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2-Plants: GM potato uses frog gene to resist pathogens

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TITLE:  GM potato uses frog gene to resist pathogens
SOURCE: SciDev.Net, UK, by Wagdy Sawahel
DATE:   28 July 2005

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GM potato uses frog gene to resist pathogens

A chemical that South American frogs excrete from their skin could
protect potatoes and other crops from a range of diseases, according to
biotechnologists in Canada.

Researchers at the University of Victoria inserted a modified frog gene
into potato plants to make them produce the chemical.

The genetically modified (GM) potatoes showed resistance to infection by
a broad range of disease-causing fungi and bacteria, including those
responsible for diseases such as dry rot, late blight and pink rot.

Different species of frog produce different sets of chemicals, including
some called dermaseptins, from their skin depending on the environment
they inhabit. The chemicals help protect frogs from bacteria and other

The most potent dermaseptin, known as B1, has been isolated from the skin
of tree frogs called Phyllomedusa bicolor that live in the rainforests of
South America, where the hot and humid conditions mean fungi and bacteria

The Canadian team showed that a synthetic version of dermaseptin B1
inhibited the growth of "an exceptionally broad range" of fungi that
cause plant diseases, as well as the bacterium Erwinia carotovora, which
causes blackleg in potato plants in the field and soft rot of tubers in

The researchers genetically modified potatoes to produce the chemical and
exposed the GM plants to the same organisms. The inserted gene gave
"unusually broad-spectrum and powerful resistance to infection",
according to the team's research, which the journal Theoretical and
Applied Genetics published online in June.

Santosh Misra, who led the work, told SciDev.Net the approach could help
farmers in developing countries to reduce pesticide use, increase yields
and reduce losses of crops stored after harvest.

Fungal and bacterial infections can cause heavy losses of potato crops.
The standard approach has, in recent decades, been to spray crops with
pesticides, but this can be damaging to the environment and farmers'
health, and encourages the fungi and bacteria to develop pesticide-resistance.

Misra's team says that because their GM potatoes could resist so many
types of disease-causing organism, the same gene could be used to protect
other crops such as wheat, barley and sugar.

The researchers say that the preliminary results of studies to show the
safety of dermaseptin B1 "are positive". They add that the GM plants
showed no ill effects of having been genetically modified.

Eric Messens, professor of plant molecular genetics at Flanders
Interuniversity Institute for Biotechnology at Ghent University, Belgium,
says the research into the safety of GM crop using genes that produce
toxins should precede the main research, not follow it.

Messons told SciDev.Net that it was important to test if dermaseptin B1
is toxic to people and animals, as well as study whether the chemical
gets broken down or builds up in the body.

"Long-term effects must be taken into consideration because even though
the authors claim that the amount of dermaseptin is low, the accumulation
effect can not be ignored," said Messons.

For example, said Messons, long-term consumption of peas called Lathyrus
sativus can cause paralysis if a toxin in the peas accumulates in people,
as has happened in Bangladesh and India.

Messons suggests that safety could be improved by ensuring that GM
potatoes only produce dermaseptin B1 when they become infected, and then
only in the skin of the potato, which could then be removed by peeling.

Link to abstract of paper in Theoretical and Applied Genetics
Reference: Theoretical and Applied Genetics doi: 10.1007/s00122-005-2056-y


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