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Research Highlights

Research Highlights
Investigation of Molecular Mechanism Underlying Negative Impact of a High-Protein Gene/Allele on Yield for Soybean Meal Quality Improvement

Figure 1. Functions of POWR1 gene in controlling seed protein, oil and yield and its uses in soybean protein improvement are being tested by engineering the gene in soybean.

By Charles An, Donald Danforth Plant Science Center

The global demand for soybean is driven by its highly valued oil, which has both dietary and industrial uses and by its high quality protein used primarily as animal feed. Approximately 60% of the value of soybean comes from meal, and about 40% from oil. Higher seed protein content is often negatively correlated with seed oil and yield. A century of soybean breeding in the U.S. has focused primarily on improving both yield and oil content, which is believed to have caused the seed protein content to decline significantly. In recent years, the protein content decease in some commercial soybean cultivars has become so severe that meal processors cannot meet the minimum protein content required for high-protein meal designation. Lower protein levels also put U.S. growers at a significant disadvantage in the international marketplace. 

This project aims to reverse this trend using the tools of molecular breeding and biotechnology. The long-term goals are to discover the genes that contribute to seed protein content decrease in soybean, to understand their underlying molecular and genetic basis, and to develop new breeding and biotech strategies, including gene editing, which will enable reversing the decreasing protein trend with no or minimal impact on yield and oil content. For the past several decades, soybean researchers have shown that there are more than 100 QTL (quantitative trait loci) that contribute to the protein content change in the soybean natural population. This project uses a big-data driven technology platform, integrating computer technology with soybean genetics, molecular biology and genomic approaches to identify genes associated with these QTLs.

An interdisciplinary technology platform, analyzing 1,500 soybean accessions and 15 terabytes of genetic data, enabled discovery of QTL gene candidates on both chromosome 20 and chromosome 15. A gene associated with high protein on chromosome 20 was identified as coding for a transcription factor — a protein that regulates many other genes. The chromosome 15 gene has been tentatively identified as well. Both genes need to be validated. In addition, a closely related gene to this transcriptional factor is on chromosome 10. 

Figure 2. Average protein content in soybean accessions containing low protein (LP) and high protein (HP) versions of SOP15 and POWR1 genes respectively. 

The functions of the gene on chromosome 20 in controlling seed oil, protein content and eventually seed yield are being investigated, using traditional and genetic engineering strategies to produce new high-protein soybean cultivars. Over 100 soybean plants containing modified genes were screened and analyzed. In addition, an in silico (computer-based) genotyping approach and a wet lab perfect DNA assay for the high protein allele/version of the gene was developed. This assay was used to screen 1,261 wild and cultivated soybean lines for the high protein allele. From this screen, 217 soybean accessions were identified as having the high-protein allele. 

The detailed knowledge being collected by this project about the protein QTL gene (candidate), the high-protein allele assay and the collection of high-protein soybean accessions will enable breeders to effectively integrate the high-protein trait into elite soybean cultivars, thus increasing the value of their soybean and making them competitive in the global marketplace. 

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.