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黄烷酮-3-羟化酶(F3H)是黄酮类化合物合成途径的关键酶之一,其催化黄烷酮合成的二氢黄酮醇又可经不同代谢途径合成花青素等多种黄酮类物质.以鲁桑(Morus multicaulis)品种育711号植株的幼叶cDNA为模板,利用RT-PCR和RACE技术克隆了桑树F3H基因cDNA的全长序列,将该基因命名为MmF3H(GenBank登录号:KU301748).该基因开放阅读框(0RF)长1 095 bp,编码一个含有365个氨基酸残基的多肽,预测蛋白质分子质量为40.15 kD,等电点为4.93.该基因编码氨基酸序列与川桑(Morus notabilis)F3H的序列相似度高达98％,与其它5种植物F3H也具有较高的序列相似度(79％～82％),说明F3H基因编码的氨基酸序列具有较高的保守性;系统进化树也显示来自鲁桑的F3H序列与来自川桑的F3H序列聚在一枝,亲缘关系最近.qRT-PCR检测MmF3H基因在35份桑种质资源植株幼叶中的表达水平存在较大差异,相对表达量较高的达到0.784 5,而较低的仅为0.012 1;用分光光度法测定35份桑种质资源植株桑叶片中的总黄酮和总花青素含量也存在较大差异,而且总黄酮含量的差异与MmF3H基因表达水平的差异具有一定相关性,推测MmF3H催化生成的产物属于黄酮类化合物合成途径的上游产物.“,”Flavanone-3-hydroxylase (F3H) is one of the key enzymes in flavonoid biosynthetic pathway.F3H catalyzes the reaction of flavanone to form dihydroflavonol which is then used to synthesize anthocyanidin and other flavonoids.The cDNA encoding F3H was cloned through RT-PCR and RACE using cDNA template prepared from young leaves of a mulberry (Morus multicaulis) variety named Yu 711.The obtained gene was designated as MmF3H (GenBank accession number KU301748).This gene has an open reading frame (ORF) of 1 095 bp,which encodes a protein of 365 amino acid with a predicted molecular weight of 40.15 kD and an isoelectric point of 4.93.Amino acids encoded by this gene share a sequence similarity of 98％ with F3H of Morus notabilis,and of 79％ to 82％ with other 5 plant species,indicating high conservatism of F3H-coded amino acid sequences.Phylogenetic tree revealed that F3H from Morus multicaulis and Morus notabilis clustered together,implying that they had the closest genetic relationship.Remarkable differences among expression levels of F3H gene in 35 mulberry germplasm resources were observed through real-time quantitative PCR analysis.Its highest and lowest relative expression level was 0.784 5 and 0.012 1 respectively.Measurement by spectrophotometry also revealed great differences among content of total flavonoids and content-of total anthocyanidins in the 35 mulberry germplasm resources.Moreover,the difference of total flavonoids has certain correlation with expressional difference of MmF3H gene,suggesting that the product from MmF3H catalyzed reaction belongs to the upstream product in flavonoid biosynthetic pathway.