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Volker Römheld - One of the best experts on this subject based on the ideXlab platform.

  • Effect of nitrogen on root release of Phytosiderophores and root uptake of Fe(III)-phytosiderophore in Fe-deficient wheat plants.
    Physiologia plantarum, 2011
    Co-Authors: Seher Bahar Aciksoz, Volker Römheld, Levent Ozturk, Ozay Ozgur Gokmen, Ismail Cakmak
    Abstract:

    Root release of Phytosiderophores (PSs) is an important step in iron (Fe) acquisition of grasses, and this adaptive reaction of plants is affected by various plant and environmental factors. The objectives of this study were to study the effects of varied nitrogen (N) supply on (1) root and leaf concentrations of methionine, a precursor in the PS biosynthesis, (2) PS release from roots, (3) mobilization and uptake of Fe from (59) Fe-labeled Fe(III)-hydroxide [(59) Fe(OH)(3) ] and (4) root uptake of (59) Fe-labeled Fe(III)-deoxymugineic acid (DMA) by durum wheat (Triticum durum, cv. Balcali2000) plants grown in a nutrient solution. Enhanced N supply from 0.5 to 6 mM in a nutrient solution significantly increased the root release of PS under Fe deficiency. High N supply was also highly effective in increasing mobilization and root uptake of Fe from (59) Fe-hydroxide under low Fe supply. With adequate Fe, N nutrition did not affect mobilization and uptake of Fe from (59) Fe(OH)(3) . Root uptake and shoot translocation of Fe supplied as (59) Fe(III)-DMA were also stimulated by increasing N supply. Leaf concentration of methionine was reduced by low Fe supply, and this decline was pronounced in high N plants. The results show that the root release of PS, mobilization of Fe from (59) Fe(OH)(3) and root uptake and shoot translocation of Fe(III)-PS by durum wheat are markedly affected by N nutritional status of plants. These positive N effects may have important implications for Fe nutrition of human populations and should be considered in biofortification of food crops with Fe.

  • Uptake and apoplastic retention of EDTA‐ and phytosiderophore‐chelated chromium(III) in maize
    Journal of Plant Nutrition and Soil Science, 2007
    Co-Authors: B. Erenoglu, Volker Römheld, Hicham Khodr, Hemanta Kumar Patra, Nicolaus Von Wirén
    Abstract:

    Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant-borne chelators might be relevant for the design of phytoremediation strategies on Cr-contaminated sites. Short-term uptake studies in maize roots supplied with 51 CrCl 3 or 51 Cr(III)-EDTA led to higher apoplastic Cr contents in plant roots supplied with 51 CrCl 3 and in Fe-sufficient plants relative to Fe-deficient plants, indicating that Fe stimulated co-precipitation of Cr. Concentration-dependent retention of Cr in a methanol:chloroform-treated cell-wall fraction was still saturable and in agreement with the predicted tendency of Cr(lll) to precipitate as Cr(OH) 3 . To investigate a possible stimulation of Cr(lll) uptake by Phytosiderophores, Fe-deficient maize roots were exposed for 6 d to Cr(lll)-EDTA or Cr(lll)-DMA (2'-deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 μM resulted in alleviation of Fe deficiency-induced chlorosis and higher Cr accumulation. Long-term Cr accumulation from Cr(lll)-DMA was similar to that from Cr(lll)-EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal-phytosiderophore uptake. We therefore conclude that Phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr-contaminated sites.

  • Speciation of iron coordinated by Phytosiderophores by use of HPLC with pulsed amperometric detection and AAS.
    Analytical and bioanalytical chemistry, 2002
    Co-Authors: Günther Weber, Günter Neumann, Volker Römheld
    Abstract:

    Phytosiderophores of the mugineic acid family, and the respective iron species, have been separated by anion-exchange chromatography with NaOH gradient elution. Two different detection methods were used in parallel, pulsed amperometry (PAD) for Phytosiderophores and atomic absorption spectrometry (AAS) for iron. This combination enables identification of separated iron species. Up to five different iron species were separated and detected within 30 min – two different phytosiderophore species, two amino acid species, and one species which has not yet been identified but which is most probably a decomposition product of Phytosiderophores. The detection limit was in the low µmol L–1 concentration range, which is sufficiently low for determination in real plant samples, even after dilution. The method has been applied to root washings of iron-deficient wheat and barley plants and to a xylem exudate of non-deficient maize.

  • Role of Phytosiderophores in Zinc Efficiency of Wheat
    Durchwurzelung Rhizodeposition und Pflanzenverfügbarkeit von Nährstoffen und Schwermetallen, 2002
    Co-Authors: Bhupinder Singh, Volker Römheld, B. Erenoglu, Günter Neumann, Nikolaus Von Wirén
    Abstract:

    It is still an open question whether the zinc deficiency-induced release of Phytosiderophores (PS, phytometallophores) significantly contributes to zinc nutrition of graminaceous plant species. The present studies were attempted to compare the production and release of Phytosiderophores by roots of aestivum and durum wheat under Fe and Zn deficiency, since durum wheat showed lower Zn efficiency in field studies relative to aestivum wheat. It was found that phytosiderophore release by roots is induced under Zn deficiency and that durum wheat released significantly lower amounts of PS than aestivum wheat under Zn stress while under Fe stress the difference in release of PS for the two wheat types was much smaller. The amount of PS released by roots under Fe or Zn stress was related to its contents in the roots before the onset of PS release, which starts 2 h after the onset of light and continues for the next 4 h. Both aestivum and durum wheat follow similar diurnal rhythm for PS release and its level in roots. These results suggest that the capacity for PS production and release is a limiting factor for Zn efficiency in graminaceous species.

  • Determination of Phytosiderophores by anion-exchange chromatography with pulsed amperometric detection.
    Journal of chromatography. A, 2001
    Co-Authors: Günther Weber, Günter Neumann, Charlotte Haake, Volker Römheld
    Abstract:

    Phytosiderophores of the mugineic acid family are separated by anion-exchange HPLC using NaOH gradient elution. Separation of mugineic acid (MA), 2′-deoxymugineic acid (DMA), 3-hydroxymugineic acid (HMA) and 3-epi-hydroxymugineic acid (epi-HMA) is obtained within 15 min. Detection of the underivatised Phytosiderophores is performed using pulsed amperometric detection (PAD) at pH 13. The sensitivity of the detection increases in the order DMA

Nicolaus Von Wirén - One of the best experts on this subject based on the ideXlab platform.

  • Uptake and apoplastic retention of EDTA‐ and phytosiderophore‐chelated chromium(III) in maize
    Journal of Plant Nutrition and Soil Science, 2007
    Co-Authors: B. Erenoglu, Volker Römheld, Hicham Khodr, Hemanta Kumar Patra, Nicolaus Von Wirén
    Abstract:

    Increasing the mobilization and root uptake of chromium (Cr) by synthetic and plant-borne chelators might be relevant for the design of phytoremediation strategies on Cr-contaminated sites. Short-term uptake studies in maize roots supplied with 51 CrCl 3 or 51 Cr(III)-EDTA led to higher apoplastic Cr contents in plant roots supplied with 51 CrCl 3 and in Fe-sufficient plants relative to Fe-deficient plants, indicating that Fe stimulated co-precipitation of Cr. Concentration-dependent retention of Cr in a methanol:chloroform-treated cell-wall fraction was still saturable and in agreement with the predicted tendency of Cr(lll) to precipitate as Cr(OH) 3 . To investigate a possible stimulation of Cr(lll) uptake by Phytosiderophores, Fe-deficient maize roots were exposed for 6 d to Cr(lll)-EDTA or Cr(lll)-DMA (2'-deoxymugineic acid). Relative to plants without Cr supply, the supply of both chelated Cr species in a subtoxic concentration of 1 μM resulted in alleviation of Fe deficiency-induced chlorosis and higher Cr accumulation. Long-term Cr accumulation from Cr(lll)-DMA was similar to that from Cr(lll)-EDTA, and Cr uptake from both chelates was not altered in the maize mutant ys1, which is defective in metal-phytosiderophore uptake. We therefore conclude that Phytosiderophores increase Cr solubility similar to synthetic chelators like EDTA, but do not additionally contribute to Cr(III) uptake from Cr-contaminated sites.

  • Iron acquisition by Phytosiderophores contributes to cadmium tolerance.
    Plant physiology, 2007
    Co-Authors: Anderson R. Meda, Gabriel Schaaf, B. Erenoglu, Enrico B. Scheuermann, Ulrich E. Prechsl, Heiko Hayen, Giinther Weber, Nicolaus Von Wirén
    Abstract:

    Based on the ability of Phytosiderophores to chelate other heavy metals besides iron (Fe), Phytosiderophores were suggested to prevent graminaceous plants from cadmium (Cd) toxicity. To assess interactions between Cd and phytosiderophore-mediated Fe acquisition, maize (Zea mays) plants were grown hydroponically under limiting Fe supply. Exposure to Cd decreased uptake rates of 59Fe(III)-Phytosiderophores and enhanced the expression of the Fe-phytosiderophore transporter gene ZmYS1 in roots as well as the release of the phytosiderophore 2′-deoxymugineic acid (DMA) from roots under Fe deficiency. However, DMA hardly mobilized Cd from soil or from a Cd-loaded resin in comparison to the synthetic chelators diaminetriaminepentaacetic acid and HEDTA. While nano-electrospray-high resolution mass spectrometry revealed the formation of an intact Cd(II)-DMA complex in aqueous solutions, competition studies with Fe(III) and zinc(II) showed that the formed Cd(II)-DMA complex was weak. Unlike HEDTA, DMA did not protect yeast (Saccharomyces cerevisiae) cells from Cd toxicity but improved yeast growth in the presence of Cd when yeast cells expressed ZmYS1. When supplied with Fe-DMA as a Fe source, transgenic Arabidopsis (Arabidopsis thaliana) plants expressing a cauliflower mosaic virus 35S-ZmYS1 gene construct showed less growth depression than wild-type plants in response to Cd. These results indicate that inhibition of ZmYS1-mediated Fe-DMA transport by Cd is not related to Cd-DMA complex formation and that Cd-induced phytosiderophore release cannot protect maize plants from Cd toxicity. Instead, phytosiderophore-mediated Fe acquisition can improve Fe uptake in the presence of Cd and thereby provides an advantage under Cd stress relative to Fe acquisition via ferrous Fe.

  • separation and identification of Phytosiderophores and their metal complexes in plants by zwitterionic hydrophilic interaction liquid chromatography coupled to electrospray ionization mass spectrometry
    Journal of Chromatography A, 2006
    Co-Authors: Yue Xuan, Nicolaus Von Wirén, Anderson R. Meda, Enrico B. Scheuermann, Heiko Hayen, Günther Weber
    Abstract:

    A sensitive method for the separation of different Phytosiderophores (PS) of the mugineic acid (MA) family, and the candidate ligand for intracellular metal transport in plants nicotianamine (NA), and respective metal complexes in plants by zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) coupled to electrospray ionization mass spectrometry (ESI-MS) is described. Separation of mugineic acid, 2'-deoxymugineic acid (DMA), 3-epi-hydroxymugineic acid (epi-HMA), nicotianamine, Fe(III)-DMA, Fe(III)-NA, M(II)-DMA, and M(II)-NA complexes (M(II)=Zn(II), Cu(II), Ni(II), and Fe(II)), was achieved within 22 min on the ZIC-HILIC column by using a gradient elution with a mobile phase consisting of ammonium acetate and acetonitrile at pH 7.3, at a flow rate of 0.15 mL/min. The on-line coupling to ESI-MS in the negative ionization mode enables the detection of these compounds in the micromol/L range, which is the relevant concentration range in real plant samples. DMA-complexes of Fe(III), Zn, and Cu in wheat root, and an NA-complex of Ni in Arabidopsis were detected and identified by the proposed method. Even in the case of partial coelution of some divalent metal complexes, the identification is possible by their distinct mass spectra. The stability of metal complexes during separation was checked by injecting ethylenediaminetetraacetic acid (EDTA) after each run of metal-phytosiderophore complexes. Good stability of divalent-Phytosiderophores, except for Fe(II)-complexes, was observed. During gradient separation, Fe(III)-complexes are partly dissociated (<20%), but a good sensitivity of Fe(III)-DMA in real plant samples is still achieved. In order to avoid instability problems with the separation of Fe-complexes, an isocratic separation is proposed, which allows the separation of ferrous and ferric complexes in 2 min.

  • Separation and identification of Phytosiderophores and their metal complexes in plants by zwitterionic hydrophilic interaction liquid chromatography coupled to electrospray ionization mass spectrometry.
    Journal of chromatography. A, 2006
    Co-Authors: Yue Xuan, Nicolaus Von Wirén, Anderson R. Meda, Enrico B. Scheuermann, Heiko Hayen, Günther Weber
    Abstract:

    A sensitive method for the separation of different Phytosiderophores (PS) of the mugineic acid (MA) family, and the candidate ligand for intracellular metal transport in plants nicotianamine (NA), and respective metal complexes in plants by zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) coupled to electrospray ionization mass spectrometry (ESI-MS) is described. Separation of mugineic acid, 2'-deoxymugineic acid (DMA), 3-epi-hydroxymugineic acid (epi-HMA), nicotianamine, Fe(III)-DMA, Fe(III)-NA, M(II)-DMA, and M(II)-NA complexes (M(II)=Zn(II), Cu(II), Ni(II), and Fe(II)), was achieved within 22 min on the ZIC-HILIC column by using a gradient elution with a mobile phase consisting of ammonium acetate and acetonitrile at pH 7.3, at a flow rate of 0.15 mL/min. The on-line coupling to ESI-MS in the negative ionization mode enables the detection of these compounds in the micromol/L range, which is the relevant concentration range in real plant samples. DMA-complexes of Fe(III), Zn, and Cu in wheat root, and an NA-complex of Ni in Arabidopsis were detected and identified by the proposed method. Even in the case of partial coelution of some divalent metal complexes, the identification is possible by their distinct mass spectra. The stability of metal complexes during separation was checked by injecting ethylenediaminetetraacetic acid (EDTA) after each run of metal-phytosiderophore complexes. Good stability of divalent-Phytosiderophores, except for Fe(II)-complexes, was observed. During gradient separation, Fe(III)-complexes are partly dissociated (

  • Physiological and biochemical characterization of metal-phytosiderophore transport in graminaceous species
    Soil Science and Plant Nutrition, 2004
    Co-Authors: Gabriel Schaaf, B. Erenoglu, Nicolaus Von Wirén
    Abstract:

    Abstract Physiological studies on the uptake of metal-Phytosiderophores in strategy II plants indicated that besides iron-Phytosiderophores also other phytosiderophore-chelated metals can be taken up. To verify whether this reflects a property of the recently isolated Fe(Ill)-phytosiderophore transporter ZmYS1, a biochemical study was undertaken using growth complementation of yeast mutants and two-electrode voltage clamp in Xenopus oocytes. These approaches allowed to show that ZmYS1 indeed transports other phytosiderophore-chelated metals, such as Cu, Zn, Co, or Ni, as well as nicotianamine-complexes with Fe(II), Fe(III), and Ni(II). Moreover, it was shown that Fe(III)-DMA is cotransported with protons by ZmYS1, thus allowing substrate transport to be driven by the negative membrane potential. Despite the transport of a broad range of phytosiderophore-chelated heavy metals, neither Zn nor Mn or Cu deficiency led to an upregulation of ZmYS1 transcript levels in leaves or roots of maize. It is therefore c...

Naoko K Nishizawa - One of the best experts on this subject based on the ideXlab platform.

  • Characterizing the Crucial Components of Iron Homeostasis in the Maize Mutants ys1 and ys3
    2016
    Co-Authors: Tomoko Nozoye, Hiromi Nakanishi, Naoko K Nishizawa
    Abstract:

    To acquire iron (Fe), graminaceous plants secrete mugineic acid family Phytosiderophores through the phytosiderophore efflux transporter TOM1 and take up Fe in the form of Fe(III)–phytosiderophore complexes. Yellow stripe 1 (ys1) and ys3 are recessive mutants of maize (Zea mays L.) that show typical symptoms of Fe deficiency, i.e., interveinal chlorosis of the leaves. The ys1 mutant is defective in the Fe(III)–phytosiderophore transporter YS1 and is therefore unable to take up Fe(III)– phytosiderophore complexes. While the ys3 mutant has been shown to be defective in Phytosiderophores release, the causative gene has not been identified. The present study was performed to characterize the expression profiles of the genes in ys1 and ys3 mutants to extend our understanding of Fe homeostasis in maize. Using quantitative real-time polymerase chain reaction, we assessed changes in the levels of gene expression in response to Fe deficiency of genes involved in Fe homeostasis, such as those related to phytosiderophore biosynthesis and Fe transport. As with other crops, these Fe deficiency-inducible genes were also upregulated in maize. In addition, these Fe deficiency-inducible genes were upregulated in both the ys1 and ys3mutants, even under Fe-sufficient conditions. Indeed, the Fe concentrations in the roots of ys1 and ys3 plants were lower than that of wild-type controls. These results suggest that ys1 and ys3 are Fe-deficient during growth in the presence of Fe. In agreement with previous reports, the level of YS1 expression decreased in the ys1 mutant. Moreover, the expression level of a homolog of TOM1 in maize decreased significantly in the ys3 mutant. Unsplice

  • The Phytosiderophore Efflux Transporter TOM2 Is Involved in Metal Transport in Rice
    The Journal of biological chemistry, 2015
    Co-Authors: Tomoko Nozoye, Takanori Kobayashi, Hiromi Nakanishi, Seiji Nagasaka, Yuki Sato, Nobuyuki Uozumi, Naoko K Nishizawa
    Abstract:

    Iron is an essential metal element for all living organisms. Graminaceous plants produce and secrete mugineic acid family Phytosiderophores from their roots to acquire iron in the soil. Phytosiderophores chelate and solubilize insoluble iron hydroxide in the soil. Subsequently, plants take up iron-phytosiderophore complexes through specific transporters on the root cell membrane. Phytosiderophores are also thought to be important for the internal transport of various transition metals, including iron. In this study, we analyzed TOM2 and TOM3, rice homologs of transporter of mugineic acid family Phytosiderophores 1 (TOM1), a crucial efflux transporter directly involved in phytosiderophore secretion into the soil. Transgenic rice analysis using promoter-β-glucuronidase revealed that TOM2 was expressed in tissues involved in metal translocation, whereas TOM3 was expressed only in restricted parts of the plant. Strong TOM2 expression was observed in developing tissues during seed maturation and germination, whereas TOM3 expression was weak during seed maturation. Transgenic rice in which TOM2 expression was repressed by RNA interference showed growth defects compared with non-transformants and TOM3-repressed rice. Xenopus laevis oocytes expressing TOM2 released (14)C-labeled deoxymugineic acid, the initial phytosiderophore compound in the biosynthetic pathway in rice. In onion epidermal and rice root cells, the TOM2-GFP fusion protein localized to the cell membrane, indicating that the TOM2 protein is a transporter for phytosiderophore efflux to the cell exterior. Our results indicate that TOM2 is involved in the internal transport of deoxymugineic acid, which is required for normal plant growth.

  • Molecular evidence for phytosiderophore-induced improvement of iron nutrition of peanut intercropped with maize in calcareous soil.
    Plant cell & environment, 2013
    Co-Authors: Hongchun Xiong, Yusuke Kakei, Takanori Kobayashi, Hiromi Nakanishi, Xiaotong Guo, Mikio Nakazono, Hirokazu Takahashi, Hongyun Shen, Fusuo Zhang, Naoko K Nishizawa
    Abstract:

    Peanut/maize intercropping is a sustainable and effective agroecosystem that evidently enhances the Fe nutrition of peanuts in calcareous soils. So far, the mechanism involved in this process has not been elucidated. In this study, we unravel the effects of Phytosiderophores in improving Fe nutrition of intercropped peanuts in peanut/maize intercropping. The maize ys3 mutant, which cannot release Phytosiderophores, did not improve Fe nutrition of peanut, whereas the maize ys1 mutant, which can release Phytosiderophores, prevented Fe deficiency, indicating an important role of Phytosiderophores in improving the Fe nutrition of intercropped peanut. Hydroponic experiments were performed to simplify the intercropping system, which revealed that Phytosiderophores released by Fe-deficient wheat promoted Fe acquisition in nearby peanuts and thus improved their Fe nutrition. Moreover, the phytosiderophore deoxymugineic acid (DMA) was detected in the roots of intercropped peanuts. The yellow stripe1-like (YSL) family of genes, which are homologous to maize yellow stripe 1 (ZmYS1), were identified in peanut roots. Further characterization indicated that among five AhYSL genes, AhYSL1, which was localized in the epidermis of peanut roots, transported Fe(III)-DMA. These results imply that in alkaline soil, Fe(III)-DMA dissolved by maize might be absorbed directly by neighbouring peanuts in the peanut/maize intercropping system.

  • Characterizing the Crucial Components of Iron Homeostasis in the Maize Mutants ys1 and ys3
    2013
    Co-Authors: Tomoko Nozoye, Hiromi Nakanishi, Naoko K Nishizawa
    Abstract:

    To acquire iron (Fe), graminaceous plants secrete mugineic acid family Phytosiderophores through the phytosiderophore efflux transporter TOM1 and take up Fe in the form of Fe(III)–phytosiderophore complexes. Yellow stripe 1 (ys1) and ys3 are recessive mutants of maize (Zea mays L.) that show typical symptoms of Fe deficiency, i.e., interveinal chlorosis of the leaves. The ys1 mutant is defective in the Fe(III)–phytosiderophore transporter YS1 and is therefore unable to take up Fe(III)–phytosiderophore complexes. While the ys3 mutant has been shown to be defective in Phytosiderophores release, the causative gene has not been identified. The present study was performed to characterize the expression profiles of the genes in ys1 and ys3 mutants to extend our understanding of Fe homeostasis in maize. Using quantitative real-time polymerase chain reaction, we assessed changes in the levels of gene expression in response to Fe deficiency of genes involved in Fe homeostasis, such as those related to phytosiderophore biosynthesis and Fe transport. As with other crops, these Fe deficiency-inducible genes were also upregulated in maize. In addition, these Fe deficiency-inducible genes were upregulated in both the ys1 and ys3 mutants, even under Fe-sufficient conditions. Indeed, the Fe concentrations in the roots of ys1 and ys3 plants were lower than that of wild-type controls. These results suggest that ys1 and ys3 are Fe-deficient during growth in the presence of Fe. In agreement with previous reports, the level of YS1 expression decreased in the ys1 mutant. Moreover, the expression level of a homolog of TOM1 in maize decreased significantly in the ys3 mutant. Unspliced introns of ZmTOM1 were detected only in ys3, and not in YS1YS3 or ys1, suggesting that ZmTOM1 may be involved in the ys3 phenotype.

  • Phytosiderophore efflux transporters are crucial for iron acquisition in graminaceous plants
    The Journal of biological chemistry, 2010
    Co-Authors: Tomoko Nozoye, Takanori Kobayashi, Hiromi Nakanishi, Michiko Takahashi, Seiji Nagasaka, Yuki Sato, Nobuyuki Uozumi, Yoko Sato, Naoko K Nishizawa
    Abstract:

    Eukaryotic organisms have developed diverse mechanisms for the acquisition of iron, which is required for their survival. Graminaceous plants use a chelation strategy. They secrete phytosiderophore compounds, which solubilize iron in the soil, and then take up the resulting iron-phytosiderophore complexes. Bacteria and mammals also secrete siderophores to acquire iron. Although phytosiderophore secretion is crucial for plant growth, its molecular mechanism remains unknown. Here, we show that the efflux of deoxymugineic acid, the primary phytosiderophore from rice and barley, involves the TOM1 and HvTOM1 genes, respectively. Xenopus laevis oocytes expressing TOM1 or HvTOM1 released 14C-labeled deoxymugineic acid but not 14C-labeled nicotianamine, a structural analog and biosynthetic precursor of deoxymugineic acid, indicating that the TOM1 and HvTOM1 proteins are the phytosiderophore efflux transporters. Under conditions of iron deficiency, rice and barley roots express high levels of TOM1 and HvTOM1, respectively, and the overexpression of these genes increased tolerance to iron deficiency. In rice roots, the efficiency of deoxymugineic acid secretion was enhanced by overexpression of TOM1 and decreased by its repression, providing further evidence that TOM1 encodes the efflux transporter of deoxymugineic acid. We have also identified two genes encoding efflux transporters of nicotianamine, ENA1 and ENA2. Our identification of phytosiderophore efflux transporters has revealed the final piece in the molecular machinery of iron acquisition in graminaceous plants.

Horst Marschner - One of the best experts on this subject based on the ideXlab platform.

  • Roots of Iron-Efficient Maize also Absorb Phytosiderophore-Chelated Zinc
    Plant physiology, 1996
    Co-Authors: N. Von Wiren, Horst Marschner, Volker Römheld
    Abstract:

    To investigate the recognition of Zn-Phytosiderophores by the putative Fe-phytosiderophore transporter in maize (Zea mays L.) roots, short-term uptake of 65Zn-labeled Phytosiderophores was compared in the Fe-efficient maize cultivar Alice and the maize mutant ys1 carrying a defect in Fe-phytosiderophore uptake. In ys1, uptake and translocation rates of Zn from Zn-Phytosiderophores were one-half of those in Alice, but no genotypical difference was found in Zn uptake and translocation from other Zn-binding forms. In ys1 and in tendency also in Alice, Zn uptake decreased with increasing stability constant of the chelate in the order: ZnSO4 [greater than or equal to] Zn-desferrioxamine > Zn-Phytosiderophores > Zn-EDTA. Adding a 500-fold excess of free Phytosiderophores over Zn to the uptake solution depressed Zn uptake in ys1 almost completely. In uptake studies with double-labeled 65Zn-14C-Phytosiderophores, ys1 absorbed the phytosiderophore at similar rates when supplied as a Zn-chelate or the free ligand. By contrast, in Alice 14C-phytosiderophore uptake from the Zn-chelate was 2.8-fold higher than from the free ligand, suggesting that Alice absorbed the complete Zn-phytosiderophore complex via the putative plasma membrane transporter for Fe-Phytosiderophores. We propose two pathways for the uptake of Zn from Zn-Phytosiderophores in grasses, one via the transport of the free Zn cation and the other via the uptake of nondissociated Zn-Phytosiderophores.

  • Zinc-efficient wild grasses enhance release of Phytosiderophores under zinc deficiency
    Journal of Plant Nutrition, 1996
    Co-Authors: Ismail Cakmak, Horst Marschner, Levent Ozturk, Sema Karanlik, Hasan Ekiz
    Abstract:

    Abstract The effect of the zinc (Zn) nutritional status on the rate of phyto‐siderophore release was studied in three wild grass species (Hordeum murinum, Agropyron orientale, and Secale cereale) grown in nutrient solution under co‐trolled environmental conditions. These wild grasses are highly “Zn‐efficient”; and grow well on severely Zn‐deficient calcareous soils in Turkey (DTPA‐extractable Zn was 0.12 mg/kg soil and CaCO3 was 37%). In all wild grasses studied, Zn deficiency reduced shoot growth but had no effect on root growth. Low amounts of Phytosiderophores were released from roots of all wild grasses adequately supplied with Zn. In plants grown without Zn, release of Phytosiderophores progressively increased with the onset of visual Zn deficiency symptoms, such as inhibition of shoot elongation and appearance of chlorotic and necrotic patches on leaves. Compared to Zn‐sufficient plants, phytosiderophore release increased 18–20‐fold in deficient plants. HPLC analysis of root exudates showed that the...

  • uptake kinetics of iron Phytosiderophores in two maize genotypes differing in iron efficiency
    Physiologia Plantarum, 1995
    Co-Authors: Nicolaus Von Wirén, Horst Marschner, Volker Römheld
    Abstract:

    Iron inefficiency in the maize (Zea mays L.) mutant ysl is caused by a defect in the uptake system for Fe-Phytosiderophores. To characterize this defect further, the uptake kinetics of Fe-Phytosiderophores in ysl was compared to the Fe-efficient maize cultivar Alice. Short-term uptake of 59 Fe-labeled Fe-deoxymugineic acid (Fe-DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe- deficient plants followed Michaelis-Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe-Phytosiderophores. The saturable component had similar K m (∼ 10 μM in both genotypes. In contrast, V max was 5.5 μmol Fe-DMA g −1 dry weight [30 min] −1 in Alice, but only 0.6 μmol Fe-DMA g −1 dry weight [30 min] −1 in ysl. Uptake experiments with double-labeled 59 Fe-[ 14 C]DMA suggest that in both cultivars Fe-DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high-affinity and a low-affinity uptake system mediating Fe-phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency in ysl affected high-affinity uptake and led to a decrease in activity and/or number of Fe-phytosiderophore transporters

  • Uptake kinetics of iron‐Phytosiderophores in two maize genotypes differing in iron efficiency
    Physiologia Plantarum, 1995
    Co-Authors: Nicolaus Von Wirén, Horst Marschner, Volker Römheld
    Abstract:

    Iron inefficiency in the maize (Zea mays L.) mutant ysl is caused by a defect in the uptake system for Fe-Phytosiderophores. To characterize this defect further, the uptake kinetics of Fe-Phytosiderophores in ysl was compared to the Fe-efficient maize cultivar Alice. Short-term uptake of 59 Fe-labeled Fe-deoxymugineic acid (Fe-DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe- deficient plants followed Michaelis-Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe-Phytosiderophores. The saturable component had similar K m (∼ 10 μM in both genotypes. In contrast, V max was 5.5 μmol Fe-DMA g −1 dry weight [30 min] −1 in Alice, but only 0.6 μmol Fe-DMA g −1 dry weight [30 min] −1 in ysl. Uptake experiments with double-labeled 59 Fe-[ 14 C]DMA suggest that in both cultivars Fe-DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high-affinity and a low-affinity uptake system mediating Fe-phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency in ysl affected high-affinity uptake and led to a decrease in activity and/or number of Fe-phytosiderophore transporters

  • Iron Inefficiency in Maize Mutant ys1 (Zea mays L. cv Yellow-Stripe) Is Caused by a Defect in Uptake of Iron Phytosiderophores
    Plant physiology, 1994
    Co-Authors: N. Von Wiren, Satoshi Mori, Horst Marschner, Volker Römheld
    Abstract:

    To determine the Fe inefficiency factors in the maize mutant ys1 (Zea mays L. cv Yellow Stripe), root exudates of Fe-inefficient ys1 and of two Fe-efficient maize cultivars (Alice, WF9) were collected in axenic nutrient solution cultures. Analysis by thin-layer chromatography and high-performance liquid chromatography revealed that under Fe deficiency ys1 released the phytosiderophore 2[prime]-deoxymugineic acid (DMA) in quantities similar to those of Alice and WF9. Under nonaxenic conditions, DMA released by plants of all three cultivars was rapidly decomposed by microorganisms in the nutrient solution. Uptake experiments with 59Fe-labeled DMA, purified from root exudates of either Fe-deficient Alice or ys1 plants, showed up to 20 times lower uptake and translocation of 59Fe in ys1 than in Alice or WF9 plants. The presence of microorganisms during preculture and short-term uptake experiments had no significant effect on uptake and translocation rates of 59Fe in Alice and ys1 plants. We conclude that Fe inefficiency in the maize mutant ys1 is the result of a defect in the uptake system for Fe-Phytosiderophores.

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  • Further characterization of ferric—phytosiderophore transporters ZmYS1 and HvYS1 in maize and barley
    Journal of experimental botany, 2009
    Co-Authors: Daisei Ueno, Naoki Yamaji, Jian Feng
    Abstract:

    Roots of some gramineous plants secrete Phytosiderophores in response to iron deficiency and take up Fe as a ferric–phytosiderophore complex through the transporter YS1 (Yellow Stripe 1). Here, this transporter in maize (ZmYS1) and barley (HvYS1) was further characterized and compared in terms of expression pattern, diurnal change, and tissue-type specificity of localization. The expression of HvYS1 was specifically induced by Fe deficiency only in barley roots, and increased with the progress of Fe deficiency, whereas ZmYS1 was expressed in maize in the leaf blades and sheaths, crown, and seminal roots, but not in the hypocotyl. HvYS1 expression was not induced by any other metal deficiency. Furthermore, in maize leaf blades, the expression was higher in the young leaf blades showing severe chlorosis than in the old leaf blades showing no chlorosis. The expression of HvYS1 showed a distinct diurnal rhythm, reaching a maximum before the onset of phytosiderophore secretion. In contrast, ZmYS1 did not show such a rhythm in expression. Immunostaining showed that ZmYS1 was localized in the epidermal cells of both crown and lateral roots, with a polar localization at the distal side of the epidermal cells. In maize leaves, ZmYS1 was localized in mesophyll cells, but not epidermal cells. These differences in gene expression pattern and tissue-type specificity of localization suggest that HvYS1 is only involved in primary Fe acquisition by barley roots, whereas ZmYS1 is involved in both primary Fe acquisition and intracellular transport of iron and other metals in maize.

  • Secretion time of phytosiderophore differs in two perennial grasses and is controlled by temperature
    Plant and Soil, 2009
    Co-Authors: Daisei Ueno, Jian Feng
    Abstract:

    Some perennial grasses secrete Phytosiderophores from the roots in response to Fe-deficiency. Here, we characterized the pattern of phytosiderophore secretion by Lolium perenne (cv. ‘Tove’) and Poa pratensis (cv. ‘Baron’), which are used to correct iron-deficiency induced chlorosis in fruit trees grown on calcareous soils. Both species showed a distinct diurnal rhythm in phytosiderophore secretion, but the secretion time differed between species; the secretion peak time was about 2 h earlier in L. perenne than in P. pratensis under the same growth conditions. The secretion time was shifted by changing temperature during the collection of Phytosiderophores in both L. perenne and P. pratensis. Increasing root-zone temperature resulted in earlier secretion, while lowering the temperature resulted in delayed secretion. Furthermore, this shift of secretion time was achieved by changing the temperature around the root-zone. Shading treatment during the secretion period did not affect the secretion time in either species. These results indicate that the secretion of phytosiderophore is triggered by the temperature around the roots, but not light, in these two perennial grasses.

  • Identification of two novel Phytosiderophores secreted by perennial grasses.
    The New phytologist, 2007
    Co-Authors: Daisei Ueno, Takashi Iwashita, Kyosuke Nomoto, A.d. Rombola, Jian Feng
    Abstract:

    It has been suggested that some perennial grasses secrete Phytosiderophores in response to iron (Fe) deficiency, but the compounds have not been identified. Here, we identified and characterized the Phytosiderophores secreted by two perennial grasses, Lolium perenne cv. Tove and Poa pratensis cv. Baron. Root exudates were collected from the roots of Fe-deficient grasses and then purified with various chromatographies. The structure of the purified compounds was determined using both nuclear magnetic resonance and fast atom bombardment mass spectrometry. Both species secreted Phytosiderophores in response to Fe deficiency, and the amount of Phytosiderophores secreted increased with the development of Fe deficiency. The type of Phytosiderophores secreted differed with plant species; L. perenne cv. Tove secreted 3-epihydroxy-2'-deoxymugineic acid (epiHDMA), 2'-deoxymugineic acid (DMA) and an unknown compound, whereas P. pratensis cv. Baron secreted DMA, avenic acid A (AVA) and an unknown compound. Purification and subsequent analysis with nuclear magnetic resonance and mass led to identification of the two novel Phytosiderophores; 3-hydroxy-2'-deoxymugineic acid (HDMA) from L. perenne, and 2'-hydroxyavenic acid A (HAVA) from P. pratensis. Both novel Phytosiderophores have similar chelating activity to known Phytosiderophores.

  • A specific transporter for iron(III)-phytosiderophore in barley roots.
    The Plant journal : for cell and molecular biology, 2006
    Co-Authors: Yoshiko Murata, Jian Feng, Daisei Ueno, Kyosuke Nomoto, Naoki Yamaji, Takashi Iwashita
    Abstract:

    Iron acquisition of graminaceous plants is characterized by the synthesis and secretion of the iron-chelating phytosiderophore, mugineic acid (MA), and by a specific uptake system for iron(III)-phytosiderophore complexes. We identified a gene specifically encoding an iron-phytosiderophore transporter (HvYS1) in barley, which is the most tolerant species to iron deficiency among graminaceous plants. HvYS1 was predicted to encode a polypeptide of 678 amino acids and to have 72.7% identity with ZmYS1, a first protein identified as an iron(III)-phytosiderophore transporter in maize. Real-time RT-PCR analysis showed that the HvYS1 gene was mainly expressed in the roots, and its expression was enhanced under iron deficiency. In situ hybridization analysis of iron-deficient barley roots revealed that the mRNA of HvYS1 was localized in epidermal root cells. Furthermore, immunohistological staining with anti-HvYS1 polyclonal antibody showed the same localization as the mRNA. HvYS1 functionally complemented yeast strains defective in iron uptake on media containing iron(III)-MA, but not iron-nicotianamine (NA). Expression of HvYS1 in Xenopus oocytes showed strict specificity for both metals and ligands: HvYS1 transports only iron(III) chelated with phytosiderophore. The localization and substrate specificity of HvYS1 is different from those of ZmYS1, indicating that HvYS1 is a specific transporter for iron(III)-phytosiderophore involved in primary iron acquisition from soil in barley roots.

  • Biosynthesis of Phytosiderophores in several Triticeae species with different genomes
    Journal of Experimental Botany, 1999
    Co-Authors: Jian Feng, Shin Taketa, Yi Chieh Chang, Kazuyoshi Takeda, Hideaki Matsumoto
    Abstract:

    To examine variation in phytosiderophore biosynthesis in Triticeae, Phytosiderophores were investigated in wild and cultivated species of wheat and barley with different genomes. All wheats tested including hexaploid (AABBDD), tetraploid (AABB), and diploid (AA or DD) lines produced only one phytosiderophore, 2'-deoxymugineic acid. The Phytosiderophores biosynthesized in wild barleys varied among species. Using substitution-type triticale lines and wheat-barley addition lines, it was revealed that, in triticale, genes for the biosynthesis of both mugineic and hydroxymugineic acids were located in the long arm of chromosome 5R and that, in barley, the gene for production of mugineic acid was located in the long arm of chromosome 4H.