2-Plants: Transgene containment in chloroplasts "not a magic bulletsolution"
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-------------------------------- GENET-news --------------------------------
TITLE: New fears raised about GM plants
SOURCE: The Age, Australia, by Stephen Cauchi
DATE: Feb 6, 2003
------------------ archive: http://www.gene.ch/genet.html ------------------
New fears raised about GM plants
Further questions have been raised about consequences of growing
genetically modified plants after Australian scientists showed that a
hoped-for method of preventing "superweeds" does not work.
Scientists had hoped that by injecting foreign genes away from a plant
cell's nucleus, the GM plant's pollen would remain free of the genes and
not infect other plants.
This week's edition of the science journal Nature says University of
Adelaide researchers have shown that even if foreign genes are injected
elsewhere in a cell, the genes can "hop over" into the nucleus and end up
in the pollen.
In theory, the pollen is then free to crossbreed with wild flowers and
weeds, creating superweeds resistant to herbicides.
When genetically modifying a plant, scientists usually introduce foreign
genes directly into the nuclei of the plant's cells.
A consequence is that the foreign DNA ends up in pollen.
American and French researchers last year showed that weeds and GM crops
- of sunflowers and sugarbeet - readily cross-bred and swapped genes.
Australia has several trial fields of GM crops, such as canola.
To try to avoid the problem, some GM plants had foreign genes inserted
into the chloroplasts - the part of the cell that turns light into
chemical energy for the cell - instead of the nucleus.
"Whereas DNA in a cell's nucleus is incorporated into pollen as cells
divide, chloroplast DNA stays put," according to Nature. "But not all the
time, as Jeremy Timmis at the University of Adelaide and colleagues now find."
Dr Timmis, associate professor of molecular biosciences, and two
colleagues from the CSIRO's plant industry division, inserted a "marker"
gene into the chloroplasts of tobacco plants and then looked for it in
about 250,000 of the plants' offspring.
In about one in 16,000 seedlings, the gene had jumped from chloroplast to
the nucleus and was being "expressed in a heritable manner," according to
"It's very good that we have found out about this," said Peter Wills, a
theoretical biologist at the University of Auckland. "It's a good way of
"This is an idea that's been talked about for quite a while. They were
certainly hoping that this would be a method of preventing many
Professor Wills said the research showed injecting genes into
chloroplasts instead of the nucleus "was not a magic bullet solution".
"We are bound to cause cock-ups," he said. "It's not very surprising
because of the nature of biological systems."
Professor Wills said the rate of one in 16,000 "sounds like a very large
"Once you know there is traffic from the crop to the wild you know you
are going to have a certain level of contamination through pollen. You
won't get the brick wall in place."
But a senior lecturer at Melbourne University's Botany School, Edward
Newbigin, said that although the rate was not zero, it was "not going to
While the foreign gene infected one seed in 16,000, only one seed in
about 10,000 made it to a neighbouring non-GM field. This was a total
rate of one seed in 160 million, he said.