Transport of metal micronutrients in the phloem of castor bean (Ricinus communis) seedlings

Schmidke, Ilka; Stephan, Udo W.

doi:10.1034/j.1399-3054.1995.950122.x

Cited by 16 publications

(15 citation statements)

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“…Metals exiting the leaves during senescence are likely to do so by way of the phloem. Recent studies of metal transport in castor bean indicate that copper and iron can move through phloem chelated to organic molecules, in particular the amino acid nicotianamine (Schmidke and Stephan, 1995).…”

Section: Discussionmentioning

confidence: 99%

Identification of a Functional Homolog of the Yeast Copper Homeostasis Gene ATX1 from Arabidopsis1

et al. 1998

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A cDNA clone encoding a homolog of the yeast (Saccharomyces cerevisiae) gene Anti-oxidant 1 (ATX1) has been identified from Arabidopsis. This gene, referred to as Copper CHaperone (CCH), encodes a protein that is 36% identical to the amino acid sequence of ATX1 and has a 48-amino acid extension at the C-terminal end, which is absent from ATX1 homologs identified in animals. ATX1-deficient yeast (atx1) displayed a loss of high-affinity iron uptake. Expression of CCH in the atx1 strain restored high-affinity iron uptake, demonstrating that CCH is a functional homolog of ATX1. When overexpressed in yeast lacking the superoxide dismutase gene SOD1, both ATX1 and CCH protected the cell from the reactive oxygen toxicity that results from superoxide dismutase deficiency. CCH was unable to rescue the sod1 phenotype in the absence of copper, indicating that CCH function is copper dependent. In Arabidopsis CCH mRNA is present in the root, leaf, and inflorescence and is up-regulated 7-fold in leaves undergoing senescence. In plants treated with 800 nL/L ozone for 30 min, CCH mRNA levels increased by 30%. In excised leaves and whole plants treated with high levels of exogenous CuSO 4 , CCH mRNA levels decreased, indicating that CCH is regulated differently than characterized metallothionein proteins in Arabidopsis.

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Section: Discussionmentioning

confidence: 99%

Identification of a Functional Homolog of the Yeast Copper Homeostasis Gene ATX1 from Arabidopsis1

et al. 1998

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“…Methods described previously were used to analyze the total iron content in leaf tissues (Schmidke and Stephan, 1995); nicotinamine (Schmidke and Stephan 1995); ascorbic acid and glutathione (Davey et al, 1999); activities of catalase, ascorbate peroxidase, and aconitase (De Bellis et al, 1993;Kampfenkel et al, 1995); superoxide dismutase isoforms by PAGE under native conditions (Kliebenstein et al, 1998); Fe-chelatase activity (Papenbrock et al, 1999); and abasic sites in DNA after modification with an aldehyde-reactive probe, ARP (Dojindo Laboratories, Kumamoto, Japan) (Nakamura et al 1998). RNA was extracted from 3-week-old seedlings grown in vitro and analyzed by gel blot hybridization as described (Babiychuk et al, 1998).…”

Section: Other Methodsmentioning

confidence: 99%

A Mutation of the Mitochondrial ABC Transporter Sta1 Leads to Dwarfism and Chlorosis in the Arabidopsis Mutant starik

et al. 2001

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A mutation in the Arabidopsis gene STARIK leads to dwarfism and chlorosis of plants with an altered morphology of leaf and cell nuclei. We show that the STARIK gene encodes the mitochondrial ABC transporter Sta1 that belongs to a subfamily of Arabidopsis half-ABC transporters. The severity of the starik phenotype is suppressed by the ectopic expression of the STA2 homolog; thus, Sta1 function is partially redundant. Sta1 supports the maturation of cytosolic Fe/S protein in ⌬ atm1 yeast, substituting for the ABC transporter Atm1p. Similar to Atm1p-deficient yeast, mitochondria of the starik mutant accumulated more nonheme, nonprotein iron than did wild-type organelles. We further show that plant mitochondria contain a putative L -cysteine desulfurase. Taken together, our results suggest that plant mitochondria possess an evolutionarily conserved Fe/S cluster biosynthesis pathway, which is linked to the intracellular iron homeostasis by the function of Atm1p-like ABC transporters. INTRODUCTIONABC transporters constitute one of the largest protein families with diverse functions in membrane transport. The designation of ABC transporter recognizes a highly conserved ATP binding cassette, which is the most characteristic feature of this superfamily. These proteins mediate the relatively specific, active transmembrane transport of molecules that can range in size from small ions to proteins (reviewed in Higgins, 1992) and utilize the energy of ATP hydrolysis to pump substrates across membranes, usually against a concentration gradient. The typical ABC transporter consists of four domains. Two of these domains are hydrophobic, and each comprises six membrane-spanning segments. The transmembrane domains are believed to form a channel and to determine the specificity of the transporter. The other two domains are located at the periphery of the membrane and couple ATP hydrolysis to the transport process.The ABC transporter Atm1p of budding yeast mitochondria represents a "half-transporter" in which one transmembrane and one ATP binding domain are expressed in a single polypeptide (Leighton and Schatz, 1995). Atm1p is localized in the mitochondrial inner membrane and is believed to function as an exporter, because its ABC domains face the mitochondrial matrix. The ATM1 loss-of-function results in respiration-deficient mitochondria that lack cytochromes (Leighton and Schatz, 1995; Kispal et al., 1997) and that tend to loose their DNA (Leighton and Schatz, 1995). These pleiotropic effects of the Atm1p deficiency are generally attributed to the fact that in ⌬ atm1 cells, mitochondria accumulate up to 30-fold higher levels of iron than do wild-type organelles (Kispal et al., 1997;Mitsuhashi et al., 2000). The Atm1p transport function appears to be conserved in eukaryotes, and the human mitochondrial ABC transporters Abc7 and MTABC3 have been shown to be true functional orthologs of the Atm1p (Csere et al., 1998;Mitsuhashi et al., 2000). The human ABC7 gene has been implicated in hereditary X-linked sideroblastic anemia and a...

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“…However, the nonproteogenic amino acid nicotianamine (NA) seems to play an important role in metal homeostasis of plants. According to several studies, it binds iron, Zn, and Cu, mainly for long-distance transport in the vascular bundle (Stephan and Scholz, 1993;Pich et al, 1994;Schmidke and Stephan, 1995;Stephan et al, 1996, Pich andvon Wiren et al, 1999;Liao et al, 2000), and NA synthase has been shown to be highly overexpressed in hyperaccumulators compared with nonaccumulator plants (Becher et al, 2004;Weber et al, 2004;van de Mortel et al, 2006van de Mortel et al, , 2008.…”

mentioning

confidence: 99%

Complexation and Toxicity of Copper in Higher Plants. II. Different Mechanisms for Copper versus Cadmium Detoxification in the Copper-Sensitive Cadmium/Zinc Hyperaccumulator Thlaspi caerulescens (Ganges Ecotype)

et al. 2009

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The cadmium/zinc hyperaccumulator Thlaspi caerulescens is sensitive toward copper (Cu) toxicity, which is a problem for phytoremediation of soils with mixed contamination. Cu levels in T. caerulescens grown with 10 mM Cu 2+ remained in the nonaccumulator range (,50 ppm), and most individuals were as sensitive toward Cu as the related nonaccumulator Thlaspi fendleri. Obviously, hyperaccumulation and metal resistance are highly metal specific. Cu-induced inhibition of photosynthesis followed the "sun reaction" type of damage, with inhibition of the photosystem II reaction center charge separation and the water-splitting complex. A few individuals of T. caerulescens were more Cu resistant. Compared with Cu-sensitive individuals, they recovered faster from inhibition, at least partially by enhanced repair of chlorophyll-protein complexes but not by exclusion, since the content of Cu in their shoots was increased by about 25%. Extended x-ray absorption fine structure (EXAFS) measurements on frozen-hydrated leaf samples revealed that a large proportion of Cu in T. caerulescens is bound by sulfur ligands. This is in contrast to the known binding environment of cadmium and zinc in the same species, which is dominated by oxygen ligands. Clearly, hyperaccumulators detoxify hyperaccumulated metals differently compared with nonaccumulated metals. Furthermore, strong features in the Cu-EXAFS spectra ascribed to metal-metal contributions were found, in particular in the Cu-resistant specimens. Some of these features may be due to Cu binding to metallothioneins, but a larger proportion seems to result from biomineralization, most likely Cu(II) oxalate and Cu(II) oxides. Additional contributions in the EXAFS spectra indicate complexation of Cu(II) by the nonproteogenic amino acid nicotianamine, which has a very high affinity for Cu(II) as further characterized here.

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Transport of metal micronutrients in the phloem of castor bean (Ricinus communis) seedlings

Cited by 16 publications

References 0 publications

Identification of a Functional Homolog of the Yeast Copper Homeostasis Gene ATX1 from Arabidopsis1

Identification of a Functional Homolog of the Yeast Copper Homeostasis Gene ATX1 from Arabidopsis1

A Mutation of the Mitochondrial ABC Transporter Sta1 Leads to Dwarfism and Chlorosis in the Arabidopsis Mutant starik

Complexation and Toxicity of Copper in Higher Plants. II. Different Mechanisms for Copper versus Cadmium Detoxification in the Copper-Sensitive Cadmium/Zinc Hyperaccumulator Thlaspi caerulescens (Ganges Ecotype)

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