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United States Department of Agriculture

Agricultural Research Service

Title: Mutations in a novel 9-stearoyl-ACP-desaturase gene are associated with enhanced stearic acid levels in soybean seeds

Authors
item Zhang, Ping - N.C. STATE UNIV
item Burton, Joseph
item Upchurch, Robert
item Shanklin, John - UPTON, NY
item Whittle, Edward - UPTON, NY
item Dewey, Ralph - N.C. STATE UNIV

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2008
Publication Date: November 24, 2008
Citation: Zhang, P., Burton, J.W., Upchurch, R.G., Shanklin, J., Whittle, E., Dewey, R. 2008. Mutations in a novel 9-stearoyl-ACP-desaturase gene are associated with enhanced stearic acid levels in soybean seeds. Crop Sci. 48:2305-2313.

Interpretive Summary: Stearic acid is typically not a major component of soybean oil as it accounts for only 2-4 % of the total fatty acid content. Soybean oil with increased stearic acid content would be beneficial because it would possess enhanced oxidative stability, would not require hydrogenation, and thus would not contain harmful trans fats. Although soybean germplasm lines with elevated stearic acid levels in the seed oil have been identified, the specific gene mutations responsible for this trait were not known. We have identified a new soybean gene, designated SACPD-C that encodes a '9-stearoyl-ACP-desaturase enzyme responsible for converting stearic acid to oleic acid. SACPD-C is detected and highly expressed only in developing seed tissue, suggesting that the encoded desaturase is the major contributor to oleic acid synthesis for seed storage lipid. The role of SACPD-C in storage lipid synthesis was further supported by the observation of mutations in this gene in two independent sources of elevated stearic acid in soybean germplasm, A6 (30% stearic acid) and FAM94-41 (9% stearic acid). A molecular marker diagnostic for the FAM94-41 SACPD-C gene mutation was strictly associated with the elevated seed stearic acid content in a segregating population, and could thus serve as a useful tool in the development of cultivars with oils possessing greater oxidative stability.

Technical Abstract: Stearic acid (18:0) is typically a minor component of soybean [Glycine max (L.) Merr.] oil, accounting for only 2-4 % of the total fatty acid content. Increasing stearic acid levels of soybean oil would lead to enhanced oxidative stability, potentially reducing the need for hydrogenation, a process leading to the formation of undesirable trans fatty acids. Although mutagenesis strategies have been successful in developing soybean germplasm with elevated 18:0 levels in the seed oil, the specific gene mutations responsible for this phenotype were not known. We have identified a new soybean gene, designated SACPD-C, that encodes a unique isoform of '9-stearoyl-ACP-desaturase, the enzyme responsible for converting stearic acid to oleic acid (18:1). High levels of SACPD-C transcript were only detected in developing seed tissue, suggesting that the encoded desaturase functions to enhance oleic acid biosynthetic capacity as the immature seed is actively engaged in triacylglycerol production and storage. The participation of SACPD-C in storage triacylglycerol synthesis was further supported by the observation of mutations in this gene in two independent sources of elevated 18:0 soybean germplasm, A6 (30% 18:0) and FAM94-41 (9% 18:0). A molecular marker diagnostic for the FAM94-41 SACPD-C gene mutation strictly associated with the elevated 18:0 phenotype in a segregating population, and could thus serve as a useful tool in the development of cultivars with oils possessing enhanced oxidative stability.

Last Modified: 12/18/2014
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