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Important Gene for Soybean Protein Content Found

When it comes to protein, soybean is the major supplier of this important component in both human and animal diets around the world. The U.S. normally produces about 1/3 of the world’s soybean tonnage, and the U.S. and Brazil together produce about 2/3 of the world’s soybeans.

A recent article in The Plant Journal (2022; DOI: 10.1111/tpj.15658) titled “Fine mapping and cloning of the major seed protein quantitative trait loci on soybean chromosome 20" provides information about a valuable finding regarding soy protein. After 30 years, scientists at the Univ. of Illinois have identified the gene that has the largest impact on the protein content of soybean seed. Soybean seeds normally contain around 40% protein, and this gene increases that about 2%, which is the most of any currently-mapped seed protein gene in the soybean genome. Since protein deficiency exists in many parts of the world, even this modest 2% protein increase in soybean seed would be important in helping to alleviate that deficiency. Other pertinent results from this research follow.

•    The specific gene, Glyma.20G85100 located on chromosome 20, is without a known function, but is closely related to the soybean plant’s “clock and circadian timing” genes.

•    Glyma.20G85100 comes in multiple forms, or alleles. Depending on the allele found in a particular soybean line, seed protein can be either high or low. Most commercial soybean lines contain the low-protein allele, apparently because the high-protein allele has a deleterious effect on yield. Thus, today’s elite varieties, which are bred for high yield, generally have the low-protein allele.

•    The high-protein allele affects the protein-coding region rather than the regulatory region of the gene.

•    The gene appears to be part of the soybean plant’s circadian timing, or the way the plant keeps track of processes such as time to maximize photosynthesis during the day and time to flower.

•    There is evidence that this gene impacts plant maturity in addition to protein and oil since lines homozygous for the high protein allele matured up to 5 days earlier than those homozygous for the alternative allele.

•    Results have shown that the gene impacts protein and oil across geographic/growing regions and genetic backgrounds. These effects are not necessarily associated with differences in maturity of soybean lines; however, further research is needed to improve the understanding of how this gene affects plant maturity and how this might be related to composition of the seed.

•    Identification of this gene could have a major effect on global food security by leading to breeding efforts that will result in increased protein level in soybean seed without a corresponding reduction in yield of this important crop.

•    An article titled “Gene important in soybean protein content found after 30-year search” by Lauren Quinn at the Univ. of Illinois provides additional information about this discovery, along with comments by co-authors of the journal article regarding the potential impact of the discovery.

•    Click here for a video that shows how the soy checkoff played a significant part in the discovery of this gene.

This, like many findings from complex research efforts, must be researched further to ensure it can be used on a broad scale by plant breeders to improve the value of soybean. Hopefully, the research outlined in the above-cited journal article will be followed by further efforts to ascertain just how this gene functions and how this knowledge can be applied to produce elite varieties that produce seed with a higher protein content.

Composed by Larry G. Heatherly, July 2022,