Journal Article

A Putative Function for the <i>Arabidopsis</i> Fe–Phytosiderophore Transporter Homolog AtYSL2 in Fe and Zn Homeostasis

Gabriel Schaaf, Adam Schikora, Jennifer Häberle, Grégory Vert, Uwe Ludewig, Jean-François Briat, Catherine Curie and Nicolaus von Wirén

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 46, issue 5, pages 762-774
Published in print May 2005 | ISSN: 0032-0781
Published online May 2005 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pci081
A Putative Function for the Arabidopsis Fe–Phytosiderophore Transporter Homolog AtYSL2 in Fe and Zn Homeostasis

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Although Arabidopsis thaliana does not produce phytosiderophores (PS) under Fe deficiency, it contains eight homologs of the metal–PS/metal–nicotianamine (NA) transporter ZmYS1 from maize. This study aimed to investigate whether one of the closest Arabidopsis homologs to ZmYS1, AtYSL2, is involved in metal–chelate transport. Northern analysis revealed high expression levels of AtYSL2 in Fe-sufficient or Fe-resupplied roots, while under Fe deficiency transcript levels decreased. Quantitative real-time polymerase chain reaction (PCR) and analysis of transgenic plants expressing an AtYSL2 promoter::β-glucuronidase gene further allowed the detection of down-regulated AtYSL2 gene expression under Zn and Fe deficiency. In contrast to ZmYS1, AtYSL2 did not mediate metal–PS or metal–NA transport in yeast mutants defective in Cu or Fe uptake, nor did AtYSL2 mediate Fe(II)–NA-, Fe(III)–NA- or Ni(II)–NA-inducible currents when assayed by two-electrode voltage clamp in Xenopus oocytes. Moreover, truncation of the N-terminus to remove putative phosphorylation sites that might trigger autoinhibition did not confer functionality to AtYSL2. A direct growth comparison of yeast cells transformed with AtYSL2 in two different yeast expression vectors showed that transformation with empty pFL61 repressed growth even under non-limiting Fe supply. We therefore conclude that the yeast complementation assay previously employed does not allow the identification of AtYSL2 as an Fe–NA transporter. Transgenic plants expressing an AtYSL2 promoter::β-glucuronidase gene showed expression in root endodermis and pericycle cells facing the meta-xylem tubes. Taken together, our investigations support an involvement of AtYSL2 in Fe and Zn homeostasis, although functionality or substrate specificity are likely to differ between AtYSL2 and ZmYS1.

Keywords: nicotianamine; iron transport; strategy II; yeast complementation; Xenopus oocytes; DMA, 2′-deoxy-mugineic acid; GFP, green fluorescent protein; GUS, β-glucuronidase; NA, nicotianamine; NAAT, nicotianamine amino-transferase; NAS, nicotianamine synthase; ORF, open reading frame; PS, phytosiderophore; TMD, transmembrane-spanning domain

Journal Article.  9820 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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