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ZmYS1 functions as a proton-coupled symporter for phytosiderophore- and nicotianamine-chelated metals.

Schaaf, Gabriel and Ludewig, Uwe and Erenoglu, Bülent E. and Mori, Satoshi and Kitahara, Takeshi and von Wirén, Nicolaus (2004):
ZmYS1 functions as a proton-coupled symporter for phytosiderophore- and nicotianamine-chelated metals.
In: The Journal of biological chemistry, pp. 9091-6, 279, (10), ISSN 0021-9258,
[Article]

Abstract

Among higher plants graminaceous species have the unique ability to efficiently acquire iron from alkaline soils with low iron solubility by secreting phytosiderophores, which are hexadentate metal chelators with high affinity for Fe(III). Iron(III)-phytosiderophores are subsequently taken up by roots via YS1 transporters, that belong to the OPT oligopeptide transporter family. Despite its physiological importance at alkaline pH, uptake of Fe-phytosiderophores into roots of wild-type maize plants was greater at acidic pH and sensitive to the proton uncoupler CCCP. To access the mechanism of Fe-phytosiderophore acquisition, ZmYS1 was expressed in an iron uptake-defective yeast mutant and in Xenopus oocytes, where ZmYS1-dependent Fe-phytosiderophore transport was stimulated at acidic pH and sensitive to CCCP. Electrophysiological analysis in oocytes demonstrated that Fephytosiderophore transport depends on proton cotransport and on the membrane potential, which allows ZmYS1-mediated transport even at alkaline pH. We further investigated substrate specificity and observed that ZmYS1 complemented the growth defect of the zinc uptake-defective yeast mutant zap1 and transported various phytosiderophore-bound metals into oocytes, including zinc, copper, nickel, and, at a lower rate, also manganese and cadmium. Unexpectedly, ZmYS1 also transported Ni(II), Fe(II), and Fe(III) complexes with nicotianamine, a structural analog of phytosiderophores, which has been shown to act as an intracellular metal chelator in all higher plants. Our results show that ZmYS1 encodes a proton-coupled broad-range metal-phytosiderophore transporter that additionally transports Fe- and Ni-nicotianamine. These biochemical properties indicate a novel role of YS1 transporters for heavy metal homeostasis in plants.

Item Type: Article
Erschienen: 2004
Creators: Schaaf, Gabriel and Ludewig, Uwe and Erenoglu, Bülent E. and Mori, Satoshi and Kitahara, Takeshi and von Wirén, Nicolaus
Title: ZmYS1 functions as a proton-coupled symporter for phytosiderophore- and nicotianamine-chelated metals.
Language: English
Abstract:

Among higher plants graminaceous species have the unique ability to efficiently acquire iron from alkaline soils with low iron solubility by secreting phytosiderophores, which are hexadentate metal chelators with high affinity for Fe(III). Iron(III)-phytosiderophores are subsequently taken up by roots via YS1 transporters, that belong to the OPT oligopeptide transporter family. Despite its physiological importance at alkaline pH, uptake of Fe-phytosiderophores into roots of wild-type maize plants was greater at acidic pH and sensitive to the proton uncoupler CCCP. To access the mechanism of Fe-phytosiderophore acquisition, ZmYS1 was expressed in an iron uptake-defective yeast mutant and in Xenopus oocytes, where ZmYS1-dependent Fe-phytosiderophore transport was stimulated at acidic pH and sensitive to CCCP. Electrophysiological analysis in oocytes demonstrated that Fephytosiderophore transport depends on proton cotransport and on the membrane potential, which allows ZmYS1-mediated transport even at alkaline pH. We further investigated substrate specificity and observed that ZmYS1 complemented the growth defect of the zinc uptake-defective yeast mutant zap1 and transported various phytosiderophore-bound metals into oocytes, including zinc, copper, nickel, and, at a lower rate, also manganese and cadmium. Unexpectedly, ZmYS1 also transported Ni(II), Fe(II), and Fe(III) complexes with nicotianamine, a structural analog of phytosiderophores, which has been shown to act as an intracellular metal chelator in all higher plants. Our results show that ZmYS1 encodes a proton-coupled broad-range metal-phytosiderophore transporter that additionally transports Fe- and Ni-nicotianamine. These biochemical properties indicate a novel role of YS1 transporters for heavy metal homeostasis in plants.

Journal or Publication Title: The Journal of biological chemistry
Volume: 279
Number: 10
Divisions: 10 Department of Biology > Plant Nutrition and Biomass
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10 Department of Biology
Date Deposited: 16 Mar 2010 14:13
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