2-Plants: GE castor beans without toxins and allergenes?

[GENET <genetnl@xs4all.be>]

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TITLE:  High-tech castor plants may open door to domestic production
SOURCE: US Department of Agriculture, Agricultural Research Magazine
        http://www.ars.usda.gov/is/AR/archive/jan01/plant0101.htm
DATE:   January 2001

------------------ archive: http://www.gene.ch/genet.html ------------------


Dear GENET-news readers,

this announcement of another "new generation" GE crop lacks one important 
background information: how to deal with the well knnown unreliability and 
instability of the anti-sense approach? What happens if the suppression of 
toxins and allergens fails due to specific reactions of the plant 
metabolism or due to agro-ecological influences? Who will be liable?

Yours,

Hartmut Meyer

                              *****


High-tech castor plants may open door to domestic production

Inside the beans of the castor plant is a toxin seven times more deadly 
than cobra venom. Known as ricin, the compound's toxicity is one reason why 
American farmers no longer grow this crop extensively - even though a 
lucrative market exists for the castor bean's unique oil. Components of the 
oil, known as hydroxy fatty acids, are essential for making high-quality 
lubricants for heavy equipment or jet engines, for example. Castor oil is 
also used in paints, coatings, plastics, antifungal compounds, shampoo, and 
cosmetics.


Allergens Pose Health Hazard

Besides the ricin toxin, there's another compelling reason why this crop 
has fallen out of favor with U.S. growers. The shiny, beetle-shaped seeds 
contain powerful allergens. People who work with the off-white meal ground 
from castor beans may develop allergic reactions, such as hives or asthma. 
In severe cases, they may go into anaphylactic shock, which can be fatal.

Conventional breeding to rid castor of lethal ricin and troublesome 
allergens hasn't solved the problem. But biotechnology might, according to 
Thomas A. McKeon of ARS' Western Regional Research Center in Albany, 
California. He and colleague Grace Q. Chen, both in the Crop Improvement 
and Utilization Research Unit, are the first in the world to genetically 
engineer castor plants. In preliminary experiments, McKeon and Chen used 
marker genes to determine whether their tactics for shuttling new genes 
into plants actually worked. Now the scientists want to give the plants 
other genes - ones that could, among other things, block production of 
ricin poison and the powerful allergens.


Biotech Strategies

Scientists elsewhere have already isolated and copied a gene critical to 
ricin production, as well as a gene that produces the key allergen proteins 
in castor. McKeon and Chen aim to build and insert slightly different 
versions of those genes into the castor plant, to block the action of the 
ricin and allergen genes. For example, they want to construct antisense 
genes, which are genes that make nonsense copies of the authentic ricin or 
allergen genes. "Antisense genes," McKeon says, "can interfere with the 
gene expression needed for producing ricin and allergens. That may leave 
the plant unable to form these compounds."

Castor plants that are free of ricin and allergens could renew interest in 
farming this crop. That could happen not only in the southern United 
States, where it was grown until the early 1970s, but also in the arid 
Southwest, where it could grow well if irrigated.

"Castor is a semitropical plant that thrives in sunny climates," McKeon 
says. Although some types of castor grow to be 30- to 40-foot-tall trees in 
the Tropics, in the United States castor can be harvested annually when it 
is only about 4 to 5 feet high. In the past, U.S. production has reached 
1,000 pounds of oil per acre. "That's an impressive feat for any oilseed 
crop," notes McKeon.

Production of a U.S. castor crop could ensure a more reliable supply of the 
oil for American industries and for defense. This country depends on 
imports of castor oil, primarily from India. In 1999, America imported 
nearly 103 million pounds of castor oil, worth about $41 million. The world 
demand for castor oil is about 1 billion pounds annually, valued at more 
than $400 million.

Although some other plants, like lesquerella, can produce oil that contains 
hydroxy fatty acids similar to the ones in castor, these alternative crops 
are not yet widely grown commercially. Another approach? Synthesize hydroxy 
fatty acids in chemical factories. Although the technology exists to do 
that, growing castor plants outdoors in the sunshine is a more economical 
approach, McKeon says.


Epoxy Oil - A Possibility?

In addition to reviving production of castor, genetic engineering might 
someday be used to tweak its oil-producing mechanism so that it could yield 
another valued oil, known as epoxy.

Says McKeon, "There is a potential U.S. market of about $300 million a year 
for epoxy oil. An epoxy-based paint, for example, offers all the advantages 
of a premium, oil-based paint, yet does not give off certain volatile 
chemicals that pollute the atmosphere." That's unlike the solvents in oil-
based paints, which can be an environmental hazard.

"We think that production of epoxy oil by castor plants is possible," says 
McKeon, "because the chemical structure of epoxy oil is very similar to 
that of castor oil. The modification that's needed to cue the castor plant 
to make epoxy oil instead of castor oil is minor. That's very different 
than trying to genetically engineer a corn plant or a soybean plant to make 
epoxy oil. The oils that those plants make are very unlike epoxy oil."

McKeon and Chen have produced about a dozen genetically engineered castor 
seedlings in their laboratory and greenhouse. They are applying for a 
patent for their discoveries (U.S. Patent Application No. 60/167,360, 
"Transformation of Ricinus communis, The Castor Plant").

     *****

By Marcia Wood, Agricultural Research Service Information Staff.

This research is part of New Uses, Quality, and Marketability of Plant and 
Animal Products, an ARS National Program (#306) described on the World Wide 
Web at http://www.nps.ars.usda.gov.

Thomas A. McKeon and Grace Q. Chen are in the USDA-ARS Crop Improvement and 
Utilization Research Unit, Western Regional Research Center, 800 Buchanan 
St., Albany, CA 94710; phone (510) 559-5754, fax (510) 559-5768.

"High-Tech Castor Plants May Open Door to Domestic Production" was 
published in the January 2001 issue of Agricultural Research magazine.



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