Genetic engineers may recast tobacco

August 08, 1994|By Knight-Ridder News Service

To Elizabethan Robert Burton, tobacco was "a plague, a mischief . . . devilish and damned." Oliver Wendell Holmes, the 19th-century jurist, condemned it as "the filthy weed."

Today, just as the latest campaign against tobacco reaches a fever pitch, genetic engineers are exploring techniques that could redeem the plant's reputation, transforming it from the herbal equivalent of Public Enemy No. 1 into a candidate for Man's Best Friend.

Biotechnology researchers say tobacco plants are the ideal biological factory for manufacturing everything from new drugs and vaccines to food ingredients and industrial compounds.

Several companies already are planning products based on the technique. And some tobacco farmers, worried about the future of what has been a very lucrative crop, are getting interested.

"I get a lot of calls from agricultural extension specialists and producers inquiring about the possibility of growing tobacco for other uses," says Glenn Collins, a geneticist with the University of Kentucky. "It's very much being discussed."

Tobacco has long been a favorite of gene research labs. It is easy to grow and breed, with a biochemistry that's well understood and easily manipulated. The plants are willing hosts for foreign genetic material, accepting even human genes and reproducing them as their own.

Now, researchers are ready to move beyond the testing phase, planting fields with acres and acres of altered tobacco plants, all busily churning out valuable chemical compounds.

"I think the biotech industry is poised for the second revolution," says Ray Rodriguez, a professor of genetics at the University of California, Davis. "And that is high-volume, low-cost manufacturing. And there's only one way to do that: with agricultural systems."

The practice, known as "pharming," has already yielded astonishing results in experimental fields and barnyards. Scientists have bred potatoes containing a human blood protein, rapeseeds laced with a pain-killing brain chemical, goats that produce heart-attack drugs and sheep whose tissues carry a treatment for emphysema.

But for commercial ventures, many say it's tobacco that holds the most promise. Large and abundant leaves offer a huge mass of organic material, much of which the plant can turn over to biochemical production. It also can manufacture several substances at once, allowing companies to extract multiple products from the same plant.

What's more, although tobacco is a simple organism, it can synthesize complex molecules scientists once thought only mammals could make. And using plants as living factories avoids the ethical concerns associated with animal systems.

Biosource Genetics Corp. of Vacaville, Calif., has developed a technique for inserting genes into individual tobacco crops that it says should help make such a plan economical. Rather than modifying the plant itself, Biosource scientists splice new genes into a common tobacco virus and distribute it over the leaves.

The virus takes over the plant's cells, re-coding them to manufacture the desired biochemicals. They are then extracted when the harvested plants are processed.

The company compares its technology, dubbed "geneware," to the process of loading a program disk into a personal computer. The virus carries the new genetic instructions to the tobacco cells, which executes them like a program. The plant's own DNA is not affected. And while the program can't be turned off, it disappears with the infected tobacco generation.

By altering crops instead of genes, Biosource avoids a costly investment in engineered plant strains. And the company could program tobacco fields to produce different products every year.

"We can make virtually anything for which we have genes," says Biosource President Robert L. Erwin.

Among the most promising is a biodegradable plastic that could replace the petroleum-based polyethylenes now used in food containers and disposable diapers. The plastic is made from a polymer normally created in bacteria.

By transferring the polymer to tobacco by way of its genetically engineered virus, the company hopes to make the plastic inexpensive enough to compete with conventional products. It has developed a genetic prototype and hopes to start field production sometime next year.

"We're quite optimistic about it," Mr. Erwin says.

Several months ago, Biosource also signed a contract with the University of California, Irvine to develop a new class of tobacco-grown antibiotics. Michael Selsted, professor of pathology in the university's College of Medicine, says the plant offers the most economical way to make the kind of powerful antibiotics able to attack drug-resistant bacteria strains, such as tuberculosis.

"You can grow fields and fields of it," Mr. Selsted says. "It turns out to be very competitive with virtually any other process people can use."

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