GENET archive


2-Plants: GE Arabidopsis attracts predatory mites to fight plant-eating spider mites

------------------------------- GENET-news -------------------------------

TITLE:  Genetically Altered Plant Attracts Bug "Bodyguards"
SOURCE: National Geographic News, USA, by James Owen
DATE:   22 Sep 2005

------------------ archive: ------------------

Genetically Altered Plant Attracts Bug "Bodyguards"

A new genetically modified plant uses chemical signals to invite
predatory bugs to dine on unwelcome guests munching on its leaves.

The enhanced weed--a type of small mustard plant (Arabidopsis thaliana)--
was able to summon bug "bodyguards" after researchers inserted a gene
from a strawberry plant.

A. thaliana is the first plant to have its entire genome sequenced and so
is regularly used in plant research. The genetically modified version of
the weed may lead to a new method of crop pest control that reduces the
need for chemical pesticides.

"This would deliver crop defense in the seed rather than in a spray,"
said John Pickett, head of biological chemistry at Rothamsted Research in
Harpenden, England.

"This is the first time that a plant has been modified genetically to
produce a [predator] attractant," he added. "Exploiting this process is
really very important."

The study team reports that the genetically engineered plant was able to
attract predatory mites (a small relative of spiders) that prey on plant-
eating spider mites. The development is reported in tomorrow's issue of
the journal Science.

Active Ingredient

Study co-author Harro Bouwmeester, a biochemist at Plant Research
International at Wageningen University in the Netherlands, says the plant
needed little genetic modification to introduce the chemical lure.

"It's very commonplace in the wild for plants to emit bodyguard-
attracting compounds upon insect feeding," he said.

"Because this phenomenon is widespread in the plant kingdom, it means the
machinery to produce these compounds is available in all plants. That
means you just have to tap into existing pathways [in plant cells], and
that can be done by the introduction of just one gene."

Bouwmeester says the active ingredient varies somewhat between plant
species, but most bug attractants rely on complex compounds called terpenes.

"You will know terpenes from the smell of certain herbs like peppermint,"
he said. "Other plants also produce these compounds, but in lower
concentrations so we don't smell them."

Many crop plants already produce small amounts of terpenes, including
corn (maize), apples, beans, cucumbers, and cotton.

Bouwmeester adds that bodyguard-attracting compounds work best when
emitted by the plants themselves. Spraying crops with similar man-made
chemicals would be less effective given the delicate balance of
interactions between a plant, pests, and predators.

"You only want to attract these predators at the exact moment [their]
food source, such as the spider mite, is there," he added.

In the wild, plants lure a range of predatory bugs that perform a vital
pest control service. These helpful dinner guests include aphid-chomping
ladybugs and parasitic wasps that lay eggs inside caterpillars.

Pickett of Rothamsted Research says plants are often highly sophisticated
in their signaling. The plants can tailor their messages for specific
predators depending on which pest species is taking a bite out of them.

For instance, he says, "There are three aphid species that attack beans:
the vetch aphid, the black bean aphid, the pea aphid.

"But a particular parasitoid [a parasite that kills its host] can only
develop in the pea aphid. And that parasitoid can tell from the signals
coming out of the bean plant whether it's only the pea aphid that's there."

Crop Yields

Pickett says the Dutch-led team's research may allow humans to harness
plant-bug interactions to improve crop yields.

"Nature's only evolving to create a balanced situation," he said. "But we
need to create food, which inevitably disrupts that balance. As soon as
you grow a monoculture you need pest control, so these new approaches are
going to be very important."

"There's a tremendous demand for alternatives to pesticides, not only
because of people's fear of pesticides, but also because insects develop
resistance to them," Pickett added.

But many advocacy groups have heavily criticized development of
genetically modified crops. The man-made plants pose a serious risk to
the natural environment, they say.

Pickett says this latest plant should be no cause for alarm.

"Nobody needs worry because all the genes are from the plant kingdom--it's
just that [the researchers have] done some genetic tricks," he said.

The research could also help create a new generation of bodyguard-
attracting crops without high-tech genetic modification, according to
study co-author Bouwmeester.

He says a major goal of the team's research is to identify which plant
chemicals act as bug attractants.

Once these compounds are identified, he says, "We think that with normal,
traditional breeding it would as well be possible to improve the ability
of plants to lure predators."


European NGO Network on Genetic Engineering

Hartmut MEYER (Mr)
In den Steinäckern 13
D - 38116 Braunschweig

P: +49-531-5168746
F: +49-531-5168747
M: +49-162-1054755
E: coordination(*)
W: <>

   GENET-news mailing list