A secretory pathway-localized cation diffusion facilitator confers plant manganese tolerance.
Manganese toxicity is a major problem for plant growth in acidic soils, but cellular mechanisms that facilitate growth in such conditions have not been clearly delineated. Established mechanisms that counter metal toxicity in plants involve chelation and cytoplasmic export of the metal across the plasma or vacuolar membranes out of the cell or sequestered into a large organelle, respectively. We report here that expression of the Arabidopsis and poplar MTP11 cation diffusion facilitators in a manganese-hypersensitive yeast mutant restores manganese tolerance to wild-type levels. Microsomes from yeast expressing AtMTP11 exhibit enhanced manganese uptake. In accord with a presumed function of MTP11 in manganese tolerance, Arabidopsis mtp11 mutants are hypersensitive to elevated levels of manganese, whereas plants overexpressing MTP11 are hypertolerant. In contrast, sensitivity to manganese deficiency is slightly decreased in mutants and increased in overexpressing lines. Promoter-GUS studies showed that AtMTP11 is most highly expressed in root tips, shoot margins, and hydathodes, but not in epidermal cells and trichomes, which are generally associated with manganese accumulation. Surprisingly, imaging of MTP11-EYFP fusions demonstrated that MTP11 localizes neither to the plasma membrane nor to the vacuole, but to a punctate endomembrane compartment that largely coincides with the distribution of the trans-Golgi marker sialyl transferase. Golgi-based manganese accumulation might therefore result in manganese tolerance through vesicular trafficking and exocytosis. In accord with this proposal, Arabidopsis mtp11 mutants exhibit enhanced manganese concentrations in shoots and roots. We propose that Golgi-mediated exocytosis comprises a conserved mechanism for heavy metal tolerance in plants.
Peiter
Edgar
E
Department of Biology, University of York, PO Box 373, York YO10 5YW, United Kingdom.
Montanini
Barbara
B
Gobert
Anthony
A
Pedas
Pai
P
Husted
Søren
S
Maathuis
Frans J M
FJ
Blaudez
Damien
D
Chalot
Michel
M
Sanders
Dale
D
D000222:Adaptation, Physiological / Q000187:drug effects*; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D004058:Diffusion / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D017343:Genes, Plant; D005816:Genetic Complementation Test; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D008345:Manganese / Q000172:deficiency / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D032107:Populus / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects
D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; C520742:Mtp11 protein, Arabidopsis; D008345:Manganese