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Switch on crop protection

New seed research aims to turn traits - such as cold tolerance or pollination timing - on and off when needed.

We are all accustomed to flipping a switch to turn on a light or to start a computer. But in the near future, we also may be able to "switch on" certain traits in plants, such as cold tolerance or higher starch content. If current research comes to fruition, the crops you plant could very well come equipped with "switches" that activate the expression of certain genes to protect the crop or enhance its value.

At Michigan State University (MSU), researchers have found a transcription factor that regulates the expression of cold-regulated genes. Transcription factors bind to the regulatory sequences of genes and can act as master switches to turn on gene expression. Under the direction of Michael Thomashow, molecular genetics professor, MSU researchers used a transcription factor called CBF1 to turn on cold tolerance in Arabidopsis, a member of the mustard family.

Taking the bite out of cold snaps. This research could have implications for corn and soybean growers who periodically contend with cold snaps in the spring or fall. It also could have implications for fruit and citrus growers, who suffered significant crop damages from freezing in 1998.

Cold-regulated genes are normally expressed gradually as plants are exposed to slowly falling temperatures. As a result, plants are more susceptible to damage under sudden temperature drops.

In the MSU tests, overexpression of the CBF1 transcription factor turned on the Arabidopsis plant's cold-regulated genes throughout the plant's life. Moreover, the cold-tolerance performance of transgenic Arabidopsis plants was similar to that of plants that are conventionally acclimated to the cold.

Because other crops may not have the same number or type of cold-regulated genes as Arabidopsis, further studies are necessary. However, the positive impact that cold-tolerance control could have on crop production should spur continued research. "By manipulating the cold-sensing system, we could help prevent losses and expand ranges where crops would be safe," says MSU's Thomashow. He adds that if researchers were able to enhance the cold tolerance of plants, farmers could plant crops that tend to yield more (such as winter canola vs. spring canola). The safe growing season of spring crops could be lengthened, which would result in an increase in yield.

MSU has filed patents for the cold-tolerance gene technology and has formed a licensing agreement with Mendel Biotechnology, an agricultural genetics research company based in Hayward, CA. Mendel Biotechnology is commercializing the technology.

Michael Fromm, Mendel's president and CEO, says his company is looking for partners to move the CBF1 technology through the marketplace. The discovery has already attracted some early technology adopters from the forestry, agronomic and vegetable crop industries.

From the lab to the field. CBF1 research is still in its infancy. However, Fromm expects that more companies will license the technology as testing progresses. The possibility that CBF1 could also play a role in drought tolerance should increase the level of interest, says Fromm. He points out that Texas alone suffered ยค1.6 billion in agricultural losses from last year's drought. And, in 1995, between 5 and 10% of the nation's corn and soybean crops was damaged by an early fall frost. CBF1 technology could help growers significantly reduce millions of dollars worth of frost and drought damages, Fromm suggests.

He adds that the technology could enable California growers, for example, to produce certain vegetable crops that need just a little more freezing tolerance during winter months.

In the field, farmers could turn on the CBF1 transcription factor by applying an environmentally safe spray before a cold snap, says Thomashow. Such a chemical spray could be used to "manage" expression of the plant's natural freezing tolerance mechanisms.

How soon could crops incorporating CBF1 technology be on the market? Again, testing is still in its early stages. Fromm estimates that it would take at least three to five years before such technology would be found in commercial products.

Insect and disease resistance. Scientists also are looking at how to control insect- and disease-resistance gene expression in plants. "Switch technology, particularly in terms of resistance management, is exciting," says Jon Scharingson, field crops manager, Zeneca Ag Products. He provides an example: A chemical (possibly even a simple molecule) could be used to activate a regulator gene in cotton that conveys disease resistance for a critical period of time when a particular disease is most likely to infect the plants. The gene may only need to "kick in" for ten days, for example.

Scharingson notes that Zeneca has conducted "proof of concept" tests on gene switch technology in the areas of disease and insect resistance. These tests have involved cotton and canola. The company plans on developing the technology in corn and soybeans, as well as cotton, tomatoes, potatoes, bananas, wheat and rice.

Monsanto also is in the early stages of switch technology research.

In general, switch technology will likely be developed to express "input" genes first. This is because single-trait genes are easier to manipulate than multiple-trait genes generally associated with altering the food or feed quality of crops.

A boost in value. The ability to control the expression of either input or output traits, however, should provide growers more flexibility. It's possible that during the production season, a grower could modify No. 2 yellow corn into a crop with higher starch content for a wet miller, for example. Growers could take advantage of market shifts or premiums if they could modify grains or oilseeds closer to harvest.

Or a grower might use switch technology to tell the corn plants when to tassel and shed pollen. This would have significant implications; pollination time of a crop is extremely important to its ultimate yield.

Erica Pascale, staff scientist, Novartis Agribusiness Biotechnol-ogy Research, notes that switch technology has the potential to modify traits as a crop gets closer to harvest (such as increasing the levels of lysine and other amino acids), without hindering plant growth.The application of the technology will depend on the particular crop and product.

Pascale claims that switch technology is applicable to a wide array of species. She says, "It will be particularly helpful in specialty products that bring high value."

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