Gene Expression Profiles of Soybeans with Mid-Oleic Acid Seed Phenotype

Seeds of the mid-oleic acid soybean mutant M23 accumulate higher levels of oleic acid (50-60% oleate) by virtue of a deletion of GmFAD2-1A, an allele of the microsomal omega-6 oleate desaturase gene. In other less well characterized soybean varieties that are phenotypically mid-oleic, little is known about the expression levels of omega-6 desaturase GmFAD2 genes and other candidate genes that determine seed oleic acid content. We compared the steady-state transcript abundance during seed development of the oleate-ACP thioesterase (GmFATB1a), delta-9 stearoyl acyl carrier protein desaturase (GmSACPD) and the omega-6 fatty acid desaturase (GmFAD2) genes in five natural mid-oleic varieties and mutant M23 to gene expression data for the conventional non mid-oleic cultivar Dare. We found that, relative to Dare, there were instances where lower expression of GmFATB1a, GmFAD2-1A, GmFAD2-1B, GmFAD2-2, and GmFAD2-3 and higher expression of the GmSACPD-C might be associated with the mid-oleic seed phenotype. This finding suggests that of the several soybean genomic loci known or suspected to be involved in oleic acid phenotype, some are likely to encode genes involved in regulation of transcription of the oleate biosynthetic genes.