Mizzou researchers engineer plants for optimal biofuel production

Arabidopsis may seem like a simple plant but at the University of Missouri plant biochemist Jay Thelen is using it as a powerful model to explore ways to boost oil production—an important step toward creating more sustainable, plant-based energy sources. 

To meet the increasing global demand for biofuels, scientists are already modifying plant genes to boost the amount of plant oil being produced.  

That’s because inside the plant, a complex network of metabolic pathways turns sunlight, carbon dioxide (or atmospheric carbon), water and nutrients into vital compounds including oil, the foundational ingredient of biofuel. 

Genes give instructions to enzymes, and, in turn, those enzymes help control the plant’s metabolic pathways.  

But we are only beginning to understand how modifying these genes to produce more oil affects the plant’s other metabolic pathways, which are all interconnected. 

In their new study, Thelen and his colleagues have charted how plant metabolism responds to these genetic changes.  

Their findings will provide fellow scientists with clues for how to tweak a plant’s oil production to create the maximum amount of biofuel. 

“Because oil production utilizes central metabolic pathways, we know that engineering plants to produce more oil ultimately impacts other pathways—creating constraints on carbon supply,” said Thelen, professor of biochemistry in Mizzou’s College of Agriculture, Food and Natural Resources. “By using the knowledge we gained in this large-scale biological study, we can identify these metabolic bottlenecks and release these constraints through targeted engineering in order to maximize desirable products, such as oil.” 

Surprising findings 

One of the study’s most unexpected findings challenged a long-held observation that oil content in seeds is inversely proportional to protein.  

In other words, if you try to increase oil, protein goes down and vice versa.  

However, Thelen and colleagues found simultaneous increases in both oil and protein content in the seeds. 

“The surprising co-increase in protein suggests that it might be possible to simultaneously enhance multiple valuable components within plants that are grown for both oil and protein traits, rather than being forced into a trade-off,” Thelen said. “This study of a gene knockout for a regulatory gene for fatty-acid production could offer clues for the engineering of seeds with a higher overall content of desirable substances, offering greater value.” 

Another unexpected result revealed an energy-wasting “futile cycle.”  

Even as the genetically modified plants made more oil, they also triggered processes that broke those oils down. 

“We noticed that the plants upregulated pathways for lipid mobilization, seemingly breaking down the lipids (fatty acids) they were trying to overproduce,” he said. “In future research, we want to try to discover what caused this unusual metabolic response, and ultimately slow down fatty-acid catabolism to minimize this wasteful cycle.” 

Maximizing efficiency 

The team’s long-term goal is to help develop more efficient oil-producing plants such as camelina and pennycress—fast-growing cover crops—to quickly absorb carbon dioxide and turn it into oil in the most efficient way possible. 

“This carbon dioxide can be put into various products, such as simple and complex sugars, waxes, organic acids and oils,” said Thelen, who is also a principal investigator in the Christopher S. Bond Life Sciences Center. “The goal of genetic engineering is to move as much of that carbon from those less-valuable products into creating seed oil, the principal agronomic product for oilseed cover crops.”