At the root of a thriving U.S. bioeconomy is development of better plants—living factories that anchor the economy against global shocks and strengthen domestic supply chains by providing the feedstock for new fuels, chemicals and materials.
It is a complex challenge to develop and field test bioenergy plants such as the poplar tree, engineered to grow larger while resisting drought and disease. The Department of Energy’s Oak Ridge National Laboratory is an internationally recognized leader in plant transformation, accelerating this process with a continual stream of discoveries, many of them licensed and adopted by industry.
ORNL scientists have a history of breakthroughs in plant science, from leading the sequencing of the first tree genome to producing the first-ever, integrated dataset of poplar variants and their microbiomes to the extensive portfolio of patented innovations and high-impact publications from the ORNL-led Center for Bioenergy Innovation, or CBI.
ORNL’s successes are the result of what DOE national laboratories do best: bringing together scientists from multiple fields—in this case plant biology, genomics, computational science and AI, synthetic biology, chemistry, neutron science and materials science—to ensure U.S. competitiveness and prosperity through transformative science and technology solutions. Read on to learn about five ways ORNL is creating better feedstock crops.
1) Developing larger plants with higher yield
ORNL scientists working within CBI discovered the photosynthesis-enhancing Booster gene in a native poplar tree, a conserved gene that helps poplar adapt to changing conditions. Hybrid poplars engineered with Booster grew as much as 200% taller in greenhouse conditions, and up to 37% taller in the field. The hybrids also had 88% more stem volume, increasing biomass per plant. Comparable results were found in other plants augmented with the gene, suggesting Booster could similarly enhance food crops and help resolve food security challenges.
Scientists discovered another gene, REVEILLE1, in the agave plant that regulates when plants go dormant and when they begin budding. Poplar trees enhanced with the gene nearly doubled in size, with biomass rising by 166% when grown in a greenhouse, yielding taller trees with larger leaves and thicker stems compared with standard poplar. Scientists used the gene to repress a portion of the tree’s dormancy over two winters, extending the plant’s growing season.
Researchers at ORNL developed a first-ever method of detecting RNA inside plant cells using a visible fluorescent signal. The technology lets researchers detect and track changes in RNA and gene expression in real time, providing a powerful tool for the development of hardier bioenergy and food crops and for detection of unwanted plant modifications, pathogens and pests. Watch video
Easy detection of CRISPR-enabled genome editing in plants was the driver behind another ORNL invention, a system that reveals CRISPR activity in plants using a reporter protein that results in a fluorescent signal detected by an ordinary UV flashlight. The method, much as the RNA detection process, replaces a traditional time-consuming and laborious forensic method of detecting such activity. The technique, demonstrated in several plant species, also accelerates progress on development of hardy bioenergy crops by confirming successful CRISPR-assisted gene editing to trigger desired traits in plants, improving the security of next-generation biotechnologies.
3) Building plant resilience
In the search for genes that would give plants the ability to tolerate stressful conditions like drought and water with high salt content, ORNL scientists turned to desert plants such as kalanchoe and agave. They discovered a family of genes regulating a type of photosynthesis called crassulacean acid metabolism, or CAM, that triggers a behavior in which plants only open their stomata, or leaf pores, at night to capture carbon dioxide from the air, while keeping them closed and conserving water during the hotter daylight hours. In follow-on research, the scientists discovered a single gene controlling CAM plant growth and stress tolerance. The gene boosts plant growth and stimulates the production of an amino acid known to increase stress tolerance.
Much as in human health, scientists have for years known that a healthy microbiome is essential to plant health. With support from CBI and the DOE Plant-Microbe Interfaces Science Focus Area at ORNL, scientists discovered the gene controlling an important plant-fungal relationship, and successfully stimulated the symbiosis in a plant that typically resists it. The beneficial symbiosis between a plant and the fungus Laccaria bicolor resulted in a fungal sheath that envelops the plant’s roots and extends far from it, spurring better nutrient uptake and resistance to drought and disease. The discovery enables development of crops that can withstand harsh growing conditions, require less chemical fertilizer and produce more plentiful plants per acre.
4) Designing plants with purpose
A successful bioeconomy hinges on harnessing the natural abundance of polymers in plants, turning cellulose, lignin and starch into valuable fuels and products. Lignin, for instance, gives plants their rigidity and is a good source of the building blocks and chemical compounds needed for biofuels. But lignin is also hard to break down. CBI scientists studying plant polymers discovered that a form of lignin called C-lignin is easier to deconstruct — and they found the genetic mechanism at play in C-lignin’s formation. The scientists studied the cleome plant and how it switches to C-lignin formation as it grows and pollinates, with molecular-level analysis. By introducing C-lignin into feedstock plants, scientists can reduce the energy requirements for biomass deconstruction.
In another project, researchers used large-scale poplar datasets and ORNL’s supercomputing resources to quickly identify key genes and networks involved in formation of lignin. The project mined information from 409 poplar genotypes on gene activity, genetic variations and chemical modifications, uncovering genes that likely play key roles in building and regulating the tree’s cell walls. The study provided key insights into the molecular mechanism of lignin formation and provided new gene targets for future improvements in poplar.
5) Accelerating new hybrids
With successive discoveries of new gene-to-trait linkages under their belt, ORNL scientists have set to work creating faster ways of developing new plant varieties. One recent breakthrough came in the form of a “gene-stacking” invention, in which ORNL scientists developed a process to insert multiple genes into plants in a single step. Having the ability to test multiple genes simultaneously replaced the painstaking method of inserting one gene at a time into DNA and then sequencing the plant. Using the R&D 100 award-winning method, researchers simultaneously inserted four genes into plants in the initial project. ORNL scientists have since transformed plants with 10 genes at once, and are aiming for more.
ORNL is also developing AI-enabled systems of the future to advance crop science. The future is now in ORNL’s Advanced Plant Phenotyping Laboratory, or APPL, where scientists are utilizing robotics, best-of-class imaging systems, AI and machine learning to speed the discovery of new gene-to-trait linkages, quickly analyze new plant hybrids, and explore how beneficial microorganisms directly affect plant health and stress tolerance. APPL quickly gathers data on key factors in plant development such as photosynthesis efficiency, growth, water use, stress response and biochemical composition, measuring changes in plants before they’re visible to the human eye. Capturing data in near-real-time gives the ability to quickly confirm what’s working and what’s not. APPL allows research teams to uncover critical insights into plant genetics and performance, ushering in the next generation of breakthroughs for better crops.
Many of the discoveries were accomplished with the sustained support of the DOE Office of Science Biological and Environmental Research program.
UT-Battelle manages ORNL for DOE’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. — Stephanie Seay