Cucumber metal tolerance protein CsMTP9 is a plasma membrane H⁺-coupled antiporter involved in the Mn²⁺ and Cd²⁺ efflux from root cells.
Members of the plant metal tolerance protein (MTP) family have been classified into three major groups - Zn-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 μm and 2.5 μm 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.
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.
Magdalena
M
Migocka
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.
Anna
A
Papierniak
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.|Department of Animal Developmental Biology, Wroclaw University, Institute of Experimental Biology, Sienkiewicza 21, Wroclaw, 50-335, Poland.
Anna
A
Kosieradzka
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.|Department of Animal Developmental Biology, Wroclaw University, Institute of Experimental Biology, Sienkiewicza 21, Wroclaw, 50-335, Poland.
Ewelina
E
Posyniak
Department of Genetics and Cell Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.
Ewa
E
Maciaszczyk-Dziubinska
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.
Robert
R
Biskup
Department of Animal Developmental Biology, Wroclaw University, Institute of Experimental Biology, Sienkiewicza 21, Wroclaw, 50-335, Poland.
Arnold
A
Garbiec
Department of Plant Molecular Physiology, Wroclaw University, Institute of Experimental Biology, Kanonia 6/8, Wroclaw, 50-328, Poland.
Tadeusz
T
Marchewka
D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002104:Cadmium / Q000378:metabolism* / Q000633:toxicity; D002462:Cell Membrane; D018553:Cucumis sativus / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008345:Manganese / Q000378:metabolism* / Q000633:toxicity; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D012440:Saccharomyces / Q000378:metabolism
D017920:Antiporters; D010940:Plant Proteins; D002104:Cadmium; D008345:Manganese
CDF (cation diffusion facilitator) family; Cucumis sativus; MTP (metal tolerance protein) family; heavy metals; metal homeostasis; tonoplast