Mn Treatment Research Articles

Improving Soil Fertility and Wheat Yield by Tillage and Nitrogen Management in Winter Wheat–Summer Maize Cropping System

Soil degradation and high environmental costs impede agricultural production in North China. A 6-year field experiment was conducted to determine the effects of tillage practice and nitrogen application rate on changes in soil fertility and wheat yield. Four tillage systems (rotary tillage without maize straw return through 6 years, RT; rotary tillage with maize straw return through 6 years, RS; deep tillage with maize straw return through 6 years, DS; and rotary tillage through 2 years followed by deep tillage next year with maize straw applied for two cycles, RS/DS) and three N levels (HN, 300 kg N ha−1, refers to traditional farming practice; MN, 0.75 × HN, 225 kg N ha−1, to recommended N rate; and LN, 0.5 × HN, 150 kg N ha−1, to reduced N rate) were tested. The soil organic carbon, labile organic carbon, inorganic N, available phosphorus, and available potassium under straw return treatments were significantly higher than RT in the 0–30 cm soil layer (p < 0.05). The microbial diversity, invertase, urease, and alkaline phosphatase activities also increased when maize straw was returned. Tillage practices could distribute maize straw in different depths of the soil and then affect soil nutrients, enzyme activity, and microbial diversity. The RS treatment presented the greatest effects in the 0–10 cm layer, while more significant impacts were observed in DS and RS/DS treatments at the 10–30 cm depths. The levels of soil nutrients and enzyme activity increased with an increased N rate. Compared to that under LN, wheat yields increased under HN and MN treatments, whereas there were no significant differences between HN and MN (p > 0.05). An increasing tendency of grain yield was observed in DS and RS/DS, while conversely so in RS. RS/DS had lower farm costs than DS during the study duration. Thus, RS/DS at 225 kg N ha−1 is the best method for improving soil fertility and wheat yield.

Promotive Role of 5-Aminolevulinic Acid or Salicylic Acid Combined with Citric Acid on Sunflower Growth by Regulating Manganese Absorption

Manganese (Mn) is an essential nutrient in most organisms. Establishing an effective regulatory system of Mn absorption is important for sustainable crop development. In this study, we selected sunflower as the model plant to explore the effects of 5-aminolevulinic acid (ALA) or salicylic acid (SA) combined with citric acid (CA) on Mn absorption. Six-leaf-old sunflower plants were exposed to 0.8 g kg-1 Mn for one week and then treated with chelating agents, i.e., CA (10 mmol kg-1), and different concentrations of ALA and SA for one week. The results showed that Mn-treated plants had significantly increased H2O2, O2- and MDA contents in leaves compared with the control. Under the Mn + CA treatment, ALA or SA2 significantly activated the antioxidant defense system by increasing SOD, POD and CAT activities in leaves. Moreover, the application of CA significantly increased the Mn uptake in sunflower roots compared with Mn treatment alone; however, did not accelerate the translocation efficiency of Mn from sunflower roots to shoots. Moreover, ultrastructural and RT-qPCR results further demonstrated that ALA/SA could recover the adverse impact of excessive Mn accumulation in sunflowers. Like a pump, ALA/SA regulated the translocation efficiency and promoted the transportation of Mn from roots to shoots. This study provides insights into the promotive role of ALA/SA combined with CA on sunflower growth by regulating Mn absorption, which would be beneficial for regulating Mn absorption in soil with an Mn deficit.

Possible Involvement of Cellular Pathway and Cytokines in Manganese Induced Neurotoxicity in Neuroblastoma Cells via KH–Type Splicing Regulatory Protein

Pharmacognosy Research,2023,15,2,307-314.DOI:10.5530/pres.15.2.033Published:February 2023Type:Original Article Authors:Sharad Singh, Sunil More, G. S. Latha, Himanshu Agrawal, Veena S M, and Francois Niyonzima Author(s) affiliations:Sharad Singh1, Sunil More1,*, G. S. Latha2, Himanshu Agrawal3, Veena S M4, Francois Niyonzima5 1School of Basic and Applied Sciences, Dayananada Sagar University, Bangalore, Karnataka, INDIA. 2Department of Physiology, Rajarajeswari Medical College and Hospital, Bengaluru, Karnataka, A Constituent College under Dr. M.G.R. Educational and Research Institute, Chennai, Tamil Nadu, INDIA. 3Jubilant Biosys Limited, Bangalore, Karnataka, INDIA. 4Department of Biotechnology, Sapthagiri College of Engineering, Bengaluru, Karnataka, INDIA. 5Department of Mathematics, Sciences and Physical Education, University of Rwanda-College of Education (UR-CE), Kayonza Rukara Campus, RWANDA. Abstract:Background: Manganese is a toxic essential trace element and too high concentration instigates the neurodegenerative disease known as parkinsonism. Effects of manganese may lead to apoptosis. However, a detailed mechanism of manganese toxicity has not been fully elucidated. Previous published articles have highlighted the augmentation of KHSRP expression following Mn exposure. Objectives: In this work, the importance of KHSRP in Mn–induced toxicity was checked along with the impact of other known neurotoxicity inhibitors on KHSRP. Materials and Methods: KHSRP expression, pro and anti-inflammatory cytokines, chemokines, and pharmacological inhibitors (SAHA, Quercetin, and MCC950) were determined by exposing N2a cells to various MnCl2 concentrations. ANOVA and Dunnett’s test were used to decide on the significance. Results: MnCl2 treatment led to the augmentation of the KHSPR mRNA expression and protein increase in N2a cell line. The MnCl2 treatment of N2a cells also showed an elevated liberation of IL-6, TNF-α, MCP–1, and IL-1β. Pharmacological agents like quercetin inhibiting PI3K, MAPK, and WNT pathways, MCC950 blocking NLRP3 pathways, and SAHA showed a decrease in KHSRP expression post Mn treatment. With the inhibition of KHSRP, a decline in the release of IL-1β, IL-6, MCP–1, and TNF-α was also observed. Conclusion: These results suggested that MnCl2 treatment of N2a cells induce the expression of KHSRP via the PI3K–or NLRP3 pathway. Furthermore, this elevated expression of KHSRP is responsible for an increment in the liberation of pro-inflammatory markers in N2a cells. More exploration is needed to throw light on the pathway driving the KHSRP. Keywords:KH–type Splicing Regulatory Protein, Manganese Neurotoxicity, Neuroblastoma, Neurodegeneration, Neuroinflammation.View:PDF (1.26 MB)

EGCG alleviated Mn exposure-caused carp kidney damage via trpm2-NLRP3-TNF-α-JNK pathway: Oxidative stress, inflammation, and tight junction dysfunction

Manganese (Mn), an essential trace metal element in organisms. However, with extensive use of Mn in industry and agriculture, Mn becomes a heavy metal pollutant in water. (−)-epigallocatechin gallate (EGCG), an tea polyphenols, can alleviate metal toxicity. Kidney is an important detoxifying organ, but toxic mechanism of Mn to kidneys is unclear, which needs further research. Carp is an Asian important economical species for fisheries and a biological model for studying environmental toxicology. Thus, we established excess Mn and EGCG-supplemented carp model to explore molecular mechanism of EGCG alleviating Mn-caused carp kidney damage. In this experiment, we set a control group (the Con group), a Mn treatment group (the Mn group, 90 mg/L Mn), a EGCG supplement group (the EG group, 75 mg/kg EGCG), and a combined group (the Mn + EG group, 90 mg/L Mn and 75 mg/kg EGCG). Transcriptome, qRT-PCR, kit, and morphology method results indicated that excess Mn caused oxidative stress, inflammatory damage, and tight junction dysfunction in carp kidneys. Excess Mn-triggered oxidative stress caused tight junction dysfunction via trpm2-NLRP3-TNF-α-JNK pathway and inflammation. EGCG reversed the harm of Mn to fish through the above mechanism. The findings of this study provided the evidence of EGCG-alleviated Mn poisoning and offered new ideas for reducing heavy metal environmental pollution risk.

The comparative effects of manganese nanoparticles and their counterparts (bulk and ionic) in Artemisia annua plants via seed priming and foliar application.

The world has experienced an unprecedented boom in nanotechnology. Nanoparticles (NPs) are likely to act as biostimulants in various plants due to having high surface/volume value. However, understanding the actual effect of NPs is essential to discriminate them from other counterparts in terms of being applicable, safe and cost-effective. This study aimed to assay the impact of manganese(III) oxide (Mn2O3)-NPs via seed-priming (SP) and a combination of SP and foliar application (SP+F) on Artemisia. annua performance at several times intervals and comparison with other available manganese (Mn) forms. Our findings indicate that SP with MnSO4 and Mn2O3-NPs stimulates the processes that occur prior to germination and thus reduces the time for radicle emergence. In both applications (i.e., SP and +F), none of the Mn treatments did show adverse phytotoxic on A. annua growth at morpho-physio and biochemical levels except for Mn2O3, which delayed germination and further plant growth, subsequently. Besides, from physio-biochemical data, it can be inferred that the general mechanism mode of action of Mn is mainly attributed to induce the photosynthetic processes, stimulate the superoxide dismutase (SOD) activity, and up-regulation of proline and phenolic compounds. Therefore, our results showed that both enzymatic and non-enzymatic antioxidants could be influenced by the application of Mn treatments in a type-dependent manner. In general, this study revealed that Mn2O3-NPs at the tested condition could be used as biostimulants to improve germination, seedling development and further plant growth. However, they are not as effective as MnSO4 treatments. Nonetheless, these findings can be used to consider and develop Mn2O3-NPs priming in future studies to improve seed germination and seedling quality in plants.

Protective effect of manganese treatment on insulin resistance in HepG2 hepatocytes.

manganese (Mn) is closely related to type 2 diabetes mellitus and insulin resistance (IR), but the exact mechanism is unclear. This study aimed to explore the regulatory effects and mechanism of Mn on IR using hepatocyte IR model induced by high palmitate (PA), high glucose (HG) or insulin. HepG2 cells were exposed to PA (200 μM), HG (25 mM) or insulin (100 nM) respectively, alone or with 5 μM Mn for 24 hours. The expression of key proteins in insulin signaling pathway, intracellular glycogen content and glucose accumulation, reactive oxygen species (ROS) level and Mn superoxide dismutase (MnSOD) activity were detected. compared with control group, the expression of phosphorylated protein kinase B (Akt), glycogen synthase kinase-3β (GSK-3β) and forkhead box O1 (FOXO1) in the three IR groups was declined, and this decrease was reversed by Mn. The reduction of intracellular glycogen content and increase in glucose accumulation in IR groups were also inhibited by Mn. Additionally, the production of ROS was increased in IR models, compared with normal control group, while Mn reduced the excessive production of ROS induced by PA, HG or insulin. However, Mn did not alter the activity of MnSOD in the three IR models. this study demonstrated that Mn treatment can improve IR in hepatocytes. The mechanism is probably by reducing the level of intracellular oxidative stress, enhancing the activity of Akt/GSK-3β/FOXO1 signal pathway, promoting glycogen synthesis, and inhibiting gluconeogenesis.

PENGARUH Mangan (Mn) TERHADAP OKSIDASI KROMIUM TRIVALEN DAN PERTUMBUHAN Tagetes sp.

Chromium can be found in 2 oxidation states, trivalent chromium (Cr3+) and hexavalent chromium (Cr6+) in environment. Trivalent chromium can be oxidized by manganese oxide to hexavalent chromium (Cr6+). The aim of the study was to determine the effect of Mn on the oxidation of Cr³⁺and plant growth of Tagetes. The study was conducted experimentally using a completely randomized design. The Tagetes plants grown in media with 2 treatment factors, namely Cr3+ (CrCl3) with 3 concentrations of 0, 100 and 500 mg/l) and Mn (MnSO4) with 4 concentrations of 0, 1, 5 and 10 mg/l. The plant growth and Cr6+ content in roots and shoots were measured to determine the effect and to detect the occurrence of Cr3+ oxidation. The addition of Mn in the media of Tagetes containing Cr3+ increased the Cr3+ oxidation process, indicated by the detection of Cr6+ in the roots and shoots of Tagetes. The highest Cr6+ content was found in the roots and shoots of Tagetes sp. treated with Cr3+ 500 mg/l and Mn 10 mg/l at 0.059 and 0.035 g/l, respectively. The interaction of Cr3+ and Mn treatments significantly affected the growth of Tagetes plants. Cr3+ and Mn at high concentrations increased plant height, root length, root and shoot dry weight. The interaction of Cr3+ and Mn at high concentrations inhibited the increase in the number of leaves of Tagetes.

Long-Term Manure Amendment Sustains Black Soil Biodiversity by Mitigating Acidification Induced by Chemical N Fertilization.

The long-term use of chemical N fertilization may have a negative impact upon soil fertility and quality. On the contrary, organic fertilization is considered a sustainable development agricultural strategy. However, the remediation effect of organic fertilization on agroecosystems remains unclear. This study was conducted in a long-term (1979-2020) field experiment to investigate the influence of organic and chemical fertilizers on the soil microbiome assembly processes. The experiment consisted of six treatments: chemical N fertilization (N), double N fertilization (N2), organic fertilization (M), organic and N fertilization (MN), double organic and N fertilization (M2N2), and unfertilized control. The chemical N fertilization (N and N2) treatments significantly decreased soil microbial diversity, as well as soil pH, compared to the Control treatments (p < 0.05). MN and M2N2 treatments increased microbial diversity compared to that of N and N2 treatments. The combination of organic and chemical N fertilizer recovered the decreased microbial diversity to the level of the Control and M treatments, but the application of double organic fertilizer (M2N2) still showed a significantly lower microbial diversity than that of the Control and M treatments. From the results of the microbial community assembly processes, it was found that environmental filtering was induced by N fertilization, while organic fertilization developed a stochastic process and mitigated the role of environmental filtering in the community assembly process. An ecological network analysis showed that the decrease in Acidobacteria in organic fertilization treatments played a key role in mitigating the soil acidification induced by 40-year chemical N fertilization. It indicated that organic fertilizer could mitigate the decrease in soil fertility induced by chemical N fertilization. Higher environmental filtering effects in M2N2 than those in MN treatments suggested that the mitigation effect of organic fertilizer was weakened when double chemical N fertilization was applied in black soils. These results are helpful for a unified understanding of the ecological processes for microbial communities in the development of sustainable agriculture.

ABNO-Functionalized Silica as an Efficient Catalyst for Enhancing Permanganate Oxidation of Emerging Contaminants.

Recent reports indicate that some soluble electron-shuttling compounds (or organic mediators) can accelerate reactions between permanganate (Mn(VII)) and contaminants of emerging concern. However, practical application is limited to homogeneous electron-shuttling compounds. This study reports on the development and application of a heterogeneous electron-shuttling catalyst for Mn(VII) reactions with bisphenol A (BPA). First, we screened a series of poly/monocyclic nitroxides, finding that 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO) provides the most significant enhancement of Mn(VII)/BPA reaction kinetics, where Mn(VII) oxidizes ABNO to BPA-reactive ABNO+. Next, we immobilized ABNO onto silica (SiO2) by covalent bonding of 9-azabicyclo[3,3,1]nonan-3-one-9-oxyl (keto-ABNO) via a 3-aminopropyltriethoxysilane bridge to yield an ABNO@SiO2 heterogeneous catalyst. The performance of ABNO@SiO2 in catalyzing Mn(VII)/BPA reactions is demonstrated, with BPA reaction kinetics being highly dependent on catalyst dosage and pH conditions. The stability of ABNO@SiO2 was retained at pH 5.0 and decreased slightly at pH 7.0 over five successive Mn(VII)/BPA reaction cycles. Kinetics modeling shows that BPA reacts with immobilized ABNO+, Mn(VII), and in situ formed MnO2. Moreover, ABNO+ can form via ABNO reactions with both Mn(VII) and the in situ formed MnO2. These results indicate a promising strategy for developing practical heterogeneous catalysts for enhancing Mn(VII) reactivity and treatment applications.

Impacts of Long-Term Micronutrient Fertilizer Application on Soil Properties and Micronutrient Availability

Deficiencies of micronutrients in calcareous soils have been reported in different areas of China's Loess Plateau. The objective of this research was to study the influence of the continuous application of micronutrient fertilizers on soil properties and micronutrient availability in this region. The micronutrient fertilizer field plot experiment began in 1984. It included Zn, Mn and Cu fertilizer treatments and the control treatment. The crop system was continuously cropped winter wheat. The soil properties and available Zn, Mn, Cu and Fe were measured. Their relationships were analyzed through correlation and path analysis. After 31 years, the soil pH, CaCO3 and available P levels decreased; in contrast, the organic matter, fulvic acid, reducing substances and soil moisture levels in the surface soil increased in the micronutrient fertilized treatments compared to the control treatment. Cu and Zn fertilizers promoted the available Cu and Zn levels in the surface and deep soil, but available Mn was not significantly affected by Mn fertilizer. It can be seen from the interaction between the micronutrient availability and micronutrient fertilizers that Zn, Cu and Mn fertilizers can increase the available Fe level; Mn fertilizer can increase the available Cu level, and Cu and Mn fertilizers can increase the available Zn level. This means that Fe, Cu and Zn availability were easy to implement, whereas the soil-available Mn was difficult to improve in calcareous soils on the Loess Plateau. Fulvic acid and organic matter showed a significant and direct effect on the available Zn; the available Mn and Fe were mainly affected by the soil CaCO3 and moisture; the available Cu was mainly affected by the soil organic matter, available P and reducing substances. These results indicate the importance of organic matter in calcareous soils; it can not only directly affect the availability of micronutrients but also indirectly affect their availability through the indirect interaction with fulvic acid, reducing substances, available P and CaCO3. The above conclusions suggest that the long-term micronutrient fertilizers changed some important soil properties and increased the micronutrient availability in the loess-derived soil.

Reprisal of Schima superba to Mn stress and exploration of its defense mechanism through transcriptomic analysis.

One of the most diverse protein families, ATP-binding cassette (ABC) transporters, play a role in disease resistance, heavy metal tolerance, and food absorption.Differentially expressed genes contribute in the investigation of plant defense mechanisms under varying stress conditions. To elucidate the molecular mechanisms involved in Mn metal stress, we performed a transcriptomic analysis to explore the differential gene expression in Schima superba with the comparison of control. A total of 79.84 G clean data was generated and 6558 DEGs were identified in response to Mn metal stress. Differentially expressed genes were found to be involved in defense, signaling pathways, oxidative burst, transcription factors and stress responses. Genes important in metal transport were more expressive in Mn stress than control plants. The investigation of cis-acting regions in the ABC family indicated that these genes might be targeted by a large variety of trans-acting elements to control a variety of stress circumstances. Moreover, genes involved in defense responses, the mitogen-activated protein kinase (MAPK) signaling and signal transduction in S. superba were highly induced in Mn stress. Twenty ABC transporters were variably expressed on 1st, 5th, and 10th day of Mn treatment, according to the qRT PCR data. Inclusively, our findings provide an indispensable foundation for an advanced understanding of the metal resistance mechanisms. Our study will enrich the sequence information of S. superba in a public database and would provide a new understanding of the molecular mechanisms of heavy metal tolerance and detoxification.

Maize diversification and nitrogen fertilization effects on soil nitrous oxide emissions in irrigated mediterranean conditions

Maize is a major irrigated crop in Mediterranean areas and its typical intensive management may impact soil nitrous oxide (N2O) emissions. In these irrigated continuous maize systems, the legumes incorporation as well as adjusted nitrogen (N) fertilization might be interesting strategies to reduce soil N2O emissions. The objective of this study was to assess the impact of cropping diversification and different N rates on soil N2O emissions in flooded irrigated maize under Mediterranean conditions. To achieve this, two cropping systems (maize monoculture system, MC; and pea -maize rotation, MP) and 3N rates (unfertilized, 0N; medium rate, MN; and high rate, HN) were evaluated in a field experiment established in NE Spain during 2 years (2019; 2020). During the studied period, the N rate had a significant effect on soil N2O emissions, with a non-linear positive response of cumulative soil N2O emissions to N rates. In both systems, quick and high increases of soil N2O fluxes were observed immediately after the N application reaching 55 and 100 mg N2O-N m−2 day−1 in MC and MP, respectively. Both years, the pea phase of the MP rotation showed greater cumulative N2O emissions than the fallow of MC. However, N2O losses in the maize phase were similar (2019) or even higher (2020) in MC than in MP. Moreover, in both seasons, the MN treatments showed lower yield-scaled N2O emissions and N emission factor than the HN treatments, being this last lower than 1% in all cases. The results obtained showed that in irrigated Mediterranean conditions the replacement of a fallow by a legume, together with an adjusted N fertilization are favourable strategies to mitigate soil N2O emissions in high-yielding maize systems.

Resveratrol Attenuated Manganese-Induced Learning and Memory Impairments in Mice Through PGC-1Alpha-Mediated Autophagy and Microglial M1/M2 Polarization.

Overexposure to manganese (Mn) can induce cognitive deficits, but the underlying mechanisms are unclear. Microglial dysfunction and autophagic dysfunction have been implicated in Mn neurotoxicity. The neuroprotective effects of resveratrol (RSV) have been studied extensively, but the potential protective effects of RSV against Mn-induced cognitive dysfunction have not been evaluated. We investigated the effects of RSV on Mn-induced changes in PGC-1α, microglial M1/M2 polarization, and autophagy in vivo and in vitro. Kunming mice were treated with saline, MnCl2, RSV, or MnCl2 + RSV. The results showed that RSV improved cognitive dysfunction, suppressed release of inflammatory cytokines, promoted M2 microglial polarization, and increased autophagy in the hippocampi of Mn-treated mice. Furthermore, we also showed that Mn treatment significantly decreased the expression of PGC-1α, ULK1, BDNF, and activated NF-κB signaling. These effects were reversed by RSV pretreatment. In addition, RSV inhibited STAT6 acetylation, but did not affect ULK1 acetylation. Knockdown of PGC-1α using LV-PGC-1α shRNA reversed RSV-induced increases in the expression levels of PGC-1α, ULK1, LC3-II, and mitigated the RSV-induced decrease in the expression level of p62, in Mn-treated BV2 cells. Resveratrol-induced M2 polarization and autophagic flux were abolished by LV-PGC-1α shRNA pretreatment. These results showed that RSV exerted neuroprotective effects against Mn-induced learning and memory impairment partially through PGC-1α-mediated microglial M1/M2 polarization and autophagy.

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.

Manganese toxicity-induced chlorosis in sugarcane seedlings involves inhibition of chlorophyll biosynthesis

Manganese (Mn) toxicity-induced leaf chlorosis limits crop production in acidic soils, but its underlying mechanisms remain unknown. The effects of excessive Mn on chlorophyll (Chl) biosynthesis in sugarcane (Saccharum officinarum L.) leaves were investigated. Under Mn treatment, Chl concentration decreased with Mn accumulation and chlorosis appeared in expanding leaves. Before that, levels of the initial Chl precursor 5-aminolevulinic acid (ALA) and its downstream intermediates decreased, whereas magnesium-protoporphyrin IX monomethyl ester (MgPME) accumulated. Overaccumulation of Mn in leaves downregulated the ALA biosynthetic gene GluTR (encoding glutamyl-tRNA reductase) and MgPME conversion gene MgPMEC (encoding MgPME cyclase), upregulated the ALA biosynthesis inhibitor FLU (encoding FLUORESCENT), but had no significant effect on the expression of other Chl biosynthetic genes. The above Mn-induced changes of Chl precursors and expression of corresponding genes commenced before the Chl decline and leaf chlorosis, and were reversed by ALA supplementation. Thus, excessive Mn-induced chlorosis in sugarcane is mediated by a Chl-biosynthesis disorder resulting from the inhibition of ALA synthesis and MgPME conversion.

Mitochondrion Participated in Effect Mechanism of Manganese Poisoning on Heat Shock Protein and Ultrastructure of Testes in Chickens.

Manganese (Mn) poisoning can happen in the case of environmental pollution and occupational exposure. However, the underlying mechanisms of Mn-induced teste toxicity and whether mitochondrion and heat shock proteins (HSPs) are involved in toxic effect of Mn on chicken testes remain poorly understood. To investigate this, MnCl2·4H2O was administered in the diet (600, 900, and 1800mg/kg Mn) of chickens for 30, 60, and 90days. Electron microscopy and qPCR were performed. Results showed that Mn exposure suppressed dose- and time-dependently HSP40 and HSP60 mRNA levels, meanwhile increased does-dependently HSP27, HSP70, and HSP90 mRNA levels at all three time points under three Mn exposure concentrations. Furthermore, Mn treatment damaged myoid cells, spermatocytes, and Sertoli cells through electron microscopic observation, indicating that Mn treatment damaged chicken testes. In addition, abnormal shapes of mitochondria were found, and mitochondria displayed extensive vacuolation. The increase of HSP90 and HSP70 induced by Mn exposure inhibited HSP40 and stimulated HSP27, respectively, in chicken testes, which needs further to be explored. Taken together, our study suggested that there was toxic effect in excess Mn on chickens, and HSPs and mitochondria were involved in the mechanism of dose-dependent injury caused by Mn in chicken testes. This study provided new insights for Mn toxicity identification in animal husbandry production practice.

D-Ribose-LCysteine attenuates manganese-induced cognitive and motor deficit, oxidative damage, and reactive microglia activation

Due to overexposure, manganese (Mn) accumulation in the brain can trigger the inhibition of glutathione synthesis and lead to increased generation of reactive oxygen species (ROS) and oxidative stress. D-Ribose-L-Cysteine (RibCys) has been demonstrated to effectively support glutathione synthesis to scavenge ROS and protect cells from oxidative damage. In the present study, we examined the effects of RibCys on weight changes, cognitive and motor associated activities, oxidative stress markers, striatal and cortical histology, and microglia activation following Mn exposure. Rats were exposed to either saline, Mn or/and RibCys for two weeks. The Mn exposed rats received RibCys either as pre-, co-, or post-treatments. Mn caused a significant decrease in weight, memory and motor activities, increased lactate dehydrogenase level, overexpression of IBA1 reflecting microglia activation, and distortion of the neuronal cytoarchitecture of the striatum and motor cortex, respectively. Interventions with RibCys mitigated Mn-induced neurotoxic events. Our novel study demonstrates that RibCys effectively ameliorates the neurotoxicity following Mn treatment and maybe a therapeutic strategy against the neurological consequences of Mn overexposurec

Impacts of Mn, Fe, and Oxidative Stressors on MnSOD Activation by AtMTM1 and AtMTM2 in Arabidopsis.

It has been reported that the mitochondrial carrier family proteins of AtMTM1 and AtMTM2 are necessary for manganese superoxide dismutase (MnSOD) activation in Arabidopsis, and are responsive to methyl viologen (MV)-induced oxidative stress. In this study, we showed that MnSOD activity was enhanced specifically by Mn treatments. By using AtMnSOD-overexpressing and AtMnSOD-knockdown mutant plants treated with the widely used oxidative stressors including MV, NaCl, H2O2, and tert-butyl hydroperoxide (t-BH), we revealed that Arabidopsis MnSOD was crucial for root-growth control and superoxide scavenging ability. In addition, it has been reported that E. coli MnSOD activity is inhibited by Fe and that MTM1-mutated yeast cells exhibit elevated Fe content and decreased MnSOD activity, which can be restored by the Fe2+-specific chelator, bathophenanthroline disulfonate (BPS). However, we showed that BPS inhibited MnSOD activity in AtMTM1 and AtMTM2 single- and double-mutant protoplasts, implying that altered Fe homeostasis affected MnSOD activation through AtMTM1 and AtMTM2. Notably, we used inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis to reveal an abnormal Fe/Mn ratio in the roots and shoots of AtMTM1 and AtMTM2 mutants under MV stress, indicating the importance of AtMTM1 in roots and AtMTM2 in shoots for maintaining Fe/Mn balance.

Responses of photosynthesis and antioxidant activities in Koelreuteria paniculata young plants exposed to manganese stress

In the current study, a hydroponic test was conducted to investigate the response of Koelreuteria paniculata to different concentrations of Mn in terms of photosynthetic and antioxidant enzyme activities. The results showed that Mn stress decreased plant biomass and the chlorophyll content. The reductions in dry weight were directly attributed to the adversely altered photosynthesis related processes caused by Mn stress in the leaves. The reduction in net photosynthetic rates was mainly caused by the inhibition of biochemical activities, including a decrease of gs, Vcmax, and Jmax, but increasing Ci in the plants. The maximum quantum efficiency of PSII photochemistry (Fv/Fm) and electron transport rate (ETR) declined as Mn concentration increased. In addition, the quantum distribution of PSII was altered by Mn. Mn treatments significantly enhanced malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD), and catalase activity (CAT) and ascorbate peroxidase (APX) activities and then decreased in the tested plants, indicating that the antioxidant system could relieve the oxidative stress under slight and moderate Mn stress, but the system was damaged by severe Mn stress.

Manganese-induced hyperactivity and dopaminergic dysfunction depend on age, sex and YAC128 genotype

Manganese (Mn) is an essential micronutrient but is neurotoxic in excess. Environmental and genetic factors influence vulnerability to Mn toxicity, including sex, age, and the autosomal dominant mutation that causes Huntington disease (HD). To better understand the differential effects of Mn in wild-type (WT) versus YAC128 mice, we examined impacts of Mn exposure across different ages and sexes on disease-relevant behavioral tasks and dopamine dynamics. Young (3-week) and aged (12-month) WT and YAC128 mice received control (70 ppm) or high (2400 ppm) Mn diet for 8 weeks followed by a battery of behavioral tasks. In young female WT mice, high Mn diet induced hyperactivity across two independent behavioral tasks. Changes in the expression of tyrosine hydroxylase (TH) were consistent with the behavioral data in young females such that elevated TH in YAC128 on control diet was decreased by high Mn diet. Aged YAC128 mice showed the expected disease-relevant behavioral impairments in females and decreased TH expression, but we observed no significant effects of Mn diet in either genotype of the aged group. Fast-scan cyclic voltammetry recorded dopamine release and clearance in the nucleus accumbens of eight-month-old WT and YAC128 mice following acute Mn exposure (3×/1 week subcutaneous injections of 50 mg/kg MnCl[2]-tetrahydrate or saline). In WT mice, Mn exposure led to faster dopamine clearance that resembled saline treated YAC128 mice. Mn treatment increased dopamine release only in YAC128 mice, possibly indirectly correcting the faster dopamine clearance observed in saline treated YAC128 mice. The same exposure paradigm led to decreased dopamine and serotonin and metabolites (3-MT, HVA and 5-HIAA) in striatum and increased glutamate in YAC128 mice but not WT mice. These studies confirm an adverse effect of Mn in young, female WT animals and support a role for Mn exposure in stabilizing dopaminergic dysfunction and motivated behavior in early HD.