Lipid metabolites in seeds of diverse Gossypium accessions: Molecular identification of a high oleic mutant allele

Authors: STURTEVANT, DREW - University Of North Texas; HORN, PATRICK - University Of North Texas; KENNEDY, CHRISTOPHER - University Of North Texas; Hinze, Lori; Percy, Richard; CHAPMAN, KENT - University Of North Texas

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2016
Publication Date: 3/1/2017
Citation: Sturtevant, D., Horn, P., Kennedy, C., Hinze, L.L., Percy, R.G., Chapman, K. 2017. Lipid metabolites in seeds of diverse Gossypium accessions: Molecular identification of a high oleic mutant allele. Planta. 245:595-610.

Interpretive Summary: Although cotton is grown primarily for its fibers, the seed is an important global source of vegetable oil. Currently less than half of the seed produced in the United States is processed into vegetable oil, and with world demand for vegetable oils on the rise, this may represent an economical place for farmers to recognize additional value from their overall crop. Due to its stability and flavor enhancing properties, cottonseed oil is an excellent frying oil, but with changes to its fatty acid composition, cottonseed oil might enter other markets. The oil and fatty acid contents of cotton seed were measured, and images were taken to show the distribution of fatty acids in the seed. The presence of fatty acids and their amounts differed in various parts of the seed, and an allele corresponding to increased oleic acid was identified in one variety of cotton. With concerns expressed by some consumers about foods containing genetically modified organisms, there has been an interest to develop crops with altered seed oil compositions through breeding approaches rather than transgenic techniques. The success of the breeding approach relies, in part, on discovering existing variation in the seed fatty acid composition, such as the variety discovered here with increased oleic acid. There are likely many other interesting variations in fatty acids to be explored across the cotton germplasm collections, and our results highlight the value of detailed characterization that can lead to the discovery of important new traits. Since high-oleic seed oils have meant price premiums or increased market share for other oilseed crops, like sunflower, safflower, soybean, and corn, this variation in cotton may represent a potentially valuable association for cotton breeders to examine more closely.

Technical Abstract: The domestication and breeding of cotton for elite, high-fiber cultivars has led to reduced genetic variation of seed constituents within currently cultivated upland Cotton genotypes. However, a recent screen of the genetically diverse U.S. National Cotton Germplasm Collection identified Gossypium accessions/species with marked differences in seed oil and protein content. Here, several of these genotypes representing substantial variation in seed oil content were analyzed for quantitative and spatial differences in lipid compositions by mass spectrometric approaches. Results indicated considerable variation in pathway metabolites for triacylglycerol biosynthesis in embryos across Gossypium species, suggesting that this variation might be exploited by breeders for seed composition traits. By way of example, these lipid metabolite differences led to the identification of a mutant allele of the D-genome homeologue of the delta-12 desaturase (fad2-1D-1) in a wild accession of G. barbadense that has a high oil and high oleic seed phenotype. This mutation is a ~90-bp insertion in the 3' end of the FAD2-1 coding sequence leading to the introduction of a premature stop codon. Given the large amounts of cottonseed produced in the U.S. that is currently not processed into higher value products, these efforts might be one avenue to raise the overall value of the cotton crop for producers.