Retracted: Cucumber metal tolerance protein CsMTP9 is a plasma membrane H⁺‐coupled antiporter involved in the Mn²⁺ and Cd²⁺ efflux from root cells

Abstract

These authors contributed equally to this work. SUMMARYMembers of the plant metal tolerance protein (MTP) family have been classified into three major groupsZn-CDF, Mn-CDF and Zn/Fe-CDF -however, the selectivity of most of the MTPs has not been confirmed yet. Cucumber gene CsMTP9 encoding a putative CDF transporter homologous to members of the Mn-CDF cluster is expressed exclusively in roots. The relative abundance of CsMTP9 transcript and protein in roots is significantly increased under Mn excess and Cd. Immunolocalization with specific antibodies revealed that CsMTP9 is a plasma membrane transporter that localizes to the inner PM domain of root endodermal cells. The plasma membrane localization of CsMTP9 was confirmed by the expression of the fusion proteins of GFP (green fluorescent protein) and CsMTP9 in yeast and protoplasts prepared from Arabidopsis cells. In yeast, CsMTP9 transports Mn 2+ and Cd 2+ via a proton-antiport mechanism with an apparent Km values of approximately 10 lM and 2.5 lM for Mn 2+ and Cd 2+ , respectively. In addition, CsMTP9 expression in yeast rescues the Mn-and Cd-hypersensitive phenotypes through the enhanced efflux of Mn 2+ and Cd 2+ from yeast cells. Similarly, the overexpression of CsMTP9 in A. thaliana confers increased resistance of plants to Mn excess and Cd but not to other heavy metals and leads to the enhanced translocation of manganese and cadmium from roots to shoots. These findings indicate that CsMTP9 is a plasma membrane H + -coupled Mn 2+ and Cd 2+ antiporter involved in the efflux of manganese and cadmium from cucumber root cells by the transport of both metals from endodermis into vascular cylinder.

Retracted: Cucumber metal tolerance protein 7 (CsMTP7) is involved in the accumulation of Fe in mitochondria under Fe excess

“…As plant MTP7 proteins have been classified as putative Fe/Zn transporters (Gustin et al ., ), we assumed that the CsMTP7 transcripts could be affected by changes in cellular Fe or Zn homeostasis. To test this hypothesis, we analyzed the levels of sCsMTP7 and lCsMTP7 transcripts in the roots of cucumbers grown under different Fe and Zn availability as well as under the excess of other heavy metals, such as Mn, Ni, Co or Cd, which also serve as substrates of plant MTP transporters (Persans et al ., ; Delhaize et al ., , ; Arrivault et al ., ; Peiter et al ., ; Yuan et al ., ; Menguer et al ., ; Migocka et al ., , ,b; Pedas et al ., ). As shown in Figure (b), the sCsMTP7 mRNA/ lCsMTP7 mRNA ratio was significantly altered depending on the external Fe level.…”

“…The CDF proteins so far characterized in plants localize to the tonoplast (MTP1, MTP3, MTP4 and MTP8) (Delhaize et al ., ; Desbrosses‐Fonrouge et al ., ; Arrivault et al ., ; Migocka et al ., , 2015a), the Golgi/prevacuolar system (MTP11, MTP8, MTP5 and MTP12) (Delhaize et al ., ; Peiter et al ., ; Pedas et al ., ) or the plasma membrane (MTP9) (Migocka et al ., 2015b; Ueno et al ., ) and contribute to the efflux of a wide range of heavy metals, including Zn, Cd and Mn, out of the cytoplasm. CsMTP7 localizes to the mitochondria of plant and yeast cells, consistent with the presence of the putative mitochondrial targeting sequence within the N‐terminal domain of the cucumber protein.…”

“…Therefore, we believe that CsMTP7 display low affinity to the transported metal – Fe and thus, is activated by the high intracellular Fe concentrations. Similarly, all the other so far characterized plant MTP proteins (MTP1, MTP4, MTP8 and MTP9) also display low affinity to their metal substrates (Kawachi et al ., ; Migocka et al ., , ,b), suggesting that the function of plant MTPs is related to the transport of surplus metals from the cytosol into the other compartments for cellular detoxification or the storage of essential metals, such as Zn and Fe.…”

Hydrogen sulfide - cysteine cycle system enhances cadmium tolerance through alleviating cadmium-induced oxidative stress and ion toxicity in Arabidopsis roots

“…Malondialdehyde (MDA), one of the decomposition products of lipid peroxidation, can modify active substrates in plant cells, including nucleic acids, proteins and saccharides11. To become resistant to Cd 2+ toxicity, plants have developed several strategies, such as inducing the alternative respiratory pathway11, activating antioxidants and glutathione (GSH)12, and regulating the influx and efflux of heavy metals1314, as well as regulating the levels of heavy metal chelators, phytochelatins (PCs)15 and metallothioneins (MTs)16.…”

Metal transport protein 8 in Camellia sinensis confers superior manganese tolerance when expressed in yeast and Arabidopsis thaliana

“…Migocka and his colleagues reported that the vacuolar membrane localized cucumber-MTP8, a Mn transporter, which helps maintain Mn homeostasis in root cells18. The same group also found that CsMTP9 is a plasma membrane H + -coupled Mn 2+ and Cd 2+ antiporter involved in the efflux of Mn and Cd from cucumber root cells by transporting both metals from the endodermis into vascular tissues36. Golgi localized Mn 2+ transport proteins, MTP8.1 and MTP8.2, are involved in barley intracellular Mn homeostasis37.…”