Metal transport across biomembranes: Emerging models for a distinct chemistry

Transition metals are essential components of important biomolecules, and their homeostasis is central to many life processes. Transmembrane transporters are key elements controlling the distribution of metals in various compartments. However, due to their chemical properties, transition elements require transporters with different structural-functional characteristics from those of alkali and alkali earth ions. Emerging structural information and functional studies have revealed distinctive features of metal transport. Among these are the relevance of multifaceted events involving metal transfer among participating proteins, the importance of coordination geometry at transmembrane transport sites, and the presence of the largely irreversible steps associated with vectorial transport. Here, we discuss how these characteristics shape novel transition metal ion transport models. © 2012 by The American Society for Biochemistry and Molecular Biology, Inc.Fil: Argüello, José M.. Worcester Polytechnic Institute. Departmen Of Chemistry And Biochemistry; Estados UnidosFil: Raimunda, Daniel Cesar. Worcester Polytechnic Institute. Departmen Of Chemistry And Biochemistry; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Gonzalez Guerrero, Manuel. Universidad Politécnica de Madrid; Españ

Iron distribution through the developmental stages of Medicago truncatula nodules.

Paramount to symbiotic nitrogen fixation (SNF) is the synthesis of a number of metalloenzymes that use iron as a critical component of their catalytical core. Since this process is carried out by endosymbiotic rhizobia living in legume root nodules, the mechanisms involved in iron delivery to the rhizobia-containing cells are critical for SNF. In order to gain insight into iron transport to the nodule, we have used synchrotron-based X-ray fluorescence to determine the spatio-temporal distribution of this metal in nodules of the legume Medicago truncatula with hitherto unattained sensitivity and resolution. The data support a model in which iron is released from the vasculature into the apoplast of the infection/differentiation zone of the nodule (zone II). The infected cell subsequently takes up this apoplastic iron and delivers it to the symbiosome and the secretory system to synthesize ferroproteins. Upon senescence, iron is relocated to the vasculature to be reused by the shoot. These observations highlight the important role of yet to be discovered metal transporters in iron compartmentalization in the nodule and in the recovery of an essential and scarce nutrient for flowering and seed production

MtNramp1 mediates iron import in rhizobia-infected Medicago truncatula cells.

Symbiotic nitrogen fixation is a process that requires relatively high quantities of iron provided by the host legume. Using synchrotron-based X-ray fluorescence, we have determined that this iron is released from the vasculature into the apoplast of zone II of M. truncatula nodules. This overlaps with the distribution of MtNramp1, a plasma membrane iron importer. The importance of MtNramp1 in iron transport for nitrogen fixation is indicated by the 60% reduction of nitrogenase activity observed in knock-down lines, most likely due to deficient incorporation of this essential metal cofactor at the necessary levels

MtYSL1: a putative metal transporter involved in Medicago truncatula-Sinorhizobium meliloti symbiotic interaction

Leguminous plants are able to grow under nitrogen-limiting conditions by establishing an endosymbiotic interaction with diazotrophic soil bacteria known as rhizobia. This interaction results in root structures, nodules, where rhizobia are differenciated to bacteroids and symbiotic nitrogen fixation (SNF) occurs (Van de Velde et al., 2006). Key enzymes involved in SNF require metals as cofactor to carry out their catalytic activity such as nitrogenase, leghemoglobin, cytochrome oxidase and superoxide dismutase. Previous results in Medicago truncatula showed that metals have to be provided to the bacteroids by the host legume, being released to the apoplast of zone II (infection/maturation zone) of the nodule (Rodriguez- Haas et al., 2013). It is known that Yellow Stripe-like (YSL) transporters mediate metal trafficking from the root to sink organs, however, no information of the role of these transporters in the context of SNF is available. Medicago truncatula YSL1 is a good candidate to mediate this transport, since it reaches an expression peak in these organs. MtYSL1 was localized around the vascular conducts of nodules and, in the root pericycle. MtYSL1 immunolocalization showed that it was embedded in the plasma membrane of non-infected cells surrounding the vessels. These results suggest a role of MtYSL1 in metal delivery to M. truncatula nodule

MtZIP6 is a novel metal transporter required for symbiotic nitrogen fixation in nodules of Medicago truncatula plants

Symbiotic nitrogen fixation (SNF) carried out by the interaction rhizobia-legumes takes place in legume root nodules. Many of the enzymes involved in SNF are metalloproteins that obtain their metal cofactor from the host plant. Metals reach the nodule through the vasculature, where they are released in the apoplast on the infection/differentiation zone (zone II) of the nodule (Rodriguez-Haas et al., 2013). From there, these oligonutrients have to cross a number of membranes to be used for metalloprotein synthesis (plasma membrane, endoplasmic reticulum, symbiosomes,..). Although several proteins have been suggested to mediate metal transport to the endosymbiotic nitrogen-fixing rhizobia (bacteroids), very little is known about transporters that mediate metal uptake from the apoplast. Recently, we have identified MtNramp1, the first iron transporter to mediate this uptake (Tejada-Jiménez et al., 2015). However, other transporters must mediate zinc, manganese or copper uptake from the nodule apoplast. Transcriptomic studies in Medicago truncatula revealed that MtZIP6, a ZIP family member, had a maximum of expression in the nodule. ZIP6 promoter::GUS fusions showed that MtZIP6 expression was confined to the nodule zone II, the region where metals have to be incorporated from the apoplast. These results were also validated by immunohistochemistry in nodule sections expressing MtZIP6 bound to 3xHA epitopes under the MtZIP6 promoter. This experiment showed that MtZIP6 is very likely localized in the plasma membrane and confirmed its expression in zone II of the nodule. Expression of MtZIP6 in Saccharomyces cerevisiae metal transport mutants showed MtZIP6 as a divalent metal importer, capable of transporting zinc, manganese, or iron. Loss of MtZIP6 function in M. truncatula knocked-down plants revealed a reduced plant and nodule size, and a reduced nitrogenase activity in comparison to control plants. Altogether these results suggest that MtZIP6 is an important element in the process of symbiotic nitrogen fixation by its ability to transport metals through the plasma membrane of the nodule cell

Metal Transport in the Rhizobium-Legume Symbiosis

Metal Transport in the Rhizobium-legume Symbiosi

MtCOPT1 mediates copper transport to Medicago truncatula nodules

Copper is an essential oligonutrient. Its redox properties allow it to be a suitable cofactor for many proteins, such as cytochromes or superoxide dismutases. Copper is key for Symbiotic Nitrogen Fixation (SNF); For instance, bacteroids contain copper-dependent cytochrome oxidases that provide energy in the microaerobic environment within the nodule. Once copper is in the plant, it is delivered by the vasculature to the apoplast of zone II. From there, a plasma membrane transporter introduces this nutrient into the cell for copper-protein assembly. COPT family transporters mediate high-affinity copper transport towards the cytosol. Therefore, they are good candidates to introduce copper in nodule cells. From the 8 COPT family genes present in M. truncatula genome, MtCOPT1 is the only one induced specifically in nodule. MtCOPT1 can restore Saccharomyces cerevisae ?ctr1 capacity to uptake copper. Inmunolocalization and GUS fusion studies localize MtCOPT1 in the nodule. Moreover, a Tnt-1-derived knockdown mutant line for MtCOPT1 shows decreased nitrogenase activity when compared with the wild-type line. This activity is, at least, partially rescued when a wild-type copy of MtCOPT1 gene is reintroduced. Taken together, all this data suggest an important role of MtCOPT1 copper-mediated transport for SNF

MtNramp1 is responsible for iron uptake by rhizobia infected cells in Medicago truncatula nodules

All known organisms need iron to accomplish important biological processes for life, ranging from gene transcription to respiration. Particularly in symbiotic nitrogen fixation (SNF) iron plays a critical role since the activity of key proteins involved in this process, such as nitrogenase, leghemoglobin, Fe-superoxide dismutase and other proteins involved in energy transduction, directly depends on the presence of iron as cofactor in their active centre. In the model legume Medicago truncatula, iron is delivered by the vasculature and released in the apoplast on the zone II of the nodule (infection/maturation zone). Then iron moves into rhizobia-infected cells and it is used in the synthesis of iron-containing proteins. Therefore, different iron transporters should mediate iron traffic through the plasma membrane of plant cells and the symbiosome membrane. However, no candidates were available to be responsible for iron transport across the plasma membrane from the nodule apoplast to rhizobia-infected cells. In the present work, we have identified a Nramp member gene from M. truncatula (MtNramp1) as responsible for iron transport from nodule apoplast into rhizobia-infected cell. MtNramp1 shows the highest expression in the nodule among the seven Nramp genes present in M. truncatula genome. Immunolocalization studies show that MtNramp1 is located in the plasma membrane of zone II nodule cells. A loss-of-function nramp1 mutant presented impaired growth specifically under symbiotic conditions, concomitant with a lower nitrogenase activity compared to wild-type plants. This phenotype was rescued by the addition of iron to the nutritive solution or by complementation of a mutant with a wild-type Nramp1 copy. Furthermore yeast complementation assays using mutant affected on iron transport pointed to a role of MrNramp1 in iron transport toward the cytosol. All together, these results point to a role of MtNramp1 in iron supply to nodule cells connected to SNF, and represent an important step toward the understanding of iron incorporation and homeostasis in plant nitrogen-fixing tissues

IFE Plant Technology Overview and contribution to HiPER proposal

HiPER is the European Project for Laser Fusion that has been able to join 26 institutions and signed under formal government agreement by 6 countries inside the ESFRI Program of the European Union (EU). The project is already extended by EU for two years more (until 2013) after its first preparatory phase from 2008. A large work has been developed in different areas to arrive to a design of repetitive operation of Laser Fusion Reactor, and decisions are envisioned in the next phase of Technology Development or Risk Reduction for Engineering or Power Plant facilities (or both). Chamber design has been very much completed for Engineering phase and starting of preliminary options for Reactor Power Plant have been established and review here

Hollow Gold Nanoparticles Produced by Femtosecond Laser Irradiation

[EN] Metallic hollow nanoparticles exhibit interesting optical properties that can be controlled by geometrical parameters. Irradiation with femtosecond laser pulses has emerged recently as a valuable tool for reshaping and size modification of plasmonic metal nanoparticles, thereby enabling the synthesis of nanostructures with unique morphologies. In this Letter, we use classical molecular dynamics simulations to investigate the solid-to-hollow conversion of gold nanoparticles upon femtosecond laser irradiation. Here, we suggest an efficient method for producing hollow nanoparticles under certain specific conditions, namely that the particles should be heated to a maximum temperature between 2500 and 3500 K, followed by a fast quenching to room temperature, with cooling rates lower than 120 ps. Therefore, we describe the experimental conditions for efficiently producing hollow nanoparticles, opening a broad range of possibilities for applications in key areas, such as energy storage and catalysis.This work has been funded by the Spanish Ministry of Science, Innovation and Universities (MICIU) (Grants RTI2018-095844-B-I00, PGC2018-096444-B-I00, and MAT2017-86659-R), the EUROfusion Consortium through Project ENR-IFE19.CCFE-01, and the Madrid Regional Government (Grants P2018/NMT-4389 and P2018/EMT-4437). A.P. is thankful for the support of FONDECYT under Grants 3190123 and 11180557, as well as from Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia FB-0807. K.L. acknowledges the support of the Russian Science Foundation (Project 19-19-00683). The authors acknowledge the computer resources and technical assistance provided by the Centro de Supercomputacion y Visualizacion de Madrid (CeSViMa) and the supercomputing infrastructure of the NLHPC (ECM-02). This Letter is based upon work from COST Action TUMIEE (CA17126)Castro-Palacio, JC.; Ladutenko, K.; Prada, A.; Gonzalez-Rubio, G.; Diaz-Nunez, P.; Guerrero-Martinez, A.; Fernández De Córdoba, P.... (2020). Hollow Gold Nanoparticles Produced by Femtosecond Laser Irradiation. The Journal of Physical Chemistry Letters. 11(13):5108-5114. https://doi.org/10.1021/acs.jpclett.0c01233S51085114111