Reference Genes and Expression Analysis of Seed Desaturases Genes in Soybean Mutant Accessions

Soybean oil is the second most-produced vegetable oil worldwide. To enhance the nutritional quality and oxidative stability of soybean oil, many soybean breeding programs are trying to increase oleic acid content and reduce linoleic and linolenic acid contents. The fatty acid profile of soybean oil is controlled by many genes, including those which code for omega-3 and omega-6 desaturases. Mutations in GmFAD2-1 and GmFAD3 genes are widely studied and their combinations can produce soybean oil with high oleic and low linoleic and linolenic content. However, few studies evaluate the effect of these mutations on gene expression. Therefore, the present study sought to identify reference genes, evaluate the expression of GmFAD2-1 and GmFAD3 seed desaturase genes in thirteen wild-type and mutated soybean accessions, and associate the expression patterns with fatty acid composition and with the GmFAD2-1 and GmFAD3 genotypes. GmCONS7 and GmUKN2 were identified as the best reference genes for combined use to normalize data. The GmFAD2-1A mutation of PI603452 accession was associated with a decrease in gene expression of GmFAD2-1A; however, downregulation may not be due to the truncated enzyme structure alone. These results suggested that there are factors other than GmFAD2-1A and GmFAD2-1B that have a considerable effect on oleic content, at least in soybeans with mutations in these two genes.