Isolation and functional characterization of a cDNA coding a hydroxycinnamoyltransferase involved in phenylpropanoid biosynthesis in Cynara cardunculus L

A gene sequence encoding a hydroxycinnamoyltransferase (HCT) involved in the synthesis of CGA, was identified. Isolation of the gene sequence was achieved by using a PCR strategy with degenerated primers targeted to conserved regions of orthologous HCT sequences available. We have isolated a 717 bp cDNA which shares 84% aminoacid identity and 92% similarity with a tobacco gene responsible for the biosynthesis of CGA from p-coumaroyl-CoA and quinic acid. In silico studies revealed the globe artichoke HCT sequence clustering with one of the main acyltransferase groups (i.e. anthranilate N-hydroxycinnamoyl/benzoyltransferase). Heterologous expression of the full length HCT (GenBank accession DQ104740) cDNA in E. coli demonstrated that the recombinant enzyme efficiently synthesizes both chlorogenic acid and p-coumaroyl quinate from quinic acid and caffeoyl-CoA or p-coumaroyl-CoA, respectively, confirming its identity as a hydroxycinnamoyl-CoA: quinate HCT. Variable levels of HCT expression were shown among wild and cultivated forms of C. cardunculus subspecies. The level of expression was correlated with CGA content.The data support the predicted involvement of the Cynara cardunculus HCT in the biosynthesis of CGA before and/or after the hydroxylation step of hydroxycinnamoyl esters.Cynara cardunculus L. is a perennial member of the Asteraceae family and has been sub-classified into three taxa: globe artichoke (var. scolymus L.), cultivated cardoon (var. altilis DC), and wild cardoon [var. sylvestris (Lamk) Fiori]. Molecular, cytogenetic and isozyme evidence suggests that wild cardoon is the ancestor of both cultivated forms [1-3].Globe artichoke plays an important role in human nutrition, mainly in Mediterranean diet: immature inflorescences (capitula), commonly referred to as 'heads' or 'buds', are consumed as a fresh, canned or frozen vegetable, while more recently, demand has been driven by its reputation as health food.The species has interesting applications in ph