By Leslie Wimmer
From potential treatments for Alzheimer’s disease to improved forage crops and renewable fuel sources, University of North Texas Distinguished Research Professor Richard Dixon sees plants as opportunities to change the world.
Dixon, who founded the plant biology division at the Samuel Roberts Noble Foundation, is a world-renowned specialist in metabolic engineering of plants. He joined UNT last year as a member of the Signaling Mechanisms in Plants researchcluster, a group confronting the challenge of feeding and fueling a growing population in the face of an increasing need for sustainable, bio-based materials.
A member of the U.S. National Academy of Sciences and a fellow of the American Association for the Advancement of Science, Dixon serves on the editorial boards of five international journals and has been named one of the top 10 most cited authors in plant and animal sciences. He focuses on using metabolic engineering to produce chemicals or alter plants in ways that can improve the health of humans, animals and the planet.
“By altering genes in plants, we are able to experiment with ideas and find potential solutions scientists haven’t thought of before,” he says.
Dixon and his research group recently made a plant science discovery that will lead to the development of new bioproducts from lignin, a substance that makes plants woody and firm. They discovered that lignin can be genetically modified in ways previously thought impossible, and they found plants that produce two types of novel lignin naturally.
“These new lignin polymers provide unexpected opportunities to make biorenewable materials,” Dixon says. “Lignin has been viewed in the past as a waste product of bioprocessing. Adding value to lignin in the biorefinery could provide a much needed economic boost to the lignocellulosic biofuels industry.”
Dixon first began investigating how alfalfa produces lignin in the late 1980s when he joined the Noble Foundation. In the early ’90s, he began identifying the genes in alfalfa involved in making lignin, and over the next few years developed a process of controlling those genes, or slowing down lignin production.
That is important because although alfalfa is the world’s top forage crop, its digestibility is still less than optimal.
“A more digestible variety could lead to better animal performance,” Dixon says, “and to greater flexibility in the harvesting time, as lignin reduces the quality of the forage and conventional alfalfa hay must be harvested prior to extensive lignification.”
Throughout the early 2000s, Dixon began working with Forage Genetics International, the world leader in genetically improved alfalfa. Forage Genetics was interested in Dixon’s low-lignin alfalfa for its commercialization potential.
As the collaboration progressed, the company also began supporting Dixon’s research group in a project to genetically introduce condensed tannins into alfalfa foliage. These compounds slow the rate of protein digestion in the rumen — the cow’s first stomach — resulting in less danger of cattle bloating and improved nitrogen nutrition, which also equates to more milk or meat production.
“Traditional alfalfa used to feed dairy cows is very rich in protein, and while this seems like it would be an advantage for the animal, in fact, the opposite can be true,” Dixon says.
“Rapid degradation and fermentation of protein in the rumen causes bloating, which at worst can be lethal and also can mean that much of the potentially available protein is lost before it can be absorbed.”
As Dixon and Forage Genetics continued work on improved alfalfa, the company reached out to plant scientist Tom McCoy at Montana State University to join the team. McCoy became UNT’s vice president for research and economic development in 2013.
“The work Richard is doing is enhancing the feed value of a major forage crop,” McCoy says. “This will significantly benefit the dairy industry both in the United States and internationally.”
Mark McCaslin, CEO of Forage Genetics International, agrees.
“Richard was really able to see an idea, create a research project, and see it through while focusing on its direct impact to the cattle farming market,” McCaslin says.
Today, Forage Genetics has developed products that contain Dixon’s low-lignin alfalfa and are under review by the U.S. Department of Agriculture. They are expected to be available to growers and producers in the near future.
In addition to creating animal-friendly alfalfa, Dixon is looking for an alternative fuel source in another plant. Working with the U.S. Department of Energy’s BioEnergy Science Center, he is investigating how to develop liquid biofuels from genetically engineered switchgrass, an ideal plant for creating biofuel because it is high yielding and adaptable for growth in a wide area of the Southeast and Great Plains.
The challenge is that the sugars in switchgrass cell walls are less available for conversion to a liquid biofuel, like ethanol, than the sugars in corn kernels. Dixon’s group has been working to modify the chemical composition of the cell walls to make the sugars far more accessible — again through the modification of lignin.
“Moving ethanol away from a corn-based system is important to lessen the strain on the world’s food resources,” Dixon says
Dixon also is part of a research team exploring how grape seed compounds help prevent the development or delay the progression of Alzheimer’s disease in mice.
While current research shows that compounds from grape seed extract can slow the progression of the disease, scientists don’t know exactly why. Dixon is working with a research team at Mount Sinai School of Medicine in New York that hopes to identify what is happening in the brain in response to the compounds.
Having that information will allow scientists to explain, for the first time, how the compounds are affecting the development of the disease. Interestingly, the chemicals that appear to have protective effects against Alzheimer’s disease are related to the tannins in Dixon’s alfalfa research that protect ruminant animals from bloat.
“My mother suffered from Alzheimer’s disease in her later years, so this work is very important to me,” Dixon says. “The idea that we may find an answer to this devastating disease in plants, in a natural resource, is inspiring and is why I love plant science.”
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