Technical Abstract: Stearoyl-acyl carrier protein-desaturase, omega-6 desaturase, and omega-3 fatty acid desaturase genes are present as multiple copies in the soybean genome as expected given the evidence from cytogenetics, genetic mapping, and genomic sequencing that soybean is a paleopolyploid species that underwent at least two major genome duplications. The soybean genome possesses tissue-specific alleles for all three of these major C18 desaturase enzymes that are involved in the biosynthesis of triacylglycerols. The occurrence of seed-specific alleles of these genes provides for the accommodation of the great increase in lipid biosynthesis that occurs as the developing soybean seed produce storage lipid reserves. The C18 fatty acid composition (that is the relative levels of unsaturated fatty acids in tissue lipids) of soybean and other plants can change in response to environmental temperature changes (a global climate change factor), infection by pathogens, other stresses, and the intervention of humans (geneticists). This is important because fatty acids and fatty acid-derived signals activate components of pathogen defense pathways. Current evidence indicates that fatty acid desaturases in soybean are regulated by mechanisms of transcription control, post-translational enzyme stability, and enzyme activity modulation. Genomic analysis of gene loci and gene flanking regions using the Williams 82 soybean genome database and gene expression analyses will greatly expand our knowledge of soybean gene regulatory sequences and their interaction with transcription complexes. Continued development of soybean SNP markers, mapping and dissection of Quantitative Trait Loci and gene silencing analyses will lead to the discovery of new genes involved in fatty acid biosynthesis and regulation, abiotic and biotic stress acclimation, and will help uncover potential epigenetic interactions among them.