Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Arsenic hyperaccumulating ferns: How do they survive?

Arsenic is toxic to most forms of life, and occurs naturally in soil and ground water in many regions of the world. Chronic exposure to arsenic has been linked to lung, bladder and kidney cancer, and thus there are strict limits on allowable levels or arsenic in drinking water.

Chemically similar to phosphorus, arsenic forms arsenate (AsO43-), which closely resembles phosphate (PO43-). Arsenate interferes with many phosphate-requiring metabolic reactions, including synthesis of adenosine triphosphate (ATP), a ubiquitous and essential source of cellular energy. Thus, exposure to even low levels of arsenic can be extremely toxic.

In well-aerated soils, arsenic exists mainly as arsenate, which is taken up by plant roots using a phosphate transporter protein. Plant tissues rapidly reduce arsenate to arsenite (AsO33-), which is transported to the aerial portions of the plant. In aquatic environments or water-logged soils, arsenic exists primarily as arsenite. Whereas rice grains can accumulate up to 60 ìg/g arsenic, the fern Pteris vittata (see figure) can hyperaccumulate arsenic to levels 1000-fold greater than this. A team of researchers led by David Salt and Jo Ann Banks of Purdue University have recently isolated a gene encoding an arsenite transporter protein. This transporter allows these ferns to sequester arsenic in the vacuole, a cellular storage compartment isolated from the cytoplasm by the vacuolar membrane.

In research recently published in The Plant Cell and performed primarily by graduate student Emily Indriolo (now a researcher at the University of Toronto), these scientists describe how they used an arsenic-sensitive strain of yeast to isolate and characterize a gene encoding the P. vittata arsenite transporter. Yeast cells are arsenic-resistant because their plasma membrane contains an arsenite effluxer protein that is encoded by the Arsenical Compound Resistance 3 (ACR3) gene. The researchers introduced a library of P. vittata genes into an arsenic-sensitive acr3 mutant yeast strain and isolated a gene that restored arsenic resistance to this mutant. The protein encoded by this gene was then demonstrated to be very similar to the ACR3 protein of yeast in both structure and function.

Sequence analysis showed that this fern protein contains 10 putative transmembrane domains, suggesting a cellular membrane location. Using an antibody that specifically recognizes the ACR3 protein, they showed that ACR3 is found in the membranes of vacuoles, but not in the plasma membrane or in endoplasmic reticulum membranes. This suggests a mechanism for arsenic tolerance in P. vittata tissues: arsenite that enters the cell is transported by ACR3 into the vacuolar compartment, where it is spatially isolated from the cell cytoplasm, the site of many of the cell's arsenic-sensitive metabolic reactions.

Furthermore, the researchers showed that ACR3 gene expression in P. vittata is induced more than 30-fold in the presence of arsenite. To verify that ACR3 is required for arsenic tolerance, the ACR3 gene was silenced using an inhibitory mRNA. In these silenced plants, ACR3 expression was not induced by arsenite, and arsenic significantly reduced the growth rate of these ACR3-deficient plants relative to unsilenced plants.

Sequence analysis showed that, although this gene is found in a wide range of organisms including bacteria, fungi, mosses and gymnosperms, it is absent in angiosperms. By studying the occurrence and function of ACR3 in various plants, including hyperaccumulating and nonaccumulating ferns, the authors hope to provide additional insights into mechanisms of arsenic transport, tolerance, and accumulation. In addition to potential benefits for human health, this research will hopefully lead to strategies for phytoremediation of arsenic-contaminated soil and water.

This work was supported by the National Science Foundation and the National Institutes of Health with technical assistance from the Purdue Ionomics Center.

Gregory Bertoni | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Gene therapy shows promise for treating Niemann-Pick disease type C1
27.10.2016 | NIH/National Human Genome Research Institute

nachricht 'Neighbor maps' reveal the genome's 3-D shape
27.10.2016 | International School of Advanced Studies (SISSA)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

How nanoscience will improve our health and lives in the coming years

27.10.2016 | Materials Sciences

OU-led team discovers rare, newborn tri-star system using ALMA

27.10.2016 | Physics and Astronomy

'Neighbor maps' reveal the genome's 3-D shape

27.10.2016 | Life Sciences

More VideoLinks >>>