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

MAIN CONCLUSION: Genetically diverse cottonseeds show altered compositions and spatial distributions of phosphatidylcholines and triacylglycerols. Lipidomics profiling led to the discovery of a novel FAD2 - 1 allele, fad2 - 1D - 1 , resulting in a high oleic phenotype. The domestication and breeding of cotton for elite, high-fiber cultivars have led to reduced 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 with marked differences in seed oil and protein content. Here, several of these accessions representing substantial variation in seed oil content were analyzed for quantitative and spatial differences in lipid compositions by mass spectrometric approaches. Results indicate considerable variation in amount and spatial distribution of pathway metabolites for triacylglycerol biosynthesis in embryos across Gossypium accessions, 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-subgenome homolog 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 FAD2-1D coding sequence and a modification of the 3' end of the gene beyond the coding sequence leading to the introduction of a premature stop codon. Given the large amounts of cottonseed produced around the world 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.