title: Cadmium-inducible expression of the ABC-type transporter AtABCC3 increases phytochelatin-mediated cadmium tolerance in Arabidopsis.
abstract: The heavy metal cadmium (Cd) is a widespread environmental contaminant with harmful effects on living cells. In plants, phytochelatin (PC)-dependent Cd detoxification requires that PC-Cd complexes are transported into vacuoles. Here, it is shown that Arabidopsis thaliana seedlings defective in the ABCC transporter AtABCC3 (abcc3) have an increased sensitivity to different Cd concentrations, and that seedlings overexpressing AtABCC3 (AtABCC3ox) have an increased Cd tolerance. The cellular distribution of Cd was analysed in protoplasts from abcc3 mutants and AtABCC3 overexpressors grown in the presence of Cd, by means of the Cd-specific fluorochromes 5-nitrobenzothiazole coumarin (BTC-5N) and Leadmium™ Green AM dye. This analysis revealed that Cd is mostly localized in the cytosol of abcc3 mutant protoplasts whereas there is an increase in vacuolar Cd in protoplasts from AtABCC3ox plants. Overexpression of AtABCC3 in cad1-3 mutant seedlings defective in PC production and in plants treated with l-buthionine sulphoximine (BSO), an inhibitor of PC biosynthesis, had no effect on Cd tolerance, suggesting that AtABCC3 acts via PCs. In addition, overexpression of AtABCC3 in atabcc1 atabcc2 mutant seedlings defective in the Cd transporters AtABCC1 and AtABCC2 complements the Cd sensitivity of double mutants, but not in the presence of BSO. Accordingly, the level of AtABCC3 transcript in wild type seedlings was lower than that of AtABCC1 and AtABCC2 in the absence of Cd but higher after Cd exposure, and even higher in atabcc1 atabcc2 mutants. The results point to AtABCC3 as a transporter of PC-Cd complexes, and suggest that its activity is regulated by Cd and is co-ordinated with the activity of AtABCC1/AtABCC2.
authors.affiliation: Istituto di Biologia e Patologia Molecolari, CNR, Sapienza Università di Roma, Rome, Italy Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Brunetti
authors.affiliation: Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Rome, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Zanella
authors.affiliation: Istituto di Scienze delle Produzioni Alimentari, CNR, Lecce, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: De Paolis
authors.affiliation: Istituto di Biologia e Patologia Molecolari, CNR, Sapienza Università di Roma, Rome, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Di Litta
authors.affiliation: Istituto di Biologia e Patologia Molecolari, CNR, Sapienza Università di Roma, Rome, Italy Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Cecchetti
authors.affiliation: Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Rome, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Falasca
authors.affiliation: Dipartimento di Scienze della Terra, Sapienza Università di Roma, Rome, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Barbieri
authors.affiliation: Dipartimento di Biologia Ambientale, Sapienza Università di Roma, Rome, Italy.
authors.forename: Maria Maddalena
authors.initials: MM
authors.lastname: Altamura
authors.affiliation: Istituto di Biologia e Patologia Molecolari, CNR, Sapienza Università di Roma, Rome, Italy Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Costantino
authors.affiliation: Istituto di Biologia e Patologia Molecolari, CNR, Sapienza Università di Roma, Rome, Italy maura.cardarelli@uniroma1.it.
authors.forename: Maura
authors.initials: M
authors.lastname: Cardarelli
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000222:Adaptation, Physiological / Q000187:drug effects*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002104:Cadmium / Q000633:toxicity*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D054811:Phytochelatins / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D030821:Plants, Genetically Modified; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism
chemical_list: C000606110:ABCC3 protein, Arabidopsis; D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D002104:Cadmium; D019328:Buthionine Sulfoximine; D054811:Phytochelatins
keywords: ABC-type transporters; Arabidopsis; cadmium stress; cadmium tolerance; phytochelatins; vacuolar compartmentalization.