pCtFSG2, a flower-specific promoter with suitable promoter activity in safflower

Safflower ( Carthamus tincorius L.) is an economically important plant. Flowers are a source of dyes and active ingredients in medicines. The development of flower-specific promoters is of great significance for the directed regulation of the biosynthesis of targeted products. However, few flower-specific promoters have been reported in safflower. In this study, transcriptome analysis of various safflower tissues was performed. A total of 40.37 Gb of clean data were obtained, and 100 safflower-specific genes were screened. Three genes ( CtFSG1 , CtFSG2 and CtFSG3 ) were identified by RT–PCR, and all had high expression in flowers. The promoters of the three genes ( pCtFSG1 , pCtFSG2 and pCtFSG3 ) were cloned, and the promoter sequences were analysed. Promoter activity analysis showed that pCtFSG2 had suitable promoter activity in protoplasts of tubiform floret in safflower. This promoter specificity was further characterized by Agrobacterium-mediated transformation of pCtFSG2::GUS to Arabidopsis thaliana . The results showed that GUS staining was detectable only in flowers. Moreover, deletion analysis of the pCtFSG2 promoter region revealed that the DNA segments from − 1953 to − 1534 and − 980 to − 490 are critical for the expression of pCtFSG2 . Our results indicated that pCtFSG2 is a flower-specific promoter with suitable promoter activity in safflower, which has potential value for directional modification of safflower.