title: HMA P-type ATPases are the major mechanism for root-to-shoot Cd translocation in Arabidopsis thaliana.
abstract: The Zn/Cd-transporting ATPases, HMA2 and HMA4, essential for root-to-shoot Zn translocation, are also able to transport Cd. Phytochelatins (PCs) are a major mechanism of Cd detoxification through the sequestration of PC-Cd complexes in vacuoles. The roles of HMA2 and HMA4 in root-to-shoot Cd translocation and Cd tolerance were investigated in the PC-deficient, cad1-3 mutant and CAD1 backgrounds. Six lines, with all possible combinations of hma2, hma4 and cad1 mutations, were constructed. The lines were tested for Cd-sensitivity on agar medium, and radioactive (109)Cd was used to measure Cd uptake and translocation from root to shoot over periods of up to 6 d. In hma4 and hma2,hma4, but not hma2, root-to-shoot Cd translocation was decreased to about 60 and 2%, respectively, of that in the wild-type. Cd sensitivity increased approximately twofold in the hma2,hma4 mutant in both CAD1 and cad1 backgrounds. PC deficiency resulted in an increase in shoot Cd concentrations. The near-complete abolition of root-to-shoot Cd translocation resulting from the loss of function of HMA2 and HMA4 demonstrates they are the major mechanism for Cd translocation in Arabidopsis thaliana.
authors.affiliation: Department of Genetics, The University of Melbourne, Parkville, Australia, 3010.
authors.forename: Chong Kum Edwin
authors.initials: CKE
authors.lastname: Wong
authors.affiliation: Department of Genetics, The University of Melbourne, Parkville, Australia, 3010.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Cobbett
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002104:Cadmium / Q000493:pharmacokinetics*; D005838:Genotype; D054811:Phytochelatins / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002104:Cadmium; D054811:Phytochelatins; D000251:Adenosine Triphosphatases; C494967:HMA2 protein, Arabidopsis; C477864:HMA4 protein, Arabidopsis