Location: Wheat, Sorghum and Forage ResearchTitle: Creation of a high-amylose durum wheat through mutagenesis of starch synthase II (SSIIa) Author
|Graybosch, Robert - Bob|
Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2013
Publication Date: 5/5/2013
Publication URL: http://handle.nal.usda.gov/10113/56425
Citation: Hogg, A.C., Gause, K., Hofer, P., Martin, J.M., Graybosch, R.A., Hansen, L.E., Giroux, M. 2013. Creation of a high-amylose durum wheat through mutagenesis of starch synthase II (SSIIa). Journal of Cereal Science. 57:377-383. Interpretive Summary: Obesity and associated health problems, including heart disease, stroke, high blood pressure and diabetes are reaching epidemic proportions in America. Diet and exercise are easy cures, but efforts to alleviate the problem would be aided by the availability of healthier versions of common components of the typical diet. Starch, provided by wheat-derived products including bread and pasta, contributes a significant number of calories. Typical wheat starch consists of approximately 25% amylose and 75% amylopectin. Both are polymers of the simple sugar glucose. In amylose, however, only straight chains exist, while amylopectin contains both straight and branched glucose chains. Amylose has the ability to form resistant starch, or starch that resists rapid degradation. Resistant starch acts in a manner similar to fiber, providing similar health benefits. Resistant starch also has a lower glycemic index than typical starch. This paper reports the development of durum wheat, through non-GMO methods, with higher starch amylose content. This successful project is the first step in the development of pasta and other durum wheat derived products with higher concentrations of resistant starch.
Technical Abstract: In cereal seeds mutations in one or more starch synthases lead to decreased amylopectin and increased amylose content. Here, the impact of starch synthase IIa (SSIIa or SGP-1) mutations upon durum starch was investigated. A screen of durum accessions identified two lines lacking SGP-A1, the A genome copy of SGP-1. The two lines were determined to carry a 29 bp deletion in the first exon of SSIIa. The SGP-A1 nulls were crossed with the durum variety ‘Mountrail’ and F5 derived SGP-A1 null progeny lines were treated with EMS. From each EMS population, one SGP-B1 null mutation was recovered with each being a missense mutation. Each of the SGP-1 nulls was found to have large increases in amylose content and reduced binding of SGP-2 and SGP-3 to the interior of starch granules. RNA-Seq was used to examine the impact the loss of SGP-1 has upon other starch biosynthetic genes. Significant increases in transcript levels of several starch biosynthetic genes were observed in SGP-1 nulls relative to Mountrail. The resultant high amylose durums may prove useful in the creation of value added pasta with increased firmness and reduced glycemic index.