Farmers one day may be able to flip the molecular switch that makes plants tolerate freezing temperatures, thanks to new insight Michigan State University scientists have gained about plants’ mechanisms to cope with cold.

According to a report published in the April 3 edition of Science Magazine, molecular geneticist Michael Thomashow and his associates report that increasing a plant’s expression of a specific regulatory gene helps throw the plant into cold-coping mode, beefing up its defenses against freezing.

"If we have the molecular switch to turn off and on the genes at will, we can potentially lengthen the safe growing season," Thomashow said. "This is significant information that has the potential of modifying the natural process and tailoring it to specific needs."

Plants always have had what it takes to adjust to drops in temperatures – but they need warning. A cherry tree faced with a cooling trend can shift into protective behavior, bracing itself to weather gradual freezes.

But sudden freezes – such as those seen across the nation in recent weeks – can sound the death knell because they catch a plant unawares.

Traditional plant breeding over the past century has made little progress in increasing cold tolerance.

Thomashow, a professor of crop and soil science, along with research associates Eric Stockinger and Sarah Gilmour and graduate students Kirsten Jaglo-Ottosen and Daniel Zarka, dove into the molecular lives of plant cells to understand how a plant turns on its cold tolerance mechanisms in the plant’s DNA sequence.

Their work has led to the identification of a regulatory gene – called CBFI - that encodes a protein which ultimately turns on the COR, or cold-regulated genes.

Over expression of CBF1 induces COR gene expression without the presence of cold temperatures. In effect, it fools the plant into thinking a cold spell has struck.

The COR genes act, at least in part, by stabilizing membranes – the primary site of freeze-induced injury.

Identifying the CBF1 switch holds the promise of giving farmers the ability to turn on that switch when needed.

Thomashow and the others did their initial work on the plant Arabidopsis, a member of the mustard family. But he said that it appears the basic mechanism is highly conserved in plants that have the ability to acclimate to the cold. Tropical plants, such as bananas, may not have the mechanism to begin with and thus might not have the potential to grow in the north.

But there is potential to raise a wide variety of crops in places they currently cannot grow. It could mean protecting a grove of cherry trees from a sudden frost, for instance, or harvesting fields of grain in fields now deemed too cold.

Thomashow can see possibilities in learning to link the cold-regulation gene switch to an environmentally safe spray that farmers could apply before a cold snap to ready the crops.

And since the defense plants employ to ward off cold damage is similar to their defenses against drought, the potential also exists to protect crops from dry weather as well.

Michigan State University, which has filed patent applications on Thomashow’s discovery, has entered into an option to license with Mendel Technologies Inc. of California for the cold and drought resistance technology.

"These are genes that already are in the plant," he said. "We’re talking about turning them on a little sooner or later by modifying the mechanism plants normally use to sense cold temperatures. It’s working with the natural system to optimize it."

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