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Identification of mutations allowing Natural Resistance Associated Macrophage Proteins (NRAMP) to discriminate against cadmium
Author(s) -
Pottier Mathieu,
Oomen Ronald,
Picco Cristiana,
Giraudat Jérôme,
ScholzStarke Joachim,
Richaud Pierre,
Carpaneto Armando,
Thomine Sébastien
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12914
Subject(s) - transporter , population , yeast , biology , mutation , biochemistry , gene , xenopus , chemistry , cadmium , divalent , genetics , organic chemistry , demography , sociology
Summary Each essential transition metal plays a specific role in metabolic processes and has to be selectively transported. Living organisms need to discriminate between essential and non‐essential metals such as cadmium (Cd 2+ ), which is highly toxic. However, transporters of the natural resistance‐associated macrophage protein ( NRAMP ) family, which are involved in metal uptake and homeostasis, generally display poor selectivity towards divalent metal cations. In the present study we used a unique combination of yeast‐based selection, electrophysiology on Xenopus oocytes and plant phenotyping to identify and characterize mutations that allow plant and mammalian NRAMP transporters to discriminate between their metal substrates. We took advantage of the increased Cd 2+ sensitivity of yeast expressing At NRAMP 4 to select mutations that decrease Cd 2+ sensitivity while maintaining the ability of At NRAMP 4 to transport Fe 2+ in a population of randomly mutagenized At NRAMP 4 cDNA s. The selection identified mutations in three residues. Among the selected mutations, several affect Zn 2+ transport, whereas only one, E401K, impairs Mn 2+ transport by At NRAMP 4. Introduction of the mutation F413I, located in a highly conserved domain, into the mammalian DMT 1 transporter indicated that the importance of this residue in metal selectivity is conserved among NRAMP transporters from plant and animal kingdoms. Analyses of overexpressing plants showed that At NRAMP 4 affects the accumulation of metals in roots. Interestingly, the mutations selectively modify Cd 2+ and Zn 2+ accumulation without affecting Fe transport mediated by NRAMP 4 in planta . This knowledge may be applicable for limiting Cd 2+ transport by other NRAMP transporters from animals or plants.