title: An early gene of the flavonoid pathway, flavanone 3-hydroxylase, exhibits a positive relationship with the concentration of catechins in tea (Camellia sinensis).
abstract: Tea (Camellia sinensis (L.) O. Kuntze) leaves are a major source of flavonoids that mainly belong to the flavan 3-ols or catechins. Apart from being responsible for tea quality, these compounds have medicinal properties. Flavanone 3-hydroxylase (F3H) is an abundant enzyme in tea leaves that catalyzes the stereospecific hydroxylation of (2S)-naringenin to form (2R,3R)-dihydrokaempferol. We report a full-length cDNA sequence of F3H from tea (CsF3H Accession no. AY641730). CsF3H comprised 1365 bp with an open reading frame of 1107 nt (from 43 to 1149) encoding a polypeptide of 368 amino acids. Expression of CsF3H in an expression vector in Escherichia coli yielded a functional protein with a specific activity of 32 nmol min(-1) mg protein(-1). There was a positive correlation between the concentration of catechins and CsF3H expression in leaves of different developmental stages. CsF3H expression was down-regulated in response to drought, abscisic acid and gibberellic acid treatment, but up-regulated in response to wounding. The concentration of catechins paralleled the expression data. Exposure of tea shoots to 50-100 microM catechins led to down-regulation of CsF3H expression suggesting substrate mediated feedback regulation of the gene. The strong correlation between the concentration of catechins and CsF3H expression indicates a critical role of F3H in catechin biosynthesis.
authors.affiliation: Biotechnology Division, Institute of Himalayan Bioresource Technology, Palampur-176061, India.
authors.forename: Kashmir
authors.initials: K
authors.lastname: Singh
authors.forename: Arti
authors.initials: A
authors.lastname: Rani
authors.forename: Sanjay
authors.initials: S
authors.lastname: Kumar
authors.forename: Payal
authors.initials: P
authors.lastname: Sood
authors.forename: Monika
authors.initials: M
authors.lastname: Mahajan
authors.forename: Sudesh K
authors.initials: SK
authors.lastname: Yadav
authors.forename: Bikram
authors.initials: B
authors.lastname: Singh
authors.forename: Paramvir S
authors.initials: PS
authors.lastname: Ahuja
mesh_terms: D000367:Age Factors; D000595:Amino Acid Sequence; D028244:Camellia / Q000201:enzymology / Q000235:genetics*; D002392:Catechin / Q000096:biosynthesis*; D015536:Down-Regulation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D002392:Catechin; D006899:Mixed Function Oxygenases; C048797:flavanone 3-dioxygenase