title: The OsHMA2 transporter is involved in root-to-shoot translocation of Zn and Cd in rice.
abstract: Zinc (Zn) is an essential micronutrient for plants and humans. Cadmium (Cd) is a Zn analog and one of the most toxic heavy metals to humans. Here we investigated the role of the Zn/Cd transporter OsHMA2. OsHMA2:GFP fusion protein localized to the plasma membrane in onion epidermal cells. The yeast expressing OsHMA2 was able to reverse the growth defect in the presence of excess Zn. The expression of OsHMA2 in rice was observed mainly in the roots where OsHMA2 transcripts were abundant in vascular bundles. Furthermore, Zn and Cd concentrations of OsHMA2-suppressed rice decreased in the leaves, while the Zn concentration increased in the roots compared with the wild type (WT). These results suggest that OsHMA2 plays a role in Zn and Cd loading to the xylem and participates in root-to-shoot translocation of these metals in rice. Furthermore, the Cd concentration in the grains of OsHMA2-overexpressing rice as well as in OsSUT1-promoter OsHMA2 rice decreased to about half that of the WT, although the other metal concentrations were the same as in the WT. A phenotype that reduces only the Cd concentration in rice grains will be very useful for transgenic approaches to food safety.
authors.affiliation: Graduate School of Agricultural & Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Takahashi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishimaru
authors.forename: Hugo
authors.initials: H
authors.lastname: Shimo
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ogo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Senoura
authors.forename: Naoko K
authors.initials: NK
authors.lastname: Nishizawa
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakanishi
mesh_terms: D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000032:analysis; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis; D015032:Zinc / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D002104:Cadmium; D049452:Green Fluorescent Proteins; D015032:Zinc