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Research Highlights
Increasing Soybean Oil Yield Through Targeted Gene Silencing and Overexpression

By Jay Thelen, Ph.D., University of Missouri

Consumer demand for vegetable oils has steadily increased worldwide for the past four decades, mainly due to their versatility. Soybeans are of the major sources of vegetable oils in the U.S., but with a lower oil content than most oilseed crops (16-22% of dry weight). Increasing oil content without losing protein content would increase overall seed yield and value. To do this, the first rate-limiting step in oil biosynthesis has been targeted. It is catalyzed by acetyl-CoA carboxylase (ACCase), which can be manipulated to push more of the plant’s carbon into oil biosynthesis.

Figure 1. Reducing the level BADC protein in developing soybean seeds is hypothesized to increase ACCase activity, resulting in more seed oil production. BADC usually competes with BCCP, a required ACCase subunit, limiting activity of the enzyme.

Two populations of soybeans have been developed that contain increased levels of ACCase. The first has a repressed negative regulator of ACCase called biotin/lipoyl attachment domain containing protein (BADC), and the second has overexpressed a limiting subunit of ACCase called alpha-carboxyltransferase (-CT). These same variants produced seeds with higher oil content in both Arabidopsis thaliana and Camelina sativa, an oilseed cover crop. In Arabidopsis, oil content increased between 10% and 30%. 

The next step was to develop soybean seed for enhanced ACCase, in order to increase oil production in seeds without doing so elsewhere in the plant, which may have negative effects on growth. Soybeans are currently being propagated to trait stability and highest oil content, and promising lines are being identified. Field trials and full phenotypic characterization are planned as the next steps in this $95,286 project. 

Figure 2. Increasing expression of α-CT (the limiting ACCase subunity) is hypothesized to increase assembly of functional ACCase, resulting in higher seed oil production.

This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.