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June 10, 2008
Source:
BioMed Central, The Open
Access Publisher via
EurekAlert!
Amid recent reports of dangerous
levels of arsenic being found in some baby rice products,
scientists have found a protein in plants that could help to
reduce the toxic content of crops grown in environments with
high levels of this poisonous metal. Publishing in the open
access journal BMC Biology, a team of Scandinavian researchers
has revealed a set of plant proteins that channel arsenic in and
out of cells.
Arsenic is acutely toxic and a highly potent carcinogen, but is
widespread in the earth's crust and easily taken up and
accumulated in crops. Contaminated water is the main source of
arsenic poisoning, followed by ingestion of arsenic-rich food,
especially rice that has been irrigated with
arsenic-contaminated water. According to the WHO, arsenic has
been found approaching or above guideline limits in drinking
water in Argentina, Australia, Bangladesh, Chile, China,
Hungary, India, Mexico, Peru, Thailand, and the US.
Until now, scientists have been unable to identify which
proteins are responsible for letting arsenite, the form of
arsenic that damages cellular proteins, into plant cells. Now
Gerd Bienert and his colleagues from the University of
Copehangen, Denmark and the University of Gothenburg, Sweden,
are the first to show that a family of transporters, called
nodulin26-like intrinsic protein (NIPs), can move arsenite
across a plant cell membrane. NIPs are related to
aquaglyceroporins found in microbes and mammalian cells and
which have already been shown to function as arsenite channels
in these other organisms. Bienert's team put the plant genes
coding for different NIP transporters into yeast cells in order
to test the cells for arsenic sensitivity. The researchers found
that the growth of yeast containing certain plant NIPs was
suppressed when arsenite, one of the predominant forms of
arsenic found in soil, was added to the mix. They showed that
the arsenite was channelled by NIPs and accumulated inside the
yeast cells. Further investigations showed that only a subgroup
of NIPs had arsenite transport capabilities, and have now been
identified as metalloid channels in plants.
More surprisingly, the researchers also found that when they
added arsenate some yeast, cells actually grew better and
arsenite was released out of the cells. "It appears that some
NIPs don't just transport arsenite in one direction", says
Bienert. "They are bidirectional and, given the right
conditions, can clear cells of toxic arsenite as well as
accumulate it. This striking exit of the accumulated arsenite in
cells could have an important role to play in the detoxification
of plants, especially coupled with possibility of engineering a
transporter that discriminates against arsenite uptake in the
first place."
BACKGROUND
1. A subgroup of plant aquaporins facilitate the bi-directional
diffusion of As(OH)3 and Sb(OH)3 across membranes Gerd P
Bienert, Michael Thorsen, Manuela D Schuessler, Henrik R
Nilsson, Annemarie Wagner, Markus J Tamas and Thomas P Jahn BMC
Biology (in press)
Article available at the journal website:
http://www.biomedcentral.com/bmcbiol/
2. BMC Biology - the flagship biology journal of the BMC series
¨C publishes open access research and methodology articles of
special importance and broad interest in any area of biology and
biomedical sciences. BMC Biology (ISSN 1741-7007) is covered by
PubMed, MEDLINE, BIOSIS, CAS, Scopus, EMBASE, Zoological Record,
Thomson Scientific (ISI) and Google Scholar. The journal will
receive its first Impact Factor in 2008.
BioMed Central is
an independent online publishing house committed to providing
immediate access without charge to the peer-reviewed biological
and medical research it publishes. This commitment is based on
the view that open access to research is essential to the rapid
and efficient communication of science. |
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