Isolation and expression analysis of six putative structural genes involved in anthocyanin biosynthesis in Tulipa fosteriana

Getting basic molecular information of pigment formation in tulip flower is a prerequisite for enhancing the range of flower colors. In this study, six cDNA clones encoding putative anthocyanin biosynthesis enzymes were isolated from petals of tulip (Tulipa fosteriana) ‘Shangnong Zaoxia’ by rapid-amplification of cDNA ends (RACE): chalcone synthase (TfCHS1), chalcone isomerase (TfCHI1), flavanone 3-hydroxylase (TfF3H1), flavonoid 3′-hydroxylase (TfF3′H1), dihydroflavonol 4-reductase (TfDFR1) and anthocyanidin synthase (TfANS1). Southern blot analysis showed they all present as multiple copies in the tulip genome. In parallel, the expression profiles of these genes in different tulip tissues as well as in petals during flower development were measured by real-time quantitative PCR. The expression levels of TfCHS1, TfCHI1 and TfF3H1 were higher in stems and leaves than those in floral tissues (stamens, pistils, petals), the expression of TfF3′H1, TfDFR1 and TfANS1 showed highest levels in petals compared with other tissues. During flower development, the transcript levels of TfCHS1 and TfF3H1 were continuously increased, which were in general constant with the changing pattern of anthocyanin accumulation; the mRNA levels of TfDFR1 and TfANS1 and anthocyanin accumulation were both significantly increased; a low level transcript of TfF3′H1 was detected in petals throughout pigmentation process; TfCHI1 expression level firstly dramatically decreased and then gently increased. These results suggest that the red pigment accumulation in petals of T. fosteriana was positively related to the expression levels of TfCHS1, TfF3H1, TfDFR1 and TfANS1.

► Isolated cDNAs of TfCHS, TfCHI, TfF3H, TfF3′H, TfDFR and TfANS from tulip.
► All isolated genes were present as multiple copies in the tulip genome.
► Isolated genes were differentially expressed in stem, leaf, petal, stamen and pistil.
► TfCHS, TfF3H, TfDFR, TfANS were correlated to the anthocyanin accumulation in petal.