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A putative function of the Arabidopsis Fe-phytosiderophore transporter homolog AtYSL2 in Fe and Zn homeostasis

Abstract : 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::b-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::b-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 pecificity are likely to differ between AtYSL2 and ZmYS1.
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Submitted on : Sunday, December 20, 2020 - 2:12:17 PM
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Schaaf G.-et al-PlantCelPhysio...
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G. Schaff, A. Schikora, J. Häberle, Grégory Vert, U. Ludewig, et al.. A putative function of the Arabidopsis Fe-phytosiderophore transporter homolog AtYSL2 in Fe and Zn homeostasis. Plant and Cell Physiology, Oxford University Press (OUP), 2005, 46, pp.762-774. ⟨10.1093/pcp/pci081⟩. ⟨hal-00086935⟩



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