Engineering Denser Plants For Biofuel

plant stems showing results of genetic modification producing more lignin and cellulose
The stem on the right is from a plant with a newly discovered gene removed, producing more lignin.

Scientists at The Samuel Roberts Noble Foundation have uncovered a gene responsible for controlling key growth characteristics in plants, specifically the density of plant material. Denser plants have more biomass without increasing the agricultural footprint, meaning farmers and ranchers can produce more plant material from the same sized field. Plants that have increased density hold great potential to be used to produce biofuel, electricity, and even advanced materials, like carbon fiber.

“This is a significant breakthrough for those developing improved plants to address pressing societal needs,” said Richard Dixon, D. Phil., director of the Noble Foundation’s Plant Biology Division. “This discovery opens up new possibilities for harnessing and increasing the potential of crops by expanding their ranges of use. These plants will be part of the next generation of agriculture which not only impacts food, but many other vital industries as well.”

Huanzhong Wang, Ph.D., a postdoctoral fellow in Dixon’s lab, found a gene that controls the production of lignin in the central portions of the stems of Arabidopsis and Medicago truncatula, species commonly used as models for the study of plant genetic processes. Lignin is a compound that helps provide strength to plant cell walls, basically giving the plant the ability to stand upright. When the newly discovered gene is removed, there is a dramatic increase in the production of biomass, including lignin, throughout the stem.

Research targeting plants that are grazed by animals has historically focused on reducing lignin production within the plant. However, increasing lignin in non-food crops, such as switchgrass, may be desirable for increasing the density of the biomass and producing more feedstock per plant and, therefore, more per acre.

“In switchgrass, as the plant matures, the stem becomes hollow like bamboo,” Dixon said. “Imagine if you use this discovery to fill that hollow portion with lignin. The potential increase in biomass in these new plants could be dramatic. This technology could make plants better suited to serve as renewable energy sources or as renewable feedstocks to produce advanced composite materials that consumers depend on every day.”

Additionally, further research with collaborators at the University of Georgia revealed that removal of the gene also can increase the production of carbohydrate-rich cellulose and hemicellulose material in portions of the plant stem. These are the components of a plant that are converted to sugars to create advanced biofuels, such as cellulosic-derived ethanol or butanol. More celluloses and hemicelluloses mean more sugars to use for carbohydrate-based energy production.

“Science often progresses in increments,” Dixon said. “Every once in a while, though, you have a significant breakthrough that helps redefine the research. This is certainly one of those moments for our advanced feedstock program.”

This project is supported by the United States Department of Energy and the Oklahoma Bioenergy Center. It builds upon decades of research by Dixon’s group, which has already demonstrated the ability to reduce lignin in plants as well as modify its composition and characteristics.

The potential lies in the combination of these current and past discoveries to maximize the usefulness of agricultural crops; achieve more from less through the application of technology; and design agricultural feedstocks to produce sustainable sources for energy and other valuable industrial products.

This research was recently published in Proceedings of the National Academy of Sciences (PNAS) as well as selected as an Editors’ Choice feature in Science. Since its establishment in 1914, PNAS is one of the world’s most cited, multidisciplinary scientific serials that publishes cutting-edge research reports, commentaries, reviews, and perspectives. Science is regarded as the world’s leading journal for original scientific research, global news, and commentary.

The Samuel Roberts Noble Foundation, headquartered in Ardmore, Oklahoma, is a nonprofit organization conducting agricultural, forage improvement and plant biology research; assisting farmers and ranchers through educational and consultative agricultural programs; and providing grants to nonprofit charitable, educational and health organizations.

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