Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/18/2003
Publication Date: 11/1/2003
Citation: BILYEU, K.D., PALAVALLI, L.H., SLEPER, D.A., BEUSELINCK, P.R. THREE MICROSOMAL OMEGA-3 FATTY ACID DESATURASE GENES CONTRIBUTE TO SOYBEAN LINOLENIC ACID LEVELS. CROP SCIENCE. 2003. V. 43(6). p. 1833-1838. Interpretive Summary: The flavor and shelf life of soybean oil can be improved by reducing the amount of linolenic acid in the oil. Multiple genes control linolenic acid production in soybean, but it is difficult for plant breeders to determine the contribution of each gene to lowered linolenic acid. The objective of this study was to identify and characterize the family of soybean omega-3-fatty acid desaturase genes and link them to low seed linolenic acid to develop molecular markers that can be used by soybean plant breeders to efficiently identify desirable genotypes. We performed database searches to identify three soybean fatty acid desaturase genes that contribute to linolenic acid levels in soybean seed. The three soybean fatty acid desaturase genes were cloned and characterized. Once the genes were identified and cloned, we examined soybean lines for the presence or absence of the genes. One of the three genes was predominantly expressed in developing seeds. Some low linolenic acid breeding lines contained more than one of the genes. This information will be important to plant breeders in their attempts to alter amounts of linolenic acid in soybean seed by identifying desirable molecular markers in important breeding lines and their offspring.
Technical Abstract: Three independent genetic loci have been shown to contribute to soybean (Glycine max L.) seed linolenic acid levels, including the well-characterized Fan locus. Linolenic acid is the product of omega-3-fatty acid desaturase enzyme activity. The objective of this study was to identify and characterize the family of soybean omega-3-fatty acid desaturase genes and link them to low seed linolenic acid as a tool for the development of molecular markers for low linolenic acid soybean. Using database homology searches and gene cloning, three soybean microsomal omega-3-fatty acid desaturase genes that contribute to seed linolenic acid levels were identified and characterized. Relative expression was characterized by quantitative real-time RT-PCR (reverse transcriptase polymerase chain reaction). One of the three genes was predominantly expressed in developing seeds. We determined that the low linolenic acid breeding line A5 (fan fan) contains two of the genes, but is missing the third sequence. Therefore, the Fan locus can be definitively assigned to one of the three microsomal omega fatty acid desaturase genes present in the soybean genome. Molecular markers for defects in the three genes will enhance soybean programs breeding for low linolenic acid.