Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Key Step for Designer Plants that could clean up Heavy Metals

11.08.2003


Researchers at the University of California, San Diego have demonstrated that a chemical that permits plants to detoxify heavy metals can be transported from the roots to stems and leaves, a finding that brings the possibility of using plants to clean up soil contaminated with toxic metals such as lead, arsenic and cadmium one step closer to reality.


Images of plants without (left) and with (right) the gene to produce phytochelatins in roots exposed to cadmium.
Photo Credit Ji-Ming Gong, UCSD.



A paper detailing the discovery appears this week in an advance online publication of the Proceedings of the National Academy of Sciences and will appear in the journal’s August 19th issue.

Bioremediation, the process of using organisms to restore toxic or damaged areas, could substantially reduce the costs of cleaning up the nation’s Superfund sites, estimated to require more than $700-billion. Of the top six pollutants at U.S. Superfund sites, four are heavy metals-lead, arsenic, mercury and cadmium-that may be able to be extracted with the help of plants.


“There are about four important steps in developing plants for bioremediation,” says Julian Schroeder, a professor of biology at UCSD who headed the study. “The roots of the plant need to secrete a substance that makes the metals in the soil soluble, making it possible for the plant to take them up. The plant needs to detoxify the metals once it takes them up, and the metals need to be transported to the stems and leaves of the plant, and stored there. We have found that phytochelatins, chemicals produced by an enzyme for which our lab co-discovered the gene four years ago, unexpectedly function in the root to leaf transfer of metals.”

Prior to his team’s recent discovery, plant biologists presumed that phytochelatins only acted within individual plant cells, surrounding and binding to, or “chelating” heavy metal ions, forming a complex, which is then sequestered in vacuoles—large storage compartments within plant cells. Phytochelatins, in other words, were not known to travel significant distances within a plant.

If the phytochelatins remain in the roots and concentrate the heavy metals there, using plants for bioremediation is much less feasible. That’s because pulling the plants out of the ground with the roots attached is much more difficult than harvesting the parts above ground, and because the leaves and stems produce a lot of new biomass for metal accumulation.

For bioremediation to be practical, heavy metals would need to be transported from roots to shoots. Initially, the UCSD biologists thought it unlikely that phytochelatins could perform this function. “We thought maybe the phytochelatins would be trapped in roots,” says Ji-Ming Gong, a postdoctoral fellow in Schroeder’s lab and the first author on the paper.

To find out, Schroeder’s group used mutant plants that do not make their own phytochelatins. Although phytochelatins are found in most plants, they used Arabidopsis, a relative of the mustard plant, commonly used by plant biologists because of its well characterized genetics and readily available mutant varieties. The researchers took a mutant variety of Arabidopsis, which lacks the genes to synthesize phytochelatins, and genetically modified the mutant plants, targeting the gene for the enzyme that synthesizes phytochelatins to the roots of the plant.

To their surprise, the phytochelatins, while only synthesized in the roots, were found in the leaves and stems as well. In addition, when the researchers exposed the roots of the genetically modified plants to cadmium, arsenate and mercury, the plants had restored resistance to these heavy metals. Furthermore, expression of the gene only in roots increased the accumulation of cadmium in leaves. This suggests that engineering plants with the gene to synthesize phytochelatins in roots could make plants contribute to bioremediation.

“We demonstrated that phytochelatins can be transported from roots to shoots and that phytochelatins have a key role in preventing cadmium over-accumulation in roots and enhancing long-distance cadmium transport to leaves,” says Schroeder.

Cleaning up a site contaminated with heavy metals usually requires extensive bulldozing to remove the affected soil. This is very costly, damaging to the environment and requires a disposal site for the contaminated soil. Plants that can take up and store heavy metals could be a practical and relatively cost effective way of cleaning up contaminated sites. Plants could be grown, harvested and then incinerated to concentrate the heavy metals. Depending on the level of contamination, it might take multiple seasons of growing, harvesting and incinerating the plants to get the concentration of heavy metals in the soil to a safe range.

At present, the researchers concede that they do not understand the mechanism by which phytochelatins are transported from the roots to the shoots. But by better understanding how this occurs, it might be possible to optimize accumulation of heavy metals.

However, as a cautionary note, Schroeder points out, “Over-expressing this gene probably wouldn’t be enough to make plants useful for bioremediation. You would likely need to manipulate other genes in the heavy metal detoxification gene pathway.”

David Lee, a postdoctoral fellow in Schroeder’s lab also contributed to the discovery, which was supported by the National Institute on Environmental Health Sciences Superfund and National Science Foundation.

Contact: Sherry Seethaler, sseethaler@ucsd.edu

Sherry Seethaler | EurekAlert!
Further information:
http://ucsdnews.ucsd.edu

More articles from Life Sciences:

nachricht What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society

nachricht Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>