title: Cloning and characterization of a flavanone 3-hydroxylase gene from Saussurea medusa.
abstract: Flavanone 3-hydroxylase (F3H) is a key enzyme in the flavonoid biosynthetic pathway, providing a branching point for the biosynthesis of different flavonoids, including the formation of 3-deoxy and 3-hydroxy flavonoids found in the silks of maize. Here, we report the cloning and characterization of a F3H gene (Smf3h) from a cDNA library derived from a red line callus of Saussurea medusa, a traditional Chinese medicinal plant. The cDNA contains a 1032 bp open reading frame (ORF) encoding a protein of 343 amino acid residues, a 149 bp long 5'untranslated regions (UTR) and a 163 bp long 3'UTR containing three putative polyadenylation signals (AATAAA) and an ATTTA element. The secondary structure of the mRNA predicted by MFOLD is very complex, suggesting a role in a post-transcriptional mechanism of regulation of Smf3h. The genomic structure of Smf3h includes four exons and three introns within the coding region, with all the splice donor/acceptor site sequences in accordance with the "GU-AG" consensus rule. The deduced SmF3H protein is 343 amino acid residues in length and has 40% and 39% identity and 60% and 58% similarity to the F3H of Arabidopsis and rice, respectively. Strikingly, the identity of SmF3H is higher to the H6H (hyoscyamine 3beta-hydroxylase, 45%) from Atropa belladonna. However, the analysis of the active center and the predicted protein secondary structure are more related to F3H than H6H. Together, our studies provide the first identification of a S. medusa flavonoid gene and its similarities to metabolic enzymes from other plants.
authors.affiliation: Institute of Botany, Chinese Academy of Sciences, 20# Nanxincun, Xiangshan, Haidian district, Beijing, P.R. China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Jin
authors.forename: Erich
authors.initials: E
authors.lastname: Grotewold
authors.forename: Wenquan
authors.initials: W
authors.lastname: Qu
authors.forename: Ghunxiang
authors.initials: G
authors.lastname: Fu
authors.forename: Dexiu
authors.initials: D
authors.lastname: Zhao
mesh_terms: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005091:Exons; D020224:Expressed Sequence Tags; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D006639:Histidine / Q000737:chemistry; D007438:Introns; D008516:Medicine, Chinese Traditional; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D030441:Saussurea / Q000201:enzymology* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D018076:DNA, Complementary; D012333:RNA, Messenger; D006639:Histidine; D012313:RNA; D004247:DNA; D006899:Mixed Function Oxygenases; C048797:flavanone 3-dioxygenase