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: Hélène Molins, Laure Michelet, Viviane Lanquar, Astrid Agorio, Jérôme Giraudat, Thomas Roach, Anja Krieger-Liszkay, Sébastien Thomine
• Journal: Plant, cell & environment (Plant Cell Environ) Vol. 36 Issue 4 Pg. 804-17 (Apr 2013) ISSN: 1365-3040 [Electronic] United States
• PMID: 22998565 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2012 Blackwell Publishing Ltd.

Chemical References

• Antioxidants
• Arabidopsis Proteins
• Cation Transport Proteins
• NRAMP4 protein, Arabidopsis
• Nramp3 protein, Arabidopsis
• Cadmium
• Chlorophyll
• Aminoacyltransferases
• AT5G44070 protein, Arabidopsis

Topics

• Aminoacyltransferases (genetics, metabolism)
• Antioxidants (metabolism, pharmacology)
• Arabidopsis (drug effects, enzymology, genetics, physiology)
• Arabidopsis Proteins (genetics, metabolism)
• Biological Transport
• Cadmium (metabolism, toxicity)
• Cation Transport Proteins (genetics, metabolism)
• Chlorophyll (metabolism)
• Chloroplasts (metabolism)
• Gene Expression Regulation, Plant
• Homeostasis
• Mutation
• Oxidative Stress
• Plant Leaves (drug effects, enzymology, genetics, physiology)
• Plant Roots (drug effects, enzymology, genetics, physiology)
• Plant Shoots (drug effects, enzymology, genetics, physiology)
• Seedlings (drug effects, enzymology, genetics, physiology)
• Up-Regulation
• Vacuoles (metabolism)