title: Mutants impaired in vacuolar metal mobilization identify chloroplasts as a target for cadmium hypersensitivity in Arabidopsis thaliana.
abstract: Cadmium (Cd) is highly toxic to plants causing growth reduction and chlorosis. It binds thiols and competes with essential transition metals. It affects major biochemical processes such as photosynthesis and the redox balance, but the connection between cadmium effects at the biochemical level and its deleterious effect on growth has seldom been established. In this study, two Cd hypersensitive mutants, cad1-3 impaired in phytochelatin synthase (PCS1), and nramp3nramp4 impaired in release of vacuolar metal stores, have been compared. The analysis combines genetics with measurements of photosynthetic and antioxidant functions. Loss of AtNRAMP3 and AtNRAMP4 function or of PCS1 function leads to comparable Cd sensitivity. Root Cd hypersensitivities conferred by cad1-3 and nramp3nramp4 are cumulative. The two mutants contrast in their tolerance to oxidative stress. In nramp3nramp4, the photosynthetic apparatus is severely affected by Cd, whereas it is much less affected in cad1-3. In agreement with chloroplast being a prime target for Cd toxicity in nramp3nramp4, the Cd hypersensitivity of this mutant is alleviated in the dark. The Cd hypersensitivity of nramp3nramp4 mutant highlights the critical role of vacuolar metal stores to supply essential metals to plastids and maintain photosynthetic function under Cd and oxidative stresses.
authors.affiliation: Institut des Sciences du Végétal, CNRS, Gif-sur-Yvette 91198, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Molins
authors.forename: Laure
authors.initials: L
authors.lastname: Michelet
authors.forename: Viviane
authors.initials: V
authors.lastname: Lanquar
authors.forename: Astrid
authors.initials: A
authors.lastname: Agorio
authors.forename: Jérôme
authors.initials: J
authors.lastname: Giraudat
authors.forename: Thomas
authors.initials: T
authors.lastname: Roach
authors.forename: Anja
authors.initials: A
authors.lastname: Krieger-Liszkay
authors.forename: Sébastien
authors.initials: S
authors.lastname: Thomine
mesh_terms: D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D009154:Mutation; D018384:Oxidative Stress; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D027682:Cation Transport Proteins; C408073:NRAMP4 protein, Arabidopsis; C408072:Nramp3 protein, Arabidopsis; D002104:Cadmium; D002734:Chlorophyll; D019881:Aminoacyltransferases; C502365:AT5G44070 protein, Arabidopsis