title: Zinc transporter of Arabidopsis thaliana AtMTP1 is localized to vacuolar membranes and implicated in zinc homeostasis.
abstract: Cation diffusion facilitator (CDF) proteins belong to a family of heavy metal efflux transporters that might play an essential role in homeostasis and tolerance to metal ions. We investigated the subcellular localization of Arabidopsis thaliana AtMTP1, a member of the CDF family, and its physiological role in the tolerance to Zn using MTP1-deficient mutant plants. AtMTP1 was immunochemically detected as a 43 kDa protein in the vacuolar membrane fractioned by sucrose density gradient centrifugation. The expression level of AtMTP1 in suspension-cultured cells was not affected by the Zn concentration in the medium. When AtMTP1 fused with green fluorescent protein was transiently expressed in protoplasts prepared from Arabidopsis suspension-cultured cells, green fluorescence was clearly observed in the vacuolar membrane. A T-DNA insertion mutant line for AtMTP1 displays enhanced sensitivity to high Zn concentrations ranging from 200 to 500 microM, but not to Zn-deficient conditions. Mesophyll cells of the mtp1-1 mutant plants grown in the presence of 500 microM Zn were degraded, suggesting that Zn at high concentrations causes serious damage to leaves and that AtMTP1 plays a crucial role in preventing this damage in plants. Thus we propose that AtMTP1 is localized in the vacuolar membrane and is involved in sequestration of excess Zn in the cytoplasm into vacuoles to maintain Zn homeostasis.
authors.affiliation: Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobae
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Uemura
authors.forename: Masa H
authors.initials: MH
authors.lastname: Sato
authors.forename: Miwa
authors.initials: M
authors.lastname: Ohnishi
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Mimura
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000502:physiology; D049452:Green Fluorescent Proteins; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism* / Q000648:ultrastructure; D015032:Zinc / Q000378:metabolism* / Q000633:toxicity
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D027682:Cation Transport Proteins; D049452:Green Fluorescent Proteins; D011993:Recombinant Fusion Proteins; D015032:Zinc; C500829:ZAT protein, Arabidopsis