Cloning and Molecular Identification of A Fatty Acid Desaturase 2 Gene in a and C Genome of Brassica Species

The fatty acid desaturase 2 (fad2) gene was proven to be a major locus for high oleic acid (C18:1). Brassica napus is an amphidiploid species originating from a spontaneous hybridization of Brassica rapa and Brassica oleracea. B. napus contains multiple copies in genome for most of the genes, including fad2 genes. The research cloned nine fad2 genes from 3 varieties of B. rapa and 3 varieties of B. oleracea, respectively. Alignment of the nine fad2 sequences from B. rapa and B. oleracea detect-ed 6 single nucleotide polymorphic sites, which resulted in 6 amino-acid substitutions. The nucleotide substitutions at position 743 bp in the fad2-A gene and position 947 bp in the fad2-C gene were used as 3’ end of al ele-specific primers. In use of the al-lele-specific primers to amplify fad2 gene, we could identify if the fad2 gene originated from A genome or C genome. Besides, the research found that fad2 genes in C genome are more conserved in evolutionary process than those in A genome. The fad2 expression data reported in this study revealed that fad2-A from B. rapa was not only expressed in siliques same as fad2-C from B. oleracea, but also expressed in a high level in stems. Not even the less, fad2 gene from B. napus was expressed higher in roots and flowers. Al these results provided evidences that fad2, though it was expressed differently in B. rapa and B. oleracea, but it was regulated by the same approach in B. napus.