Sequence variations and expression analysis of FAD2 gene among safflower materials with different linoleic acid content in seed oil

Safflower varieties were commonly divided into high, low and middle linoleic acid (LA) types according to their LA relative percentage contents in the seed oil. Fatty acid desaturase 2 (FAD2) plays a key role for LA content in seed. The sequence variations of FAD2 (CtFAD2-2, CtFAD2-10, CtFAD2-11) genes which could express in developmental seed of safflower were analyzed in 15 different LA-type materials. The results revealed that the CtFAD2-2 sequences were the same in all materials, and the CtFAD2-10, CtFAD2-11 sequences formed into two haplotypes independent of the LA-type of safflower seed. Yeast expression analysis revealed that two haplotypes of CtFAD2-10 had the function of oleic acid desaturase. The real-time PCR analysis of FAD2 in high and low LA-type materials at different seed developmental stages revealed that CtFAD2-2, CtFAD2-10 and CtFAD2-11 expressed mainly at 10 days after flower (DAF) for two different LA-type materials and the accumulation of few mRNA was detected in 14–22 DAF. The expression pattern of CtFAD2-1 in two different LA-type safflower materials was significantly divergent. For high-LA type, the accumulation of CtFAD2-1 mRNA was extremely low in 10 DAF, and its expression level increased sharply between 14 and 18 DAF and decreased slightly after 18 DAF. For low-LA type, the accumulation of CtFAD2-1 mRNA was extremely low during seed development stages. In conclusion, the gene structure and expression level of CtFAD2-1 may be the main factor affecting the differentiation of LA-type for safflower materials.