Differential display mediated cloning of anthocyanidin reductase gene from tea (Camellia sinensis) and its relationship with the concentration of epicatechins

Abstract

Tea [Camellia sinensis (L.) O. Kuntze] leaves are a major source of epicatechin (EC) and its gallolyl derivatives epicatechin gallate, epigallocatechin and epigallocatechin gallate, collectively known as epicatechins (ECs). Epicatechins are important factors determining tea quality, and they also possess many medicinal properties. To gain further information about the regulation of the biosynthesis of ECs, we cloned the gene encoding anthocyanidin reductase from tea (CsANR) by first quantifying changes in the concentrations of ECs in response to drought, gibberellic acid (GA3), abscisic acid (ABA) and wounding treatments, followed by differential display of mRNAs and analysis of those bands exhibiting a change in expression paralleling the treatment-induced changes observed in the EC data. Analysis of 133 bands yielded a partial cDNA of CsANR that was later cloned to the full length by rapid amplification of the cDNA ends. The full-length CsANR (Accession No. AY641729) comprised 1233 bp with an ORF of 1014 bp (from 79 to 1092 bp) encoding a polypeptide of 337 amino acids. Expression of CsANR in an Escherichia coli expression vector yielded a functional protein that catalyzed the conversion of cyanidin to EC in the presence of NADPH. Analysis of ECs and gene expression in leaves at different developmental stages and across five tea clones exhibiting variable concentrations of ECs revealed a positive correlation between concentration of ECs and CsANR expression. Expression of CsANR was down-regulated in response to drought, ABA and GA3 treatments and up-regulated in response to wounding.