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PLANTS: U.S. researchers plan to develop GE plants to grow betterunder acid rain



------------------------------- GENET-news -------------------------------
TITLE:  Plants' management of nutrient suggests environmental remedies
SOURCE: Duke University, USA
AUTHOR: Press Release
URL:    http://dukenews.duke.edu/2007/03/plantcalcium.html
DATE:   08.03.2007
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Plants' management of nutrient suggests environmental remedies
Scientists' findings may lead to possible genetic 'trickery' to ensure
calcium stays available to build cell walls

Durham, NC -- A new understanding of how plants manage their internal
calcium levels could potentially lead to genetically engineering plants
to avoid damage from acid rain, which robs soil of much of its calcium.

"Our findings should help scientists understand how plant ecosystems
respond to soil calcium depletion and design appropriate strategies to
protect the environment," said Zhen-Ming Pei, a Duke University
assistant professor of biology who led the study, to be published in the
Friday, March 9, issue of the journal Science.

The research was supported by the National Science Foundation, the U.S.
Department of Agriculture and Xiamen University in China.

Calcium enters plants dissolved within the water that roots take in from
surrounding soil. As the water circulates through a plant, its dissolved
calcium gets shuttled where it is needed to give the plant's cells their
structural rigidity. To grow, a plant needs a reliable supply of
calcium. But calcium supplies coming into the plant cycle up and down
over the course of the day, dropping to a minimum at night.

Plants use molecular sensors and flows of chemical messengers to detect
and regulate the storage and distribution of vital nutrients such as
water and calcium.

To track the calcium sensors in the model mustard plant Arabidopsis, the
team used molecules originally found in jellyfish that emit light in
response to calcium's presence. To deduce what the sensor does and does
not do, the researchers also introduced an "antisense" version of the
calcium-sensor protein that abolishes the sensor's effects.

The calcium-sensing molecule in plants, called CAS, was first identified
by Pei's group and described in the Sept. 11, 2003, issue of the journal
Nature. Arabidopsis is favored for such experiments because it has a
relatively short life cycle of eight weeks and its genome has been
completely sequenced.

By tracking the glow of the jellyfish molecules, the researchers learned
that CAS plays a number of roles in plants. The scientists initially
thought it simply monitored changes in levels of dissolved calcium that
enters the plant from the outside. They discovered instead that CAS also
triggers the release of internal calcium that is stored within the plant
via a chemical signaling system.

This coupled system, the researchers deduce, ensures that constant
levels of calcium remain available to a plant's cells despite widely
varying amounts of the nutrient coming in during each day and night cycle.

"The sensors try to detect how much calcium is there, and they
coordinate that level with growth and development," Pei said. "If they
detect there is not enough calcium, the plant may elect to hold off on
growth and development until it has more calcium. The plant may thus
appear not to be doing well."

The findings have prompted Pei to begin a new research program aimed at
altering this calcium balancing act to help plants adjust to the ravages
of acid rain.

Produced by interactions between water vapor and human-created
pollutants, acid rain can disrupt plants' calcium balance by leaching
significant amounts of calcium from agricultural and forest soils as
well as from plant leaves, according to Pei.

"It has been found that some soils have lost as much as 75 percent of
their calcium during the past century," he said. "One way to respond is
to add new calcium to the soil. But we can't do that everywhere that
it's needed and it is also expensive."

Although acid rain robs soil of much of its calcium, enough is still
left for plants to live on, Pei added. But he suspects that sensors like
CAS may misinterpret "less" as "too little" in those plants and
unnecessarily signal for growth shutdowns. Perhaps a plant's calcium
sensors could instead be tricked into interpreting "less" as "still
enough" and keep building new cell walls, he suggested.

As a preamble to such genetic engineering, Pei is now leading a study in
his native China that will evaluate the physiology of various plants
affected by acid rain. "It is in the south of China where acid rain is
huge because of industry," he said. "China is becoming the factory for
the United States.

"We will monitor calcium changes in the soil there, and then clone
calcium receptors from various plant species to see whether those
receptors are responsible for growth and how they respond to acidity,"
he said. "Some plants grow terribly under acid rain, but others grow
very well."

Other Duke researchers who participated in the current study were
postdoctoral researchers Ru-Hang Tang and Shengcheng Han; Hailei Zheng,
a visiting professor from Xiamen University; Charles Cook, a laboratory
technician; Christopher Choi, an undergraduate student; Todd Woerner, a
chemistry instructor; and Robert Jackson, a professor of biology and
environmental science and director of Duke's Center on Global Change.

For more information, contact: Monte Basgall | (919) 681-8057 |
monte.basgall@duke.edu


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