. The miscanthus biomass was characterized by higher content of Al and Mn, whereas higher levels of Fe, Co, and Mo were determined in the reed canary grass biomass. As in the case of the element content, the giant miscanthus was characterized by highest level of Al and Mn uptake, while the highest uptake of Fe, Co, and Mo was exhibited by the reed canary grass. In the group of the analyzed microelements, the giant miscanthus showed the highest the recovery of Mo (47%) followed by Mn (39%), Fe (35%), and Co (15%), and the lowest uptake was determined in the case of Al (5%).

Regulation and Function of Metal Uptake Transporter NtNRAMP3 in Tobacco.

Natural resistance-associated macrophage protein (NRAMP) genes encode proteins with low substrate specificity, important for maintaining metal cross homeostasis in the cell. The role of these proteins in tobacco, an important crop plant with wide application in the tobacco industry as well as in phytoremediation of metal-contaminated soils, remains unknown. Here, we identified NtNRAMP3, the closest homologue to NRAMP3 proteins from other plant species, and functionally characterized it. A NtNRAMP3-GFP fusion protein was localized to the plasma membrane in tobacco epidermal cells. Expression of NtNRAMP3 in yeast was able to rescue the growth of Fe and Mn uptake defective Δfet3fet4 and Δsmf1 mutant yeast strains, respectively. Furthermore, NtNRAMP3 expression in wild-type Saccharomyces cerevisiae DY1457 yeast strain increased sensitivity to elevated concentrations of iron (Fe), manganese (Mn), copper (Cu), cobalt (Co), nickel (Ni), and cadmium (Cd). Taken together, these results point to a possible role in the uptake of metals. NtNRAMP3 was expressed in the leaves and to a lesser extent in the roots of tobacco plants. Its expression occurred mainly under control conditions and decreased very sharply in deficiency and excess of the tested metals. GUS-based analysis of the site-specific activity of the NtNRAMP3 promoter showed that it was primarily expressed in the xylem of leaf blades. Overall, our data indicate that the main function of NtNRAMP3 is to maintain cross homeostasis of Fe, Mn, Co, Cu, and Ni (also Cd) in leaves under control conditions by controlling xylem unloading.

Manganese Uptake to Wheat Shoot Meristems Is Differentially Influenced by Arbuscular Mycorrhiza Fungal Communities Adapted to Acidic Soil

Soil acidity is a strong promoter of the bioavailability of Al, Fe, and Mn, whose concentrations can sometimes reach toxic levels for plants. In agricultural soils, the use of arbuscular mycorrhizal fungi (AMF) has shown a protective influence on wheat growth under Mn toxicity. The intact extraradical mycelium (ERM) promotes faster AMF colonization, leading to a higher wheat shoot weight, lower Mn uptake, and changes in antioxidant enzyme activity. Its effect on the uptake and distribution of plant nutrients according to the developmental stage of shoot organs has seldomly been analyzed. In the present study, Mn, Mg, Ca, and K were quantified by ICP–MS in leaves and apical meristems of wheat grown in soil with two different ERM consortia, developed from the native plants Lolium rigidum (LOL) and Ornithopus compressus (ORN). The ORN treatment induced the highest wheat shoot weights and the lowest Mn levels. In the leaves, no significant differences were detected for Mg, Ca, or K, but in the apical meristems, the ORN treatment slightly lowered the Ca concentration. The AMF associated with ORN was seen to enhance wheat weight partly by protecting the zones of active growth against high Mn levels in Mn toxic soils. The use of ORN in acidic soils with Mn toxicity provides a sustainable alternative and an efficient complement to current farming practices to lower the negative impacts of farming on the environment.

Selenium alleviates physiological traits, nutrient uptake and nitrogen metabolism in rice under arsenate stress.

A green house experiment was conducted to evaluate the efficacy of soil application of selenium (Se) in modulating metabolic changes in rice under arsenic (As) stress. Rice plants were grown over soil amended with sodium arsenate (25, 50 and 100μMkg-1 soil) with or without sodium selenate @ 0.5 and 1mgkg-1 soil in a complete randomized experimental design, and photosynthetic efficiency, nutrient uptake and nitrogen metabolism in rice leaves were estimated at tillering and grain filling stages. Se treatments significantly improved the toxic effects of As on plant height, leaf dry weight and grain yield. Arsenate treatment reduced uptake of Na, Mg, P, K, Ca, Mn, Fe and Zn and lowered chlorophyll, carotenoids and activities of enzymes of nitrogen metabolism (nitrate reductase, nitrite reductase, glutamine synthase and glutamate synthase) in rice leaves at both the stages in a dose-dependent fashion. Se application along with As improved photosynthesis, nutrient uptake and arsenate-induced effects on activities of enzymes of nitrogen metabolism with maximum impact shown by As50 + Se1 combination. Application of Se can modulate photosynthetic efficiency, nutrient uptake and alterations in nitrogen metabolism in rice Cv PR126 due to As stress that helped plants to adapt to excess As and resulted in improved plant growth.

Naturally grown duckweeds as quasi-hyperaccumulators of rare earth elements and yttrium in aquatic systems and the biounavailability of gadolinium-based MRI contrast agents

The use of rare earths and yttrium (REY) in high-technology products is accompanied by their increasing release into the environment. Concerns regarding the (eco-)toxicity and bioaccumulation of these emerging contaminants highlight the need for research on REY uptake by (aquatic) plants.Duckweeds are widespread macrophytes in lentic waters and receive increasing attention as a potential protein-rich food additive. We here provide a baseline dataset for the complete set of REY in naturally grown duckweed assemblages and ambient freshwater and coastal brackish seawater. Our results show that duckweeds strongly bioaccumulate REY and incorporate them at the μg/kg level (dry matter basis). Their shale-normalised (SN) REY patterns are mildly fractionated relative to upper continental crust, regardless of sampling location and season. In contrast, the patterns of ambient waters increase from light to heavy REY (LREY and HREY, resp.) and may show prominent positive anthropogenic GdSN anomalies due to the presence of Gd-based contrast agents (Gd-CAs) applied for magnetic resonance imaging (MRI). The lack of GdSN anomalies in the duckweed assemblages reveals discrimination against the uptake of Gd-CAs by the macrophytes, providing further evidence for the conservative behaviour of these xenobiotics in the environment. High REY concentrations and apparent bulk distribution coefficients between duckweeds and ambient waters of up to 105 show that duckweeds are quasi-hyperaccumulators of REY. Uptake of LREY is up to two orders of magnitude higher than of HREY, possibly due to stronger complexation of HREY with dissolved ligands. The REY closely correlate with Mn but not with Ca, suggesting that uptake of REY and Mn occurs via the same pathway and revealing the negligible role of calcium oxalates. Our study demonstrates that while duckweeds are quasi-hyperaccumulators of REY, there is currently no risk that anthropogenic Gd from MRI contrast agents may enter the food chain via consumption of duckweeds.

Phytotoxicity and Accumulation of Copper-Based Nanoparticles in Brassica under Cadmium Stress.

The widespread use of copper-based nanoparticles expands the possibility that they enter the soil combined with heavy metals, having a toxic effect and posing a threat to the safety of vegetables. In this study, single and combined treatments of 2 mg/L Cd, 20 mg/L Cu NPs and 20 mg/L CuO NPs were added into Hoagland nutrient solution by hydroponics experiments. The experimental results show that copper-based Nanoparticles (NPs) can increase the photosynthetic rate of plants and increase the biomass of Brassica. Cu NPs treatment increased the Superoxide Dismutase (SOD), Peroxidase (POD) and catalase (CAT) activities of Brassica, and both NPs inhibited ascorbate peroxidase (APX) activity. We observed that Cd + Cu NPs exhibited antagonistic effects on Cd accumulation, inhibiting it by 12.6% in leaf and 38.6% in root, while Cd + CuO NPs increased Cd uptake by 73.1% in leaves and 22.5% in roots of Brassica. The Cu content in the shoots was significantly negatively correlated with Cd uptake. The Cd content of each component in plant subcellular is soluble component > cytoplasm > cell wall. Cu NPs + Cd inhibited the uptake of Zn, Ca, Fe, Mg, K and Mn elements, while CuO NPs + Cd promoted the uptake of Mn and Na elements. The results show that copper-based nanoparticles can increase the oxidative damage of plants under cadmium stress and reduce the nutritional value of plants.

Comparative Ionomics and Metabolic Responses and Adaptive Strategies of Cotton to Salt and Alkali Stress.

Soil salinization and alkalization severely inhibit agriculture. However, the response mechanisms of cotton to salt stress or alkali stress are unclear. Ionomics and metabolomics were used to investigate salt and alkali stresses in cotton roots and leaves. Compared with the control, salt-treated and alkali-treated cotton plants showed 51.8 and 53.0% decreases in biomass, respectively. Under salt stress, the concentration of N decreased in roots but increased in leaves, and the concentrations of P and K increased in roots but decreased in leaves. Salt stress inhibited Ca, B, N, and Fe uptake and Mg, K, P, S, and Cu transport, but promoted Mo, Mn, Zn, Mg, K, P, S, and Cu uptake and Mo, Mn, Zn, B, N, and Fe transport. Under alkali stress, the concentrations of N and P in roots and leaves decreased, while the concentrations of K in roots and leaves increased. Alkali stress inhibited P, Ca, S, N, Fe, and Zn uptake and N, P, Mg and B transport, but promoted K, Mn, Cu, Mo, Mg, and B uptake and K, Mn, Cu, Mo, Fe, and Zn transport. Under salt stress in the leaves, 93 metabolites increased, mainly organic acids, amino acids, and sugars, increased in abundance, while 6 decreased. In the roots, 72 metabolites increased, mainly amino acids, organic acids, and sugars, while 18 decreased. Under alkali stress, in the leaves, 96 metabolites increased, including organic acids, amino acids, and sugars, 83 metabolites decreased, including organic acids, amino acids, and sugars; In the roots, 108 metabolites increased, including organic acids, amino acids, and sugars. 83 metabolites decreased, including organic acids and amino acids. Under salt stress, cotton adapts to osmotic stress through the accumulation of organic acids, amino acids and sugars, while under alkali stress, osmoregulation was achieved via inorganic ion accumulation. Under salt stress, significant metabolic pathways in the leaves and roots were associated with amino acid and organic acid metabolism, sugar metabolism was mainly used as a source of energy, while under alkali stress, the pathways in the leaves were related to amino acid and linoleic acid metabolism, β-Oxidation, TCA cycle, and glycolysis were enhanced to provide the energy needed for life activities. Enhancing organic acid accumulation and metabolism in the roots is the key response mechanism of cotton to alkalinity.

Rice performance as influenced by crop establishment methods, green organic mulches and rates of nitrogen fertilization along with liquid Azotobacter chroococcum

The effect of green organic mulches (Sesbania aculeata and Leucaena leucocephala) and nitrogen (N) levels on growth, yield, quality and nutrient uptake of rice (Oryza sativa L.) cultivar “Pusa Basmati 1509” was investigated in aerobic rice (AR) and transplanted rice (TPR). The levels of N were control (N0), 75% recommended dose of N (RDN); and 100% RDN) applied through Chemical fertilizer and Azotobacter chroococcum a liquid biofertilizer. A Field experiment was conducted in split plot design with four main-plot and 5 sub-plot treatments. The main plot consisted of bare soil, Sesbania mulch (10 Mg ha−1, fresh weight-FW), Leucaena mulch (10 Mg ha−1 FW), and TPR; and sub-plot consisted N0; 75% RDN, 100% RDN; 75% RDN+Azotobacter, and 100% RDN+Azotobacter. The highest grain, straw and biological yields (3.84, 6.74 and 11.6 Mg ha−1, respectively) and nutrient uptake were recorded with TPR followed by AR with Leucaena and Sesbania mulch. Grain, straw and biological yield of TPR over bare soil were increased by 31.9, 26.6 and 28.3%, respectively. Uptake of Fe, Zn, Mn and Cu by rice under TPR were 52, 33, 36 and 33% higher, respectively than AR under bare soil. The highest grain, straw, and biological yields (3.86, 7.79 and 11.7 Mg ha−1, respectively) of AR were obtained in 100% RDN + Azotobacter compared to the rest of the treatments. Therefore, the cultivation of AR with Leucaena/Sesbania mulch along with 100% RDN and Azotobacter biofertilizer can be most productive in the study area.

Early-Life Critical Windows of Susceptibility to Manganese Exposure and Sex-Specific Changes in Brain Connectivity in Late Adolescence

BackgroundEarly-life environmental exposures during critical windows (CWs) of development can impact life course health. Exposure to neuroactive metals such as manganese (Mn) during prenatal and early postnatal CWs may disrupt typical brain development, leading to persistent behavioral changes. Males and females may be differentially vulnerable to Mn, presenting distinctive CWs to Mn exposure. MethodsWe used magnetic resonance imaging to investigate sex-specific associations between early-life Mn uptake and intrinsic functional connectivity in adolescence. A total of 71 participants (15–23 years old; 53% female) from the Public Health Impact of Manganese Exposure study completed a resting-state functional magnetic resonance imaging scan. We estimated dentine Mn concentrations at prenatal, postnatal, and early childhood periods using laser ablation–inductively coupled plasma–mass spectrometry. We performed seed-based correlation analyses to investigate the moderating effect of sex on the associations between Mn and intrinsic functional connectivity adjusting for age and socioeconomic status. ResultsWe identified significant sex-specific associations between dentine Mn at all time points and intrinsic functional connectivity in brain regions involved in cognitive and motor function: 1) prenatal: dorsal striatum, occipital/frontal lobes, and middle frontal gyrus; 2) postnatal: right putamen and cerebellum; and 3) early childhood: putamen and occipital, frontal, and temporal lobes. Network associations differed depending on exposure timing, suggesting that different brain networks may present distinctive CWs to Mn. ConclusionsThese findings suggest that the developing brain is vulnerable to Mn exposure, with effects lasting through late adolescence, and that females and males are not equally vulnerable to these effects. Future studies should investigate cognitive and motor outcomes related to these associations.

NRAMP6 and NRAMP1 cooperatively regulate root growth and manganese translocation under manganese deficiency in Arabidopsis.

The essential micronutrient manganese (Mn) in plants regulates multiple biological processes including photosynthesis and oxidative stress. Some Natural Resistance-Associated Macrophage Proteins (NRAMPs) have been reported to play critical roles in Mn uptake and reutilization in low Mn conditions. NRAMP6 was demonstrated to regulate cadmium tolerance and iron utilization in Arabidopsis. Nevertheless, it is unclear whether NRAMP6 plays a role in Mn nutrition. Here, we report that NRAMP6 cooperates with NRAMP1 in Mn utilization. Mutation of NRAMP6 in nramp1 but not in a wild-type background reduces root growth and Mn translocation from the roots to shoots under Mn deficient conditions. Grafting experiments revealed that NRAMP6 expression in both the roots and shoots is required for root growth and Mn translocation under Mn deficiency. We also showed that NRAMP1 could replace NRAMP6 to sustain root growth under Mn deficiency, but not vice versa. Mn deficiency does not affect the transcript level of NRAMP6, but is able to increase and decrease the protein accumulation of NRAMP6 in roots and shoots, respectively. Furthermore, NRAMP6 can be localized to both the plasma membrane and endomembranes including the endoplasmic reticulum, and Mn deficiency enhances the localization of NRAMP6 to the plasma membrane in Arabidopsis plants. NRAMP6 could rescue the defective growth of the yeast mutant Δsmf2, which is deficient in endomembrane Mn transport. Our results reveal the important role of NRAMP6 in Mn nutrition and in the long-distance signaling between the roots and shoots under Mn deficient conditions.

Bio-Priming with Compatible Rhizospheric Microbes Enhances Growth and Micronutrient Uptake of Red Cabbage

Red cabbage is known as the millennium’s functional food, which has a lot of importance in our diet because of the health-promoting ingredients present in it. The current study investigated the synergistic relationship of rhizospheric-competent microbial agents (Trichoderma harzianum, Pseudomonas fluorescens, and Bacillus subtilis) in modulating the performance of red cabbage under the field conditions of Middle Gangetic Plains, India. Growth parameters were studied at three developmental stages, viz., pre-cupping, early head formation, and maturity. Our results suggested that the dual application of T. harzianum + P. fluorescens along with the 75% recommended dose of fertilizers (RDF) increased the number of leaves (24.6), leaf area (537.2 cm2), root length (19.8 cm), and micronutrient uptake (Fe, Mn, and Cu) by head of the crop, whereas the co-inoculation of P. fluorescens and B. subtilis along with 75% RDF enhanced plant spread (39.0 cm), earliness (95.2 days), and Zn uptake. Maximum plant height (28.7 cm) and chlorophyll (SPAD, 77.3) were recorded in 100% RDF (120:60:60 kg ha−1) and the combination of T. harzianum + B. subtilis along with 75% RDF, respectively. Interestingly, consortium (T. harzianum + P. fluorescens) bio-primed plants recorded about 14% higher root length in comparison to plants receiving sole fertilizers. The regression analysis revealed a significant relationship of Fe and Mn uptake with chlorophyll (SPAD) and between Zn uptake and the earliness of the crop. The present study indicated that seedling bio-priming with the dual consortium of efficient bio-agents is a viable strategy to lessen our dependence on chemical fertilizers for improving red cabbage production.

Knockout of OsNRAMP5 enhances rice tolerance to cadmium toxicity in response to varying external cadmium concentrations via distinct mechanisms

OsNRAMP5 is a transporter responsible for cadmium (Cd) and manganese (Mn) uptake and root-to-shoot translocation of Mn in rice plants. Knockout of OsNRAMP5 is regarded as an effective approach to minimize Cd uptake and accumulation in rice. It is vital to evaluate the effects of knocking out OsNRAMP5 on Cd and Mn accumulation, as well as Cd tolerance of rice plants in response to varying environmental Cd concentrations, and to uncover the underlying mechanism, which until now, has remained largely unexplored. This study showed that knockout of OsNRAMP5 decreased Cd uptake, but simultaneously facilitated Cd translocation from roots to shoots. The effect of OsNRAMP5 knockout on reducing root Cd uptake weakened, however its effect on improving root-to-shoot Cd translocation was constant with increasing environmental Cd concentrations. As a result, its mutation dramatically reduced Cd accumulation in shoots under low and moderate Cd stress, but inversely increased that under high Cd conditions. Interestingly, Cd tolerance of its knockout mutants was persistently enhanced, irrespective of lower or higher Cd concentrations in shoots, compared with that of wild-type plants. Knockout of OsNRAMP5 mitigated Cd toxicity by dramatically diminishing Cd uptake at low or moderate external Cd concentrations. Remarkably, its knockout effectively complemented deficient mineral nutrients in shoots, thereby indirectly enhancing rice tolerance to severe Cd stress. Additionally, its mutation conferred preferential delivery of Mn to young leaves and grains. These results have important implications for the application of the OsNRAMP5 mutation in mitigating Cd toxicity and lowering the risk of excessive Cd accumulation in rice grains.

Cadmium Pollution Impairs Maize Growth and Uptake of Cationic Essential Nutrients

Human population is anticipated to increase to 9.8 billion by 2050 and this increase causes a more intensive agricultural production. The soils are polluted as the farming activities are intensified. Fertilizers and the pesticides that are used in agriculture and the imbalanced industrialization cause heavy metals to move into the soil thereby creating soil-environmental pollution. Cadmium (Cd), one of the heavy metals, is also present in the biosphere, enters the soil as a result of natural processes and anthropogenic activities, exerting toxic effects on agricultural products, food chain and living organisms. This highly toxic and dangerous metal has come to the fore with its important role in environmental pollution due to its various usage areas. In this study, the effects of three different Cd doses on the cationic macro and micronutrient content of maize plant was investigated. Cadmium application at 2.5 and 5.0 mg kg-1 decreased shoot dry matter by % 10.8 and % 20.0 respectively compared with control treatment. While the highest macro and micronutrient contents were obtained in the control treatment, the lowest values were obtained in the Cd5 treatment. Cadmium applications were not statistically significant in shoot K, Mg and Ca concentrations but significantly decreased K and Ca contents. Compared with the control treatment, Cd applications at 2.5 and 5.0 mg/kg were determined to decrease the K content by % 9.9 and % 18.4 and Ca content by 17.7% and 21.3% respectively. When the Cd concentration and content are determined, the highest values were found to be in the Cd5 treatment. Consequently, increased Cd accumulation in shoots was determined to be associated with decreases in K, Ca, Cu, Zn, Fe and Mn uptake of maize plant. Therefore, close monitoring of nutritional problems that can potentially occur in agricultural areas contaminated with Cd might be beneficial for the evaluation of different solution proposals

Genome-Wide Identification and Expression Profile Reveal Potential Roles of Peanut ZIP Family Genes in Zinc/Iron-Deficiency Tolerance.

Zinc/iron-regulated transporter-like protein (ZIP) family genes play crucial roles in metal uptake and transport in plants. However, little is known about their functions in peanut. Here, genome-wide analysis identified 30 peanut AhZIP genes that were divided into four classes. Most AhZIPs experienced whole-genome or segmental duplication. AhZIP proteins harbored 3–8 transmembrane domains and a typical ZIP domain, showing considerable homology with BbZIP from Bordetella bronchiseptica. Clustered AhZIPs generally share similar gene/protein structures; however, unique features were found in AhIRT1.2, AhZIP1.2, AhZIP3.5 and AhZIP7.8. RNA-seq data revealed that AhZIP2.1/2.2, AhZIP4.1/4.2 and AhZIP11.1/11.2 were highly and preferentially expressed in roots, nodule and reproductive tissues. RT-qPCR analysis indicated that transcriptional responses of AhZIPs to Fe/Zn deficiency are cultivar dependent. The expressions of AhIRT1.1, AhIRT1.2 and AhZIP6.1 were closely related to Fe uptake and translocation. AhIRT1.1 and AhZIP7.2 expression were significantly correlated with Zn accumulation. The expression of AhIRT1.1, AhIRT1.2, AhZIP3.6, AhZIP6.1 and AhZIP11.1 was associated with Mn uptake and translocation. The results confirmed that AhZIP genes play crucial roles in the uptake and transport of Fe, Zn and Mn in peanut, providing clues to further functionally characterize AhZIP genes in the future.

Longitudinal manganese-enhanced magnetic resonance imaging of neural projections and activity.

Manganese-enhanced magnetic resonance imaging (MEMRI) holds exceptional promise for preclinical studies of brain-wide physiology in awake-behaving animals. The objectives of this review are to update the current information regarding MEMRI and to inform new investigators as to its potential. Mn(II) is a powerful contrast agent for two main reasons: (1) high signal intensity at low doses; and (2) biological interactions, such as projection tracing and neural activity mapping via entry into electrically active neurons in the living brain. High-spin Mn(II) reduces the relaxation time of water protons: at Mn(II) concentrations typically encountered in MEMRI, robust hyperintensity is obtained without adverse effects. By selectively entering neurons through voltage-gated calcium channels, Mn(II) highlights active neurons. Safe doses may be repeated over weeks to allow for longitudinal imaging of brain-wide dynamics in the same individual across time. When delivered by stereotactic intracerebral injection, Mn(II) enters active neurons at the injection site and then travels inside axons for long distances, tracing neuronal projection anatomy. Rates of axonal transport within the brain were measured for the first time in "time-lapse" MEMRI. When delivered systemically, Mn(II) enters active neurons throughout the brain via voltage-sensitive calcium channels and clears slowly. Thus behavior can be monitored during Mn(II) uptake and hyperintense signals due to Mn(II) uptake captured retrospectively, allowing pairing of behavior with neural activity maps for the first time. Here we review critical information gained from MEMRI projection mapping about human neuropsychological disorders. We then discuss results from neural activity mapping from systemic Mn(II) imaged longitudinally that have illuminated development of the tonotopic map in the inferior colliculus as well as brain-wide responses to acute threat and how it evolves over time. MEMRI posed specific challenges for image data analysis that have recently been transcended. We predict a bright future for longitudinal MEMRI in pursuit of solutions to the brain-behavior mystery.