F3'5'H是催化合成飞燕草色素的关键酶。不同来源F3'5'H的催化能力差别较大。研究发现F3'5'H序列中一段编码9个氨基酸的特殊结构可能与催化合成更多的飞燕草色素有关，但其作用机制尚不明确。我们已克隆的中国桔梗PgF3'5'H也具有此特殊序列结构。本研究拟通过定点突变技术去除PgF3'5'H蛋白序列中的特殊结构获得其突变型基因；利用电转化和农杆菌介导法将野生型基因及其突变型同时转化酵母和烟草；通过Q-PCR分析野生型基因及其突变型在酵母和烟草中的基因表达量；利用SDS-PAGE检测野生型基因及其突变型在酵母中的目的蛋白合成量；通过HPLC鉴定野生型基因及其突变型在酵母和烟草中分别催化合成的新物质及花色素的成分和含量，比较二者的底物特异性及酶活性的差异。从而分析PgF3'5'H特殊序列结构的催化功能，推测其作用机制。为观赏植物蓝色花色形成机制研究及花色分子育种工作提供一定理论依据。

Favonoid 3’,5’-hydroxylases (F3'5'H) is a key enzyme for biosynthesis of the delphinidin pigments. The differences of the F3'5'Hs activity were significant due to sequence differences. The available research suggested that a unique primary structure of F3'5'H might be conferred high competence in the accumulation of delphinidin derivatives, but its mechanism remains unclear. The same special sequence structure was also found in the Platycodon grandiflorum PgF3'5'H by us. In this study, the mutant PgF3'5'H gene will be obtained by site-directed mutagenesis, and then the wild type PgF3'5'H gene and its mutant will be transformed into yeast and tobacco to identify the genes expression and proteins synthesis by Q-PCR and SDS-PAGE, respectively. The composition and content of the target proteins and anthocyanidins will be detected in yeast and tobacco by HPLC to compare the differences of the substrate specificity and enzymatic activity of the PgF3'5'H and its mutant gene. The functions of the PgF3'5'H and its special sequence structure will be verified, and the action mechanism will be speculated. These results will provide some theoretical basis and research foundation for studying the biosynthesis mechanism of the blue anthocyanin pigments and for the molecular breeding of the blue ornamental plants.