Research HighlightsImproving Soybean Transportation — Within the Plant — for Higher Protein
Highlights:
- In soybeans, nitrogen production links to protein concentration.
- Unique research at the University of Tennessee looked at transportation genes within soybeans to boost protein content.
- Results indicate that breeding soybeans to transport more N from roots to maturing seeds has potential to increase protein content in U.S. soybeans.
By Laura Temple
Moving soybeans from fields to storage to customers requires efficient, abundant transportation methods. Trucks. Trains. Barges. The strong transportation network is one advantage of U.S. Soy.
A different kind of efficient, abundant transportation could be a key to creating another advantage for U.S. Soy: improved protein content.
Tarek Hewezi, professor of plant molecular biology at the University of Tennessee, is taking a unique approach to enhancing soybean yield and seed quality. A Tennessee Soybean Promotion Board investment funds his research.
“In soybeans, nitrogen fixation links to yield and seed protein content,” he explains.
Soybean roots develop nodules with bacteria that convert N into a form the plant can use. The conventional breeding approach to improving N production and use in soybeans has been to focus on genes tied to root nodulation and N-fixation.
“We looked at how nitrogen, amino acids and other micronutrients move from soybean roots to the rest of the plant, especially the seeds,” Hewezi says. “We wanted to learn if moving more nitrogen would impact protein content.”
Rather than increase N production, his goal was to learn if soybeans could use the N they fix more efficiently by getting more of the nutrient to maturing seeds.
Boosting Nitrogen and Microelement Movement
Hewezi identified three transporter genes in soybeans. These genes code instructions for proteins that help molecules move across cell membranes. That’s how N, sugar, amino acids, water and other nutrients move upward from plant roots, through stems and shoots, to leaves and seeds.
He modified plants to overexpress these transporter genes to encourage more N and microelements to be delivered to maturing soybean pods. To do this, his team used transgenics to introduce the overexpressed genes into soybean plants, causing test plants to activate those genes and increase the number of nitrogen-fixing nodules. This could be compared to increasing the number of train cars or barges to move more soybeans more efficiently.
Then he compared nitrogen content, protein concentration and other characteristics from the modified soybeans to normal control plants.
“The soybeans with overexpressed transporter genes had higher protein content,” Hewezi reports. “They met or exceeded the standard for soybean meal with 47.5% protein content.”
He believes breeding with a focus on intra-plant transportation has the potential to address the documented decline in protein concentration from U.S. Soy.
“In our trials, soybeans modified to over-express transporter genes outperformed the protein content from top performing varieties in Brazil,” he says. “U.S. Soy can match or exceed the standards for high protein meal with transporter genes.”
Additional Resources
Breeding Research Lays Foundation to Investigate Links Between Fixing Nitrogen and Protein Concentration – SRIN article
Development of High-Yielding, High-Protein Germplasm by Enhancing Nitrogen Acquisition and Its Transport to Seed – SRIN article
Improving Roots Improves Soybean Yields – SRIN article
Meet the Researcher: Tarek Hewezi – SRIN profile | University profile
Published: Aug 18, 2025
The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.
