An early gene of the flavonoid pathway, flavanone 3-hydroxylase, exhibits a positive relationship with the concentration of
catechins in tea (Camellia sinensis)
Kashmir Singh (1, 2), Arti Rani (1), Sanjay Kumar (1, 3), Payal Sood (1), Monika Mahajan (1), Sudesh K. Yadav (1), Bikram Singh (1, 4) and Paramvir S. Ahuja (1)
1. Biotechnology Division, Institute of Himalayan Bioresource Technology, P.O. Box No. 6, Palampur-176061, India / 2. Present address: Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University,
Miedzychodzka 5, 60 371, Poznan, Poland / 3. Corresponding author () / 4. Natural Plant Products Division, IHBT Palampur, India / Received October 20, 2007; accepted April 14, 2008; published online July 1, 2008
Summary
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 µM 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.
