Elevated nicotianamine levels in Arabidopsis halleri roots play a key role in zinc hyperaccumulation

Titelangaben

Deinlein, Ulrich ; Weber, Michael ; Schmidt, Holger ; Rensch, Stefan ; Trampczynska, Aleksandra ; Hansen, Thomas H. ; Husted, Søren ; Schjørring, Jan Kofod ; Talke, Ina N. ; Krämer, Ute ; Clemens, Stephan:
Elevated nicotianamine levels in Arabidopsis halleri roots play a key role in zinc hyperaccumulation.
In: The Plant Cell. Bd. 24 (2012) Heft 2 . - S. 708-723.
ISSN 1532-298X
DOI: https://doi.org/10.1105/tpc.111.095000

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Abstract

Zn deficiency is among the leading health risk factors in developing countries. Breeding of Zn-enriched crops is expected to be facilitated by molecular dissection of plant Zn hyperaccumulation (i.e., the ability of certain plants to accumulate Zn to levels >100-fold higher than normal plants). The model hyperaccumulators Arabidopsis halleri and Noccaea caerulescens share elevated nicotianamine synthase (NAS) expression relative to nonaccumulators among a core of alterations in metal homeostasis. Suppression of Ah-NAS2 by RNA interference (RNAi) resulted in strongly reduced root nicotianamine (NA) accumulation and a concomitant decrease in root-to-shoot translocation of Zn. Speciation analysis by size-exclusion chromatography coupled to inductively coupled plasma mass spectrometry showed that the dominating Zn ligands in roots were NA and thiols. In NAS2-RNAi plants, a marked increase in Zn-thiol species was observed. Wild-type A. halleri plants cultivated on their native soil showed elemental profiles very similar to those found in field samples. Leaf Zn concentrations in NAS2-RNAi lines, however, did not reach the Zn hyperaccumulation threshold. Leaf Cd accumulation was also significantly reduced. These results demonstrate a role for NAS2 in Zn hyperaccumulation also under near-natural conditions. We propose that NA forms complexes with Zn(II) in root cells and facilitates symplastic passage of Zn(II) toward the xylem.