Mercury localization and speciation in plants grown hydroponically or in a natural environment.

Better understanding of mercury (Hg) accumulation, distribution, and speciation in plants is required to evaluate potential risks for the environment and to optimize phytostabilization strategies for Hg-contaminated soils. The behavior of Hg in alfalfa (Medicago sativa) plants grown under controlled conditions in a hydroponic system (30 μM HgCl2) was compared with that of naturally occurring Horehound (Marrubium vulgare) plants collected from a mining soil polluted with Hg (Almadenejos, Spain) to characterize common mechanisms of tolerance. Synchrotron X-ray Fluorescence microprobe (μ-SXRF) showed that Hg accumulated at the root apex of alfalfa and was distributed through the vascular system to the leaves.

Imaging translocation and transformation of bioavailable selenium by Stanleya pinnata with X-ray microscopy.

Selenium hyperaccumulator Stanleya pinnata, Colorado ecotype, was supplied with water-soluble and biologically available selenate or selenite. Selenium distribution and tissue speciation were established using X-ray microscopy (micro-X-ray fluorescence and transmission X-ray microscopy) in two dimensions and three dimensions. The results indicate that S.

Complexation of Hg with phytochelatins is important for plant Hg tolerance.

Three-week-old alfalfa (Medicago sativa), barley (Hordeum vulgare) and maize (Zea mays) were exposed for 7 d to 30 µm of mercury (HgCl(2) ) 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.

Phytoremediation of selenium using transgenic plants.

Selenium (Se) is a micronutrient for many organisms but also toxic at higher concentrations. Both selenium deficiency and toxicity are serious problems worldwide. Owing to the similarity of selenium to sulfur, plants readily take up and assimilate selenate via sulfur transporters and enzymes and can even volatilize selenium.

Selenium volatiles as proxy to the metabolic pathways of selenium in genetically modified Brassica juncea.

In this study we demonstrate that the headspace selenium volatiles could be used as proxy to the metabolic pathways in the Se-accumulator plant Brassica juncea. The selenium metabolic pathways in wild type plants are compared to those of several genetically modified cultures. Complementary use of atomic and molecular mass spectrometric techniques also allowed for identification of yet unreported minor headspace Se-containing volatiles such as CH3SeSeSeCH3, CH3SeSSeCH3, and CH3SeCH2CH3.

Transgenic Indian mustard overexpressing selenocysteine lyase or selenocysteine methyltransferase exhibit enhanced potential for selenium phytoremediation under field conditions.

Two new transgenic Indian mustard [Brassica juncea (L.) Czern.] lines were tested under field conditions for their ability to accumulate selenium (Se)from Se- and boron-contaminated saline sediment.

Overexpressing both ATP sulfurylase and selenocysteine methyltransferase enhances selenium phytoremediation traits in Indian mustard.

A major goal of our selenium (Se) phytoremediation research is to use genetic engineering to develop fast-growing plants with an increased ability to tolerate, accumulate, and volatilize Se. To this end we incorporated a gene (encoding selenocysteine methyltransferase, SMT) from the Se hyperaccumulator, Astragalus bisulcatus, into Indian mustard (LeDuc, D.L.

Study of phytochelatins and other related thiols as complexing biomolecules of As and Cd in wild type and genetically modified Brassica juncea plants.

The accumulation of As and Cd in Brassica juncea plants and the formation of complexes of these elements with bioligands such as glutathione and/or phytochelatins (PCs) is studied. The genetic manipulation of these plants to induce higher As and Cd accumulation has been achieved by overexpressing the genes encoding for gamma-glutamyl cysteine synthetase (gamma-ECS) and glutathione synthetase (GS). These two enzymes are responsible for glutathione (GSH) formation in plants, which is the first step in the production of PCs.

Phytoremediation of toxic trace elements in soil and water.

Toxic heavy metals and metalloids, such as cadmium, lead, mercury, arsenic, and selenium, are constantly released into the environment. There is an urgent need to develop low-cost, effective, and sustainable methods for their removal or detoxification. Plant-based approaches, such as phytoremediation, are relatively inexpensive since they are performed in situ and are solar-driven.

Field trial of transgenic Indian mustard plants shows enhanced phytoremediation of selenium-contaminated sediment.

Three transgenic Indian mustard [Brassica juncea (L.) Czern.] lines were tested under field conditions for their ability to remove selenium (Se) from Se- and boron-contaminated saline sediment.

Speciation of volatile selenium species in plants using gas chromatography/inductively coupled plasma mass spectrometry.

Gas chromatography/inductively coupled plasma mass spectrometry (GC/ICP-MS) coupled with solid phase micro-extraction can provide a simple, extremely selective and sensitive technique for the analysis of volatile sulfur and selenium compounds in the headspace of growing plants. In this work, the technique was used to evaluate the volatilization of selenium in wild-type and genetically-modified Brassica juncea seedlings. By converting toxic inorganic selenium in the soil to less toxic, volatile organic selenium, B.

Overexpression of selenocysteine methyltransferase in Arabidopsis and Indian mustard increases selenium tolerance and accumulation.

A major goal of phytoremediation is to transform fast-growing plants with genes from plant species that hyperaccumulate toxic trace elements. We overexpressed the gene encoding selenocysteine methyltransferase (SMT) from the selenium (Se) hyperaccumulator Astragalus bisulcatus in Arabidopsis and Indian mustard (Brassica juncea). SMT detoxifies selenocysteine by methylating it to methylselenocysteine, a nonprotein amino acid, thereby diminishing the toxic misincorporation of Se into protein.