Molybdenum Transport Research Articles

The role of CO2 in the genesis of Dabie-type porphyry molybdenum deposits

Porphyry-type molybdenum deposits, many of which are in China, supply most of the World’s molybdenum. Of particular importance are the molybdenum deposits located in the Qinling-Dabie region that are responsible for more than half of China’s molybdenum production. A feature that distinguishes this suite of deposits from the better-known Climax and Endako sub-types of porphyry molybdenum deposits is their formation from CO2-rich magmatic-hydrothermal fluids. The role of CO2, if any, in the transport of molybdenum by these fluids, however, is poorly understood. We conducted experiments on the partitioning of molybdenum between H2O-CO2, H2O-NaCl, and H2O-NaCl-CO2 fluids and a felsic melt at 850 °C and 100 and 200 MPa. Here we show that the exsolution of separate (immiscible) brine and vapor leads to the very high brine DMo values needed for efficient extraction of Mo from the magmas forming Dabie-type porphyry molybdenum deposits.

Differential accumulation of metals in the lacustrine and fluvial Alpine bullheads (Cottus poecilopus) and recovery of fish from metal contamination after a flash flood

The spatiotemporal distribution and transport of mercury, zinc, molybdenum, rubidium, and strontium from alpine terrestrial ecosystems to alpine lake and mountain stream populations of Cottus poecilopus were investigated. Metals were measured for 66 wild fish collected from different lakes and Javorinka stream across. Mercury was measured in the pectoral fins, other elements in the skull. Bullheads contained more metals in the alpine lakes than in the mountain stream. In particular, mercury and zinc concentrations in lake bullheads were 6 and 2.5 times higher, respectively, than those of stream-dwelling fish. New data were generated on metal bioaccumulation in fish of understudied West Carpathian alpine lake environments. In July 2018, a major flood occurred in the area of the Javorinka. Already then, the mercury content in bullheads increased significantly. Bioaccumulation of mercury in fish occurred very quickly after the flood and was also significant in the following 2019. Then, the concentrations of mercury quickly decreased up to 70% in 2021–2022. Average concentrations of molybdenum and rubidium in bullheads in the stream rapidly declined in the year following the flood disturbance, but within less than 2 years, the metal levels stabilized at about the same level as in 2017 prior the flood. Strontium concentrations in fish dropped rapidly immediately after the flood, increased in the following years, and dropped again after 4 years, suggesting that many more factors are influencing strontium bioaccumulation in fish that are comparable in magnitude to the flood. The most serious warning seems to be the absence of biogenic zinc. The average concentration in the Alpine bullheads population in the stream has declined by 70% in less than 5 years and is steadily declining. An important result of this study is the demonstration that disturbance by a single factor (heavy rainfall and flooding) has a clear and timely effect on average metal concentrations in the fish population.Graphical abstract

Adaptation to coastal soils through pleiotropic boosting of ion and stress hormone concentrations in wild Arabidopsis thaliana.

Local adaptation in coastal areas is driven chiefly by tolerance to salinity stress. To survive high salinity, plants have evolved mechanisms to specifically tolerate sodium. However, the pathways that mediate adaptive changes in these conditions reach well beyond Na+ . Here we perform a high-resolution genetic, ionomic, and functional study of the natural variation in Molybdenum transporter 1 (MOT1) associated with coastal Arabidopsis thaliana accessions. We quantify the fitness benefits of a specific deletion-harbouring allele (MOT1DEL ) present in coastal habitats that is associated with lower transcript expression and molybdenum accumulation. Analysis of the leaf ionome revealed that MOT1DEL plants accumulate more copper (Cu) and less sodium (Na+ ) than plants with the noncoastal MOT1 allele, revealing a complex interdependence in homeostasis of these three elements. Our results indicate that under salinity stress, reduced MOT1 function limits leaf Na+ accumulation through abscisic acid (ABA) signalling. Enhanced ABA biosynthesis requires Cu. This demand is met in Cu deficient coastal soils through MOT1DEL increasing the expression of SPL7 and the copper transport protein COPT6. MOT1DEL is able to deliver a pleiotropic suite of phenotypes that enhance salinity tolerance in coastal soils deficient in Cu. This is achieved by inducing ABA biosynthesis and promoting reduced uptake or better compartmentalization of Na+ , leading to coastal adaptation.

Molybdenum solubility and partitioning in H2O-CO2-NaCl fluids at 600 °C and 200 MPa

The Mo deposits from the Qinling-Dabie area, central China, which are characteristic for a new type of porphyry Mo deposits named the Collision-type, were formed in CO2-rich magmatic-hydrothermal environments. Yet the effects of CO2 on molybdenum transport and precipitation are still poorly known. To fill this gap and provide insight into the formation of Collision-type porphyry Mo deposit, we performed high pressure experiments to systematically quantify the role of CO2 on the solubility of molybdenum-bearing phases. Molybdenite was placed together with a single-phase H2O-CO2-NaCl fluid (8 wt% NaCl Eq.) at 600 °C and 200 MPa. The experiments were buffered by the pyrite-pyrrhotite-magnetite assemblage. At such conditions, combined microthermometric and LA-ICP-MS analysis of synthetic fluid inclusions reveals that the molybdenite solubility in the fluids coexisting with molybdenite decreases slightly (from 87 ± 17 ppm to 38 ± 13 ppm Mo) with increasing CO2 (from XCO2 = 0.10 to 0.25 M fraction). Such a Mo solubility is comparable to that determined in CO2-free fluids (61 ± 14 ppm) with the same salinity. At XCO2 = 0.33, fluid immiscibility is observed and Mo would partition preferentially into the brine phase, with a DMoliq/vap (=CMoliquid/CMovapor) value of 2.9 ± 1.0 (1σ). The evolution of molybdenite solubility with increasing CO2 in the fluid may be explained by changes of the dielectric constant of the solvent. Our results demonstrate that at the studied experimental temperature and pressure, CO2-rich fluids can transport comparable amounts of molybdenum as in H2O-dominated solutions. Combined with existing literature data over a broad range of pressure, temperature, and oxygen fugacity conditions, our data indicate that decreasing temperature and oxygen fugacity facilitate molybdenite precipitation. Albeit the nil-to-negative effect of CO2 on molybdenum solubility, the presence of CO2 would affect significantly fluid saturation of silicate melts. Notably, boiling is expected to occur at higher pressure in the presence of CO2, which may explain the deeper mineralization depth observed for the Collision-type porphyry molybdenum deposit.

Iron Sulfide Enhanced the Dechlorination of Trichloroethene by Dehalococcoides mccartyi Strain 195.

Iron sulfide (FeS) nanoparticles have great potential in environmental remediation. Using the representative species Dehalococcoides mccartyi strain 195 (Dhc 195), the effect of FeS on trichloroethene (TCE) dechlorination was studied with hydrogen and acetate as the electron donor and carbon source, respectively. With the addition of 0.2 mM Fe2+ and S2–, the dechlorination rate of TCE was enhanced from 25.46 ± 1.15 to 37.84 ± 1.89 μmol⋅L–1⋅day–1 by the in situ formed FeS nanoparticles, as revealed through X-ray diffraction. Comparing the tceA gene copy numbers between with FeS and without FeS, real-time polymerase chain reaction (PCR) indicated that the abundance of the tceA gene increased from (2.83 ± 0.13) × 107 to (4.27 ± 0.21) × 108 copies/ml on day 12. The transcriptional activity of key genes involved in the electron transport chain was upregulated after the addition of FeS, including those responsible for the iron–sulfur cluster assembly protein gene (DET1632) and transmembrane transport of iron (DET1503, DET0685), cobalamin (DET0685, DET1139), and molybdenum (DET1161) genes. Meanwhile, the reverse transcription of tceA was increased approximately five times on the 12th day. These upregulations together suggested that the electron transport of D. mccartyi strain 195 was enhanced by FeS for apparent TCE dechlorination. Overall, the present study provided an eco-friendly and effective method to achieve high remediation efficiency for organohalide-polluted groundwater and soil.

Ammonium Cycling and Nitrification Stimulation during Oil Sludge Remediation by Gram-Positive Bacteria Lysinibacillus sphaericus Using Red Wiggler Earthworm Eisenia fetida

The performance of a mixture between L. sphaericus and E. fetida was evaluated for ammonium cycling and nitrifying bacteria stimulation during oil sludge remediation. The addition of E. fetida significantly increased ammonium concentration (p = 0.0218) and total Colony-forming units (CFU) count p = 0.02848). However, oil sludge with worms and L. sphaericus reached lower ammonium concentrations and CFU counts than sludge with worms alone. Sludge inoculated only with L. sphaericus presented higher ammonium concentration than sludge without inoculum, but the bacterial population reached a lower density during the final days. Final DNA and RNA extractions from all treatments amplified for L. sphaericus putative amoA and Gram-negative nitrifying bacteria amoA genes correlated with diminished ammonium concentrations during the final days of the experiment. Final RNA extractions for L. sphaericus amplified for Molybdenum transporter gene suggesting possible nitrogen fixation by L. sphaericus. The addition of Red Wiggler Earthworm to oil sludge remediation systems may provide better conditions for bacterial populations to carry out hydrocarbon degradation. The addition of E. fetida to a L. sphaericus crude oil biodegradation system may improve soil ammonium concentrations and nitrifying activity, and this could be crucial in oil sludge remediation because of bacterial inhibition due to high C:N ratios. The final product of this process may be used for soil enhancement due to its richness in nutrients and beneficial bacterial populations.

The role of sulfur in molybdenum transport in hydrothermal fluids: Insight from in situ synchrotron XAS experiments and molecular dynamics simulations

Knowledge of the identity and thermodynamic properties of aqueous molybdenum (Mo) species at elevated temperatures and pressures is important for understanding the extraction of Mo from source rocks and the formation of hydrothermal deposits. Chlorine and sulfur are two major components in crustal fluids. Several studies have investigated Mo speciation and solubility in chloride-bearing hydrothermal fluids, but little is known about the behaviour of Mo in sulfur-bearing systems. We used in-situ synchrotron X-ray absorption spectroscopy (XAS) measurements and molecular dynamics (MD) simulations to investigate the predominant Mo species in S-bearing (0.04–2 m NaHS) solutions at 30–394 °C (XAS) and 77–300 °C (MD) and 800 bar. The XAS data show that, similar to previous room temperature studies, the S2− ion progressively replaces O2− in molybdate (MoO42−) to form thiomolybdates (MoO4-xSx2−, x = 1, 2, 3, 4) with increasing NaHS concentrations at temperature up to 394 °C. The MD simulations confirm the identity and structure of the thiomolybdate species determined from the XAS experimental data. The speciation calculations based on the formation constants for the thiomolybdate species extrapolated from the room temperature data agree well with the experimental results. This study indicates that thiomolybdate species are likely to be important in transporting Mo in sulfur-bearing hydrothermal fluids with wide pH ranges (e.g., pH 5–9 at 300 °C) under reduced (sulfide stable) conditions in the Earth crust. Current models of Mo transport in hydrothermal ore fluids need to be re-evaluated to take into account the thiomolybdate species.

Unravelling the antibiotic and heavy metal resistome of a chronically polluted soil.

The antibiotic and heavy metal resistome of a chronically polluted soil (3S) obtained from an automobile workshop in Ilorin, Kwara State, Nigeria was deciphered via functional annotation of putative ORFs (open reading frames). Functional annotation of antibiotic and heavy metal resistance genes in 3S metagenome was conducted using the Comprehensive Antibiotic Resistance Database (CARD), Antibiotic Resistance Gene-annotation (ARG-ANNOT) and Antibacterial Biocide and Metal Resistance Gene Database (BacMet). Annotation revealed detection of resistance genes for 15 antibiotic classes with the preponderance of beta lactamases, mobilized colistin resistance determinant (mcr), glycopepetide and tetracycline resistance genes, the OqxBgb and OqxA RND-type multidrug efflux pumps, among others. The dominance of resistance genes for antibiotics effective against members of the Enterobacteriaceae indicate possible contamination with faecal materials. Annotation of heavy metal resistance genes revealed diverse resistance genes responsible for the uptake, transport, detoxification, efflux and regulation of copper, zinc, cadmium, nickel, chromium, cobalt, mercury, arsenic, iron, molybdenum and several others. Majority of the antibiotic and heavy metal resistance genes detected in this study are borne on mobile genetic elements, which facilitate their spread and dissemination in the polluted soil. The presence of the heavy metal resistance genes is strongly believed to play a major role in the proliferation of antibiotic resistance genes. This study has established that soil is a huge repertoire of antibiotic and heavy metal resistome and due to the intricate link between human, animals and the soil environment, it may be a major contributor to the proliferation of multidrug-resistant clinical pathogens.

Kinetic modeling of molybdenum sorption and transport in soils.

In this investigation, batch and column experiments were conducted to investigate the molybdenum (Mo) sorption and transport processes on a neutral-pH soil (Webster loam) and an acidic soil (Mahan sand) in Ca2+ and K+ background solutions. Batch results showed that the adsorption of Mo was strongly non-linear in both soils and amount of Mo sorbed in the acidic soil was larger than the neutral soil. The Freundlich distribution coefficients (Kf) and Langmuir sorption maxima (Smax) in Ca2+ background solution are larger than that in K+ solution, indicating greater Mo sorption in Ca2+ than in K+. Experimental breakthrough curves (BTCs) demonstrated that mobility of Mo was higher at neutral condition than that at acidic condition. A multi-reaction transport model (MRTM) formulation with two kinetic retention reactions (reversible and irreversible) well described Mo transport for Webster soil. However, MRTM model which accounts for equilibrium and kinetic sites is recommended for Mo transport in Mahan soil, reflecting different soil properties. Based on inverse modeling, the sorption forward rate coefficients (k1) obtained from Ca2+ in both soils are larger than that from K+, which consistent with batch experiment. Overall, MRTM model was capable of describing the Mo transport behavior under different geochemical conditions.

Identification of the symbiosis island of Bradyrhizobium paxllaeri LMTR 21T.

The complete symbiosis island (SI) of Bradyrhizobium paxllaeri LMTR 21T, a mutualistic symbiont of the legume Phaseolus lunatus, was identified and analyzed. The SI was 646 kb in size, had lower G+C content than the genome average, and encoded not only nodulation and nitrogen fixation functions but also those for hydrogen uptake, vitamin and phytohormone biosynthesis, molybdenum transport, nonribosomal peptide synthesis, and type III secretion. Additionally, two divergent nodA genes were encoded in the SI.

Transport and retention of Molybdenum(VI) on iron oxide-coated sand: A modified multi reaction model

In this investigation, batch and miscible displacement experiments were performed to investigate the pH-dependent effect on retention and transport of Mo(VI) on iron oxide-coated sand (IOCS). Measured results indicated that Mo(VI) sorption was strongly nonlinear and kinetically controlled, where the amount of Mo(VI) sorbed and its reaction rates increased with decreasing solution pH. Mo(VI) breakthrough curves (BTCs) obtained at varying pHs were asymmetrical in shape and exhibited different degree of tailing, where mobility of Mo(VI) was lowest under acidic condition (pH 4.0) and highest under alkaline condition (pH 7.5). In this study, based on extended Freundlich equation, we proposed a modified multi-reaction model (M-MRM) including a pH term, which was utilized to describe pH-dependent sorption and transport process. From the goodness-of-fit of modeling results, the M-MRM model provided a good prediction for Mo(VI) retention and transport datasets on IOCS. In comparison to numerical surface complexation models (SCMs), the proposed M-MRM is relatively less complex and requires fewer parameters. Moreover, it is simpler to integrate reaction transport equations into kinetic models to simulate non-equilibrium transport behavior. Our work provided a unified kinetic model to describe pH-dependent sorption and transport in IOCS.

Physics affecting heavy impurity migration in tokamaks: Benchmarking test-ion code ASCOT against TEXTOR tracer experiment

Abstract Erosion, transport and deposition of wall impurities are major concerns in future magnetic fusion devices, both from the perspective of the fusion plasma and the machine wall. An extensive study on molybdenum transport and deposition performed in the TEXTOR tokamak yielded a detailed deposition map that is ideal for benchmark deposition studies. A qualitative benchmark is attempted in this article with the ASCOT code. We set up a full 3D model of the TEXTOR tokamak and studied the influence of different physical mechanisms and their strengths on molybdenum deposition patterns on the simulated plasma-facing components: atomic processes, Coulomb collisions, scrape-off layer (SOL) profiles, source distribution, marker starting energy, radial electric field strength, SOL flow and toroidal plasma rotation. The outcome comprises 13 simulations, each with 100,000 markers. The findings are: • Toroidal plasma movement, either within the LCFS or as SOL flow, is negligible. • SOL profile and marker starting energy have modest impact on deposition. • Source distribution has a large impact in combination with radial electric field profiles. • The E ⇀ × B ⇀ drift has the highest impact on the deposition profiles.

Modeling of molybdenum transport and pressure drop increase in fixed bed reactors used for selective oxidation of methanol to formaldehyde using iron molybdate catalysts

A dynamic model was developed for a single reactor tube, in which methanol oxidation to formaldehyde over an iron molybdate/molybdenum oxide catalyst takes place simultaneously with transport of MoO3 from the catalyst through the reactor. A previously developed dynamic 1D mathematical model for a single ring-shaped cylindrical catalyst pellet, in which volatilization of MoO3 takes place, was implemented in the reactor model. Known axial profiles in a pilot scale reactor with respect to MeOH and H2O concentration and temperature were used as input to the model. MeOH forms volatile Mo-species with solid MoO3 in the catalyst pellets, which diffuses to the bulk gas phase and is transported through the reactor, leading to MoO3 depleted pellets. Volatilization of MoO3 from the pellets occur at the inlet of the reactor. As MeOH is oxidized down the reactor, the volatile Mo-species decomposes via the reverse reaction that formed them. Deposition of MoO3 downstream in the reactor decreases the void space between the catalyst pellets leading to increased pressure drop. The hydraulic diameter of the catalyst pellets and the porosity of the deposited MoO3 were fitted to experimental data obtained in a pilot plant unit containing a single reactor tube. Furthermore, the model was used to simulate a tube under industrial conditions for up to two years (feed composition 8.4% MeOH, 4% H2O, 10% O2 in N2, bed length = 100 cm and a temperature of 190–346 °C). Finally, two cases where catalyst pellets with no excess MoO3 or shaped as filled cylinders are used in the initial 21 cm of the catalyst bed were simulated. The simulations show that this significantly decreases the rate at which the pressure drop increases. This model is a first step towards a useful tool to predict MoO3 transport, pressure drop increase and estimation of process life time at varying reaction conditions.

Transport and Retention of Molybdenum(VI) in Soils: Kinetic Modeling

Core Ideas Mo(VI) sorption was kinetically controlled and highly nonlinear in two different soils. Mo(VI) retention mechanism in Windsor sand was different from Webster loam. Rate‐limited processes greatly influenced Mo(VI) transport in soils. Mo(VI) transport was well described using a second‐order model. Understanding the mechanisms and kinetics controlling the retention and transport of molybdenum [Mo(VI)] is a prerequisite in the effort to evaluate environmental risk of groundwater contamination. In this study, kinetic batch and miscible‐displacement experiments were performed to investigate Mo(VI) adsorption–desorption and transport behaviors on a neutral soil (Webster loam) and a slightly acidic soil (Windsor sand). Batch results indicated that adsorption of Mo(VI) was kinetically controlled and highly nonlinear in both soils. The Mo(VI) maximum adsorption and kinetic rate for acidic Windsor sand was much higher than for neutral Webster loam. Mo(VI) breakthrough curves (BTCs) were asymmetrical and exhibited extensive tailing with incomplete recovery in the effluent: these features demonstrate that rate‐limited or non‐equilibrium process influenced Mo(VI) transport behavior. To better understand the controls on the nonlinear kinetic behavior of Mo transport in these soils, a second‐order (SO) model which accounts for equilibrium, reversible, and irreversible retention mechanisms was used to describe Mo(VI) retention and transport in soils. Based on optimized and predictive modeling results, a fully reversible equilibrium‐kinetic SO model successfully described the time‐dependent Mo(VI) sorption for Webster loam. However, for Windsor sand, which exhibited strong affinity and low mobility for Mo(VI), an additional consecutive irreversible reaction phase was necessary to describe Mo(VI) retention and transport with time.

Abundance and taxonomic affiliation of molybdenum transport and utilization genes in Tengchong hot springs, China

The nitrogen, sulfur and carbon cycles all rely on critical microbial transformations that are carried out by enzymes that require molybdenum (Mo) as a cofactor. Despite Mo importance in these biogeochemical cycles, little information exists about microbial Mo utilization in extreme environments where, due to geochemical conditions, bioavailable Mo may be limited. Using metagenomic data from nine hot springs in Tengchong, Yunnan Province, China, which range in temperature from 42°C to 96°C and pH from 2.3 to 9, the effects of pH, temperature and spring geochemistry on the abundance and taxonomic affiliation of genes related to Mo were studied. Dissolved Mo was only detected at sites with circumneutral pH. However, processes and organisms that require Mo were detected at all sites across all temperature and pH gradients. All sites contained xanthine dehydrogenase, formate dehydrogenase, carbon-monoxide dehydrogenase, nitrate reductase, sulfite oxidase and methionine-sulfoxide reductase despite different community compositions. This suggests that different microbial communities, resulting from different physicochemical conditions, may be performing similar metabolic functions. Furthermore, the abundance and taxonomic diversity of Mo-related annotations increased with higher concentrations of Mo. This study shows that despite geochemical conditions that can limit Mo bioavailability, microbes require Mo for a variety of processes.

Medicago truncatula Molybdate Transporter type 1 (MtMOT1.3) is a plasma membrane molybdenum transporter required for nitrogenase activity in root nodules under molybdenum deficiency.

Molybdenum, as a component of the iron-molybdenum cofactor of nitrogenase, is essential for symbiotic nitrogen fixation. This nutrient has to be provided by the host plant through molybdate transporters. Members of the molybdate transporter family Molybdate Transporter type 1 (MOT1) were identified in the model legume Medicago truncatula and their expression in nodules was determined. Yeast toxicity assays, confocal microscopy, and phenotypical characterization of a Transposable Element from Nicotianatabacum (Tnt1) insertional mutant line were carried out in the one M.truncatula MOT1 family member specifically expressed in nodules. Among the five MOT1 members present in the M.truncatula genome, MtMOT1.3 is the only one uniquely expressed in nodules. MtMOT1.3 shows molybdate transport capabilities when expressed in yeast. Immunolocalization studies revealed that MtMOT1.3 is located in the plasma membrane of nodule cells. A mot1.3-1 knockout mutant showed impaired growth concomitant with a reduction of nitrogenase activity. This phenotype was rescued by increasing molybdate concentrations in the nutritive solution, or upon addition of an assimilable nitrogen source. Furthermore, mot1.3-1 plants transformed with a functional copy of MtMOT1.3 showed a wild-type-like phenotype. These data are consistent with a model in which MtMOT1.3 is responsible for introducing molybdate into nodule cells, which is later used to synthesize functional nitrogenase.

Uptake, transport and distribution of molybdenum in two oilseed rape (Brassica napus L.) cultivars under different nitrate/ammonium ratios.

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11. A hydroponic culture experiment was conducted with four nitrate/ammonium (NO3-:NH4+) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917. Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO3-:NH4+ while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO3-:NH4+ ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO3-:NH4+ ratio was more beneficial for L0917. On the contrary, a lower NO3-:NH4+ ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars' leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO3-:NH4+ ratio. This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO3-:NH4+ ratio conditions.

Effects of tungsten on uptake, transport and subcellular distribution of molybdenum in oilseed rape at two different molybdenum levels

Due to the similarities of molybdenum (Mo) with tungsten (W) in the physical structure and chemical properties, studies involving the two elements have mainly examined their competitive relationships. The objectives of this study were to assess the effects of equimolar W on Mo accumulation, transport and subcellular distribution in oilseed rape at two Mo levels with four treatments: Mo1 (1μmol/L Mo, Low Mo), Mo1+W1 (1μmol/L Mo+1μmol/LW, Low Mo with Low W), Mo200 (200μmol/L Mo, High Mo) and Mo200+W200 (200μmol/L Mo+200μmol/L Mo, High Mo with high W). The fresh weight and root growth were inhibited by equimolar W at both low and high Mo levels. The Mo concentration and accumulation in root was increased by equimolar W at the low Mo level, but that in the root and shoot was decreased at the high Mo level. Additionally, equimolar W increased the Mo concentrations of xylem and phloem sap at low Mo level, but decreased that of xylem and increased that of phloem sap at the high Mo level. Furthermore, equimolar W decreased the expression of BnMOT1 in roots and leaves at the low Mo level, and only decreased its expression in leaves at the high Mo level. The expression of BnMOT2 was also decreased in root for equimolar W compared with the low Mo level, but increased compared with high Mo level. Moreover, equimolar W increased the proportion of Mo in cell wall fraction in root and that of soluble fraction in leaves when compared with the low Mo level. The results suggest that cell wall and soluble fractions might be responsible for the adaptation of oilseed rape to W stress.

Diagnostics for molybdenum and tungsten erosion and transport in NSTX-U.

A comprehensive set of spectroscopic diagnostics is planned in the National Spherical Torus Experiment Upgrade to connect measurements of molybdenum and tungsten divertor sources to scrape-off layer (SOL) and core impurity transport, supporting the installation of high-Z plasma facing components which is scheduled to begin with a row of molybdenum tiles. Imaging with narrow-bandpass interference filters and high-resolution spectroscopy will be coupled to estimate divertor impurity influxes. Vacuum ultraviolet and extreme ultraviolet spectrometers will allow connecting high-Z sources to SOL transport and core impurity content. The high-Z diagnostics suite complements the existing measurements for low-Z impurities (carbon and lithium), critical for the characterization of sputtering of high-Z materials.

In silico identification and comparative analysis of molybdenum (Mo) transporter genes in plants

Molybdenum (Mo) is an essential micronutrient element required by plants at trace amounts. Studies of Mo transporters mainly refer to the general characteristics of sulfate transporters because of limited knowledge about these proteins. In this study, we have identified 39 potential Mo transporter-like genes from 17 plant species by homology search. We report that Mo transporter proteins could be characterized with their Sulfate_transp and/or SUL1 protein domain family, 7–10 putative TMDs, basic characteristics, and mainly single exon number. In addition, we have searched the highly conserved residues in identified Mo sequences. These conserved residues could be used as potential motif signatures in identification of Mo transporter sequences. Phylogenetic analysis demonstrated a clear distinction between lower and higher plants in Mo transporter sequences. Despite some structural variations, general topological features of Mo transporters in higher and lower plants are not much divergent among 17 species. Identification of Mo transporter genes/proteins in various plant species, and their comparative analysis will provide valuable theoretical knowledge for future studies of better characterization of Mo transporters.