JXB Advance Access published online on February 2, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp007
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© 2009 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
Increased sensitivity to iron deficiency in Arabidopsis thaliana overaccumulating nicotianamine
Biochimie et Physiologie Moléculaire des Plantes. Centre National de la Recherche Scientifique (UMR 5004), Institut National de la Recherche Agronomique, Université Montpellier 2, École Nationale Supérieure d'Agronomie, 2 Place Viala, F-34060 Montpellier cedex 2, France
* To whom correspondence should be addressed. E-mail: czernic{at}univ-montp2.fr
Nicotianamine (NA) is a non-protein amino acid derivative synthesized from S-adenosyl L-methionine able to bind several metal ions such as iron, copper, manganese, zinc, or nickel. In plants, NA appears to be involved in iron availability and is essential for the plant to complete its biological cycle. In graminaceous plants, NA is also the precursor in the biosynthesis of phytosiderophores. Arabidopsis lines accumulating 4- and 100-fold more NA than wild-type plants were used in order to evaluate the impact of such an NA overaccumulation on iron homeostasis. The expression of iron-regulated genes including the IRT1/FRO2 iron uptake system is highly induced at the transcript level under both iron-sufficient and iron-deficient conditions. Nevertheless, NA overaccumulation does not interfere with the iron uptake mechanisms since the iron levels are similar in the NA-overaccumulating line and wild-type plants in both roots and leaves under both sufficient and deficient conditions. This observation also suggests that the translocation of iron from the root to the shoot is not affected in the NA-overaccumulating line. However, NA overaccumulation triggers an enhanced sensitivity to iron starvation, associated with a decrease in iron availability. This study draws attention to a particular phenotype where NA in excess paradoxically leads to iron deficiency, probably because of an increase of the NA apoplastic pool sequestering iron. This finding strengthens the notion that extracellular NA in the apoplast could be a major checkpoint to control plant iron homeostasis.
Key words: Apoplast, iron homeostasis, nicotianamine
Received 14 November 2008; Revised 19 December 2008 Accepted 22 December 2008
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