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Finding A Way To Thrive

Posted Jul. 9, 2009

Genetic transformation aids researchers' quest to build drought-tolerant grasses and legumes.
Genetic transformation may help grasses and legumes, such as this alfalfa plant, survive diseases and tolerate harsher environmental conditions, specifically drought.
Genetic transformation may help grasses and legumes, such as this alfalfa plant, survive diseases and tolerate harsher environmental conditions, specifically drought.
Zeng-Yu Wang
Zeng-Yu Wang examines an alfalfa leaf. Wang is looking to improve grasses and legumes through genetic transformation.

To most of us, grass is grass. We mow it in the summer or shoot a golf ball across it now and then, rarely giving a thought to the fact that more than one-quarter of the Earth's land is carpeted in hues of green. Some grasses thrive in cool weather, some across sunburned plains, some at altitudes few humans ever experience. Without grass, animals wouldn't survive, and neither would people who depend on them.

To scientists, grass is never just grass. Countless species of plants comprise what the rest of us refer to as grass, some of which - like clover - aren't really grass at all, but pod-bearing legumes. To researchers who study them, grasses and legumes are a diverse and dynamic cornerstone of life and agriculture. "Grasses and legumes can grow where crops cannot," said Zeng-Yu Wang, associate professor, who heads up genetic transformation research in the Noble Research Institute's Forage Improvement Division.

Yet for all of their versatility, the world's most important plants still exist at the mercy of nature. A prolonged drought has withered pastures throughout much of the country, forcing many farmers and ranchers to feed livestock that ought to be grazing. Wang envisions a day when grasses keep growing in parched soils, with varieties of legumes such as alfalfa and white clover better equipped to draw nutrients and resist months of little rain. These plants don't exist now. That's why he is trying to make them.

His laboratory is Noble's epicenter for research into genetic transformation. In its simplest sense, genetic transformation is the science of altering a plant's genetic makeup. Humans have tinkered with the genetics of plants for centuries, which is one reason the impossibly plump, perfectly colored fruits and vegetables in the supermarket bear little resemblance to anything your ancestors ate. Traditionally, plant breeders turn up the volume on desirable qualities or winnow out less beneficial traits through selective crossing of certain plants. Wang's work tries to fast-forward the process. Instead of breeding whole plants, or even shoots of plants, Wang's laboratory inserts genetic instructions directly - in this case, codes that might enable a plant to absorb more phosphate from the soil or withstand long periods without rain.

The work is painstaking, complex and controversial. Yet for a man born and educated in China, challenge is something to embrace. "I thoroughly enjoy the work because of its tremendous potential benefits to food security and the environment," he said.

As a scientist, Wang knows to expect results in increments, not eureka moments. Each step of the work takes him from molecular genetics to plant breeding to tending seemingly endless generations of plants. He and his colleagues begin with the genetic instructions for the naturally occurring waxy layer on the outside of an alfalfa plant. Experiments suggest that thickening this almost invisible coating enables alfalfa to lose less internal moisture through evaporation and reduce its thirst for water in the same way car wax protects a paint job from the scorching sun. In a sense, the goal is to give the plant an ability to detail itself.

Which is where Agrobacterium comes in. Agrobacterium is a microorganism that uses plants for its own survival. When Agrobacterium needs food, the organism seeks to infect a host plant. Once infected, Agrobacterium has the ability to place its own genes among the plant's genes. In genetic transformation research, scientists use Agrobacterium's unique gene transfer talent for their own ends. Researchers insert genes of interest into the Agrobacterium "vehicle" - genes that they want the plant to use. They then allow Agrobacterium's natural mechanism to work.

"What we do is start putting our own genes in," Wang said. When it infects a plant, Agrobacterium will transfer whatever genetic cargo it contains - be it the organism's own genes or stowaways inserted by scientists.

But placing a gene into the plant's seed is, in many ways, the easy part. Insertion of the gene inside the plant's genetic machinery doesn't guarantee the gene will be expressed - meaning that it might sit silently buried in the seed. Or it might produce the changes in the wrong place. "You want this gene to be expressed in certain cells at certain times in the plant," Wang said. And there lies the biggest challenge.

In Wang's work, he wants the increase in wax to appear on the outside edge of the plant, not throughout. If the thickening occurs elsewhere, the plant might grow too slowly or have a poorer nutritional value. Also, he said, "you only want the gene expressed in times of drought."

The same challenges appear in another line of experiments, this time with coaxing plants to absorb more phosphate. Phosphate is an essential nutrient for plants, but the majority of the mineral remains trapped in the dirt because the plant doesn't have a good mechanism to absorb it. Wang is experimenting with two genes that code for enzymes that allow phosphorus to more easily pass into the plant. He faces the same challenge of precision: he only wants the genes expressed in the plant's roots.

The targets of these experiments are alfalfa and white clover, both of which are important forage legumes for livestock. The work is partly funded by Forage Genetics International, a subsidiary of the Land O'Lakes corporation, known for producing other genetically engineered products.

In addition to the scientific realities, Wang also knows that genetic transformation is a rough terrain for public policy. One of his mentors was Ingo Potrykus, a professor at the Swiss Federal Institute of Technology in Zurich, who helped develop golden rice. Golden rice, which contains a gene that makes vitamin A, could help protect much of the developing world from blindness. At its introduction in 2000, the rice was hailed on the cover of Time magazine. Yet it has not yet been adopted in some of the world's highest rice-consuming, vitamin A-deficient countries because the idea of directly altering the genes of plants makes many consumers wary.

"There will be people against it, no matter what you do," Wang said. In the United States, genetically modified plants are widespread: 80 percent of corn, 86 percent of cotton and 92 percent of soybeans are genetically engineered.

"I think it's a critical technology that's going to be around for a while," said Ed Kaleikau, National Program Leader in plant genetics at the United States Department of Agriculture's Cooperative State Research Education and Extension Service. "It will be useful in increasing the production of crops, particularly as the population is growing."

Wang hopes what is true for food crops will one day apply to forage plants. People depend on grass and legumes, he points out, even if they never think about the stuff under their feet.

And if the research goes well, they won't have to.

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