Journal Article

Zinc Transporter of <i>Arabidopsis thaliana</i> AtMTP1 is Localized to Vacuolar Membranes and Implicated in Zinc Homeostasis

Yoshihiro Kobae, Tomohiro Uemura, Masa H. Sato, Miwa Ohnishi, Tetsuro Mimura, Tsuyoshi Nakagawa and Masayoshi Maeshima

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 12, pages 1749-1758
Published in print December 2004 | ISSN: 0032-0781
Published online December 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pci015
Zinc Transporter of Arabidopsis thaliana AtMTP1 is Localized to Vacuolar Membranes and Implicated in Zinc Homeostasis

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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 µM, but not to Zn-deficient conditions. Mesophyll cells of the mtp1-1 mutant plants grown in the presence of 500 µM 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.

Keywords: Keywords: Arabidopsis — Cation diffusion facilitator — Metal ion homeostasis — Vacuolar membrane — Zinc transporter.; Abbreviations: AHA3, the third isoform of plasma membrane H+-ATPase; ER, endoplasmic reticulum; GFP, green fluorescent protein; MTP, metal-tolerant protein; VHA-a, subunit a of vacuolar membrane H+-ATPase; MES, 2-(N-morpholino) ethanesulfonate.

Journal Article.  6685 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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