, Volume 256, Issue 1, pp 161–170 | Cite as

Copper uptake mechanism of Arabidopsis thaliana high-affinity COPT transporters

  • Amparo SanzEmail author
  • Sharon Pike
  • Mather A Khan
  • Àngela Carrió-Seguí
  • David G Mendoza-Cózatl
  • Lola Peñarrubia
  • Walter Gassmann
Original Article


Copper (Cu) is an essential plant micronutrient. Under scarcity, Cu2+ is reduced to Cu+ and taken up through specific high-affinity transporters (COPTs). In Arabidopsis, the COPT family consists of six members, either located at the plasma membrane (COPT1, COPT2, and COPT6) or in internal membranes (COPT3 and COPT5). Cu uptake by COPT proteins has been mainly assessed through complementation studies in corresponding yeast mutants, but the mechanism of this transport has not been elucidated. To test whether Cu is incorporated by an electrogenic mechanism, electrophysiological changes induced by Cu addition were studied in Arabidopsis thaliana. Mutant (T-DNA insertion mutants, copt2–1 and copt5–2) and overexpressing lines (COPT1OE and COPT5OE) with altered expression of COPT transporters were compared to wild-type plants. No significant changes of the membrane potential (Em) were detected, regardless of genotype or Cu concentration supplied. In contrast, membrane depolarization was detected in response to iron supply in both wild-type and in mutant or transgenic plants. Similar results were obtained for trans-plant potentials (TPP). GFP fusions of the plasma membrane COPT2 and the internal COPT5 transporters were expressed in Xenopus laevis oocytes to potentiate Cu uptake signals, and the cRNA-injected oocytes were tested for electrical currents upon Cu addition using two-electrode voltage clamp. Results with oocytes confirmed those obtained in plants. Cu accumulation in injected oocytes was measured by ICP-OES, and a significant increase in Cu content with respect to controls occurred in oocytes expressing COPT2:GFP. The possible mechanisms driving this transport are discussed in this manuscript.


Arabidopsis thaliana Copper uptake COPT transporters Membrane (Em) and trans-plant (TPP) potentials Two-electrode voltage clamp (TEVC) Xenopus laevis oocytes 



This work was performed during a sabbatical leave of AS at the University of Missouri-Columbia. AC-S is recipient of a pre-doctoral fellowship from the Spanish Ministry of Economy, Industry, and Competitiveness. Elemental analyses at UM-C were supported by a US National Science Foundation award (IOS-1252706 to DM-C). We thank the skillful technical help of Li Na Nguyen, Conner Rogan, and Chris Garner (UM-C).


Travel expenses were financed by the University of Valencia (UV-INV-EPD116-383019) and supported by grants BIO2014-56298-P and BIO2017-87828-C2-1-P (to LP and AS) from the Spanish Ministry of Economy and Competitiveness and FEDER funds from the European Union.

Compliance with ethical standards

Conflict of interests

The authors declare that they have no conflict of interests.

Supplementary material

709_2018_1286_MOESM1_ESM.docx (147 kb)
Figure S1 TPP variations in Arabidopsis thaliana WT plants in response to light conditions and induced by addition of 5 mM glucose (Glu) to the medium bathing the roots. Light/dark (L/D) or dark/light (D/L) transitions were applied as indicated in the graph. Numbers in brackets show voltages in mV. (DOCX 146 kb)
709_2018_1286_MOESM2_ESM.docx (1.1 mb)
Figure S2 Confocal images of X. laevis COPT2:GFP (a, c) and COPT5:GFP (b, d) cRNA-injected oocytes showing membrane localization of the green fluorescent signal of GFP (40X magnification). Images were taken 24 h after injection. (DOCX 1129 kb)


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Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Dpt de Biologia VegetalUniversitat de ValènciaValenciaSpain
  2. 2.Division of Plant Sciences, CS Bond Life Sciences Center, and Interdisciplinary Plant GroupUniversity of MissouriColumbiaUSA
  3. 3.Dpt de Bioquímica i Biologia Molecular and ERI BiotecmedUniversitat de ValènciaValenciaSpain

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