S.C.G and A.A.F. contributed equally to this work.
Complexation of Hg with phytochelatins is important for plant Hg tolerance
Article first published online: 15 MAR 2011
© 2011 Blackwell Publishing Ltd
Plant, Cell & Environment
Volume 34, Issue 5, pages 778–791, May 2011
How to Cite
CARRASCO-GIL, S., ÁLVAREZ-FERNÁNDEZ, A., SOBRINO-PLATA, J., MILLÁN, R., CARPENA-RUIZ, R. O., LEDUC, D. L., ANDREWS, J. C., ABADÍA, J. and HERNÁNDEZ, L. E. (2011), Complexation of Hg with phytochelatins is important for plant Hg tolerance. Plant, Cell & Environment, 34: 778–791. doi: 10.1111/j.1365-3040.2011.02281.x
- Issue published online: 4 APR 2011
- Article first published online: 15 MAR 2011
- Accepted manuscript online: 28 JAN 2011 06:36AM EST
- Received 8 September 2010; received in revised form 4 December 2010; accepted for publication 21 December 2010
- mass spectrometry;
- soluble fraction;
- X-ray absorption spectroscopy
Three-week-old alfalfa (Medicago sativa), barley (Hordeum vulgare) and maize (Zea mays) were exposed for 7 d to 30 µm of mercury (HgCl2) to characterize the Hg speciation in root, with no symptoms of being poisoned. The largest pool (99%) was associated with the particulate fraction, whereas the soluble fraction (SF) accounted for a minor proportion (<1%). Liquid chromatography coupled with electro-spray/time of flight mass spectrometry showed that Hg was bound to an array of phytochelatins (PCs) in root SF, which was particularly varied in alfalfa (eight ligands and five stoichiometries), a species that also accumulated homophytochelatins. Spatial localization of Hg in alfalfa roots by microprobe synchrotron X-ray fluorescence spectroscopy showed that most of the Hg co-localized with sulphur in the vascular cylinder. Extended X-ray Absorption Fine Structure (EXAFS) fingerprint fitting revealed that Hg was bound in vivo to organic-S compounds, i.e. biomolecules containing cysteine. Albeit a minor proportion of total Hg, Hg–PCs complexes in the SF might be important for tolerance to Hg, as was found with Arabidopsis thaliana mutants cad2-1 (with low glutathione content) and cad1-3 (unable to synthesize PCs) in comparison with wild type plants. Interestingly, high-performance liquid chromatography-electrospray ionization-time of flight analysis showed that none of these mutants accumulated Hg–biothiol complexes.