title: The phytochelatin transporters AtABCC1 and AtABCC2 mediate tolerance to cadmium and mercury.
abstract: Heavy metals such as cadmium (Cd) and mercury (Hg) are toxic pollutants that are detrimental to living organisms. Plants employ a two-step mechanism to detoxify toxic ions. First, phytochelatins bind to the toxic ion, and then the metal-phytochelatin complex is sequestered in the vacuole. Two ABCC-type transporters, AtABCC1 and AtABCC2, that play a key role in arsenic detoxification, have recently been identified in Arabidopsis thaliana. However, it is unclear whether these transporters are also implicated in phytochelatin-dependent detoxification of other heavy metals such as Cd(II) and Hg(II). Here, we show that atabcc1 single or atabcc1 atabcc2 double knockout mutants exhibit a hypersensitive phenotype in the presence of Cd(II) and Hg(II). Microscopic analysis using a Cd-sensitive probe revealed that Cd is mostly located in the cytosol of protoplasts of the double mutant, whereas it occurs mainly in the vacuole of wild-type cells. This suggests that the two ABCC transporters are important for vacuolar sequestration of Cd. Heterologous expression of the transporters in Saccharomyces cerevisiae confirmed their role in heavy metal tolerance. Over-expression of AtABCC1 in Arabidopsis resulted in enhanced Cd(II) tolerance and accumulation. Together, these results demonstrate that AtABCC1 and AtABCC2 are important vacuolar transporters that confer tolerance to cadmium and mercury, in addition to their role in arsenic detoxification. These transporters provide useful tools for genetic engineering of plants with enhanced metal tolerance and accumulation, which are desirable characteristics for phytoremediation.
authors.affiliation: Pohang University of Science and Technology-University of Zurich Cooperative Laboratory, Department of Integrative Bioscience and Biotechnology, World Class University Program, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Jiyoung
authors.initials: J
authors.lastname: Park
authors.forename: Won-Yong
authors.initials: WY
authors.lastname: Song
authors.forename: Donghwi
authors.initials: D
authors.lastname: Ko
authors.forename: Yujin
authors.initials: Y
authors.lastname: Eom
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Hansen
authors.forename: Michaela
authors.initials: M
authors.lastname: Schiller
authors.forename: Tai Gyu
authors.initials: TG
authors.lastname: Lee
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Youngsook
authors.initials: Y
authors.lastname: Lee
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001692:Biological Transport / Q000502:physiology; D002104:Cadmium / Q000378:metabolism*; D015870:Gene Expression; D055786:Gene Knockout Techniques; D008628:Mercury / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D054811:Phytochelatins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011523:Protoplasts; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology; D014617:Vacuoles / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; C495596:MRP1 protein, Arabidopsis; C495597:MRP2 protein, Arabidopsis; D002104:Cadmium; D054811:Phytochelatins; D008628:Mercury