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1.  The isolation and mapping of a novel hydroxycinnamoyltransferase in the globe artichoke chlorogenic acid pathway 
BMC Plant Biology  2009;9:30.
Background
The leaves of globe artichoke and cultivated cardoon (Cynara cardunculus L.) have significant pharmaceutical properties, which mainly result from their high content of polyphenolic compounds such as monocaffeoylquinic and dicaffeoylquinic acid (DCQ), and a range of flavonoid compounds.
Results
Hydroxycinnamoyl-CoA:quinate hydroxycinnamoyltransferase (HQT) encoding genes have been isolated from both globe artichoke and cultivated cardoon (GenBank accessions DQ915589 and DQ915590, respectively) using CODEHOP and PCR-RACE. A phylogenetic analysis revealed that their sequences belong to one of the major acyltransferase groups (anthranilate N-hydroxycinnamoyl/benzoyltransferase). The heterologous expression of globe artichoke HQT in E. coli showed that this enzyme can catalyze the esterification of quinic acid with caffeoyl-CoA or p-coumaroyl-CoA to generate, respectively, chlorogenic acid (CGA) and p-coumaroyl quinate. Real time PCR experiments demonstrated an increase in the expression level of HQT in UV-C treated leaves, and established a correlation between the synthesis of phenolic acids and protection against damage due to abiotic stress. The HQT gene, together with a gene encoding hydroxycinnamoyl-CoA:shikimate/quinate hydroxycinnamoyltransferase (HCT) previously isolated from globe artichoke, have been incorporated within the developing globe artichoke linkage maps.
Conclusion
A novel acyltransferase involved in the biosynthesis of CGA in globe artichoke has been isolated, characterized and mapped. This is a good basis for our effort to understand the genetic basis of phenylpropanoid (PP) biosynthesis in C. cardunculus.
doi:10.1186/1471-2229-9-30
PMCID: PMC2664813  PMID: 19292932
2.  Isolation and functional characterization of a cDNA coding a hydroxycinnamoyltransferase involved in phenylpropanoid biosynthesis in Cynara cardunculus L 
BMC Plant Biology  2007;7:14.
Background
Cynara cardunculus L. is an edible plant of pharmaceutical interest, in particular with respect to the polyphenolic content of its leaves. It includes three taxa: globe artichoke, cultivated cardoon, and wild cardoon. The dominating phenolics are the di-caffeoylquinic acids (such as cynarin), which are largely restricted to Cynara species, along with their precursor, chlorogenic acid (CGA). The scope of this study is to better understand CGA synthesis in this plant.
Results
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.
Conclusion
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.
doi:10.1186/1471-2229-7-14
PMCID: PMC1847684  PMID: 17374149

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