Isolation and analysis of flavonoid 3'-hydroxylase (F3'H) genes from cyclamen 'Strauss'

Anthocyanins are the most abundant and primary flavonoid pigments, which produce a wide range of colors. Flavonoid 3’-hydroxylase (F3’H) is one of the key enzymes in anthocyanin biosynthesis and has been identified from a variety of ornamental plants. For isolating and charactering the anthocyanin related F3’H in cyclamen, three candidates of F3’Hs named as STRF3’H1, STRF3’H2a and STRF3’H2b were obtained from petals of Cyclamen persicum cultivar ‘Strauss’ (STR). Phylogenetic analysis and sequence alignment suggested that these putative STRF3’Hs belong to the CYB75B class of cytochrome P450 superfamily, containing the unique conserved motifs of F3’H enzyme. The prediction of transmembrane structure showed that STRF3’H2a and STRF3’H2b each had a transmembrane region, while F3’H1 did not. STR and the wild Cyclamen persicum (C. persicum), have different major anthocyanin components in petals. Since the synthesis of major anthocyanins in C. persicum and STR are closely related to F3’H and flavonoid 3’,5’-hydroxylase (F3’5’H), the expression of these genes had been compared by real-time PCR. F3’Hs were expressed strongly in STR, weakly in C. persicum, while F3’5’H was opposite. The results implied F3’H is likely taking an active role in pigmentation in STR. The function will be further analyzed to verify the relevance between F3’H and STR flower color formation.