The Arabidopsis metal tolerance protein AtMTP3 maintains metal homeostasis by mediating Zn exclusion from the shoot under Fe deficiency and Zn oversupply.
Zinc ions are required to maintain the biological activity of numerous proteins. However, when mislocalized or accumulated in excess, Zn(2+) ions are toxic because of adventitious binding to proteins and displacement of other metal ions, among them Fe(2+), from their binding sites. Heterologous expression of a previously uncharacterized Arabidopsis thaliana metal tolerance protein, MTP3, in the zrc1 cot1 mutant of budding yeast restores tolerance to, and cellular accumulation of, zinc and cobalt. An MTP3-GFP fusion protein localizes to the vacuolar membrane when expressed in Arabidopsis. Ectopic over-expression of MTP3 increases Zn accumulation in both roots and rosette leaves of A. thaliana, and enhances Zn tolerance. Exposure of wild-type plants to high but non-toxic concentrations of Zn or Co, or Fe deficiency, strongly induce MTP3 expression specifically in epidermal and cortex cells of the root hair zone. Silencing of MTP3 by RNA interference causes Zn hypersensitivity and enhances Zn accumulation in above-ground organs of soil-grown plants and of seedlings exposed to excess Zn or to Fe deficiency. Our data indicate that, in wild-type A. thaliana, the AtMTP3 protein contributes to basic cellular Zn tolerance and controls Zn partitioning, particularly under conditions of high rates of Zn influx into the root symplasm.
Arrivault
Stéphanie
S
Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany.
Senger
Toralf
T
Krämer
Ute
U
D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D027682:Cation Transport Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D003035:Cobalt / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000032:analysis; D006706:Homeostasis; D007425:Intracellular Membranes / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D008954:Models, Biological; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000032:analysis; D014617:Vacuoles / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; C512224:MTP3 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D003035:Cobalt; D007501:Iron; D015032:Zinc