Evolution of Carthamus species revealed through sequence analyses of the fad2 gene family

The diversity of 11 fatty acid desaturase (fad2) genes has not been investigated between cultivated and wild species in the Carthamus genus. In this study, 17 C. tinctorius accessions and 28 accessions from other Carthamus species were subjected to sequence analyses of this fad2 gene family. Results showed that among these genes, fad2-1 had a major role in the conversion of oleic acid to linoleic acid. Grouping of all studied wild polyploid species and the wild diploid C. leucocaulos suggested that C. lanatus transferred its fad2-1 gene to C. turkestanicus and C. lanatus. A phylogenetic tree based on fad2-1 gene sequences also showed that C. palaestinus and C. oxyacanthus grouped with C. tinctorius individuals, suggesting that C. tinctorius is closely related to both wild species. A one base pair deletion at position 604 in the fad2-1 gene coding region correlated with high levels of oleic acid content in five mutant phenotypes of the evaluated C. tinctorius accessions. Grouping of fad2-1 and fad2-8 (Ctfad2-10) indicated that both of these genes are involved in oleate desaturases activity. The fad2-3 (Ctfad2-3) and Ctfad2-4 had the highest sequence similarity among the other fad2 genes, indicating the conservative nature of these two genes among all the studied species. Our results suggest that C. lanatus is the likely progenitor of C. turkestanicus and C. creticus (Synonym C. baeticus). Also, C. palaestinus is genetically closer to C. tinctorius but the involvement of C. oxyacanthus cannot be excluded and, this requires further investigation.