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Angiosperm Flora of India

Complexation of Hg with phytochelatins is important for plant Hg tolerance

Publication Type:Journal Article
Year of Publication:2011
Authors:CARRASCO-GIL, SANDRA, ÁLVAREZ-FERNÁNDEZ, ANA, SOBRINO-PLATA, JUAN, MILLÁN, ROCÍO, CARPENA-RUIZ, RAMÓNO, LEDUC, DANIKAL, ANDREWS, JOYC, ABADÍA, JAVIER, HERNÁNDEZ, LUÍSE
Journal:Plant, Cell & Environment
Volume:34
Issue:5
Date Published:2011
ISBN Number:1365-3040
Keywords:biothiols, EXAFS, Hordeum, Hordeum vulgare, mass spectrometry, Medicago, mercury, phytochelatins, soluble fraction, X-ray absorption spectroscopy
Abstract:

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.

URL:http://dx.doi.org/10.1111/j.1365-3040.2011.02281.x
Short Title:Plant, Cell & Environment
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