cDNA cloning and expression analysis of the chalcone synthase gene (CHS) from Polygonum minus

Flavonoids are secondary metabolites that are present at high levels in the Polugonum minus. In recent years, flavonoids have attracted the interest of researchers because of their antioxidant properties .Flavonoids are synthesised via the condensation of 4 coumaryl-CoA and 3 malonyl-CoA by the action of Chalcone synthase. A cDNA encoding a chalcone synthase was isolated from the leaves of Polygonum minus by rapid amplification of cDNA ends (RACE) and designated pmCHS (GenBank accession no. JQ801338). The full-length cDNA of P. minus pmCHS was 1472 bp with a 1179 bp open reading frame (ORF) that corresponded to a predicted protein of 392 amino acid deduced protein. In silico analysis showed that the calculated molecular weight and theoretical isoelectric point (pI) of pmCHS were 43.1 kDa and 5.78, respectively. Several important motifs, such as the product binding site, active site and dimer interface, were also successfully identified from the deduced amino acid sequence. Multiple sequence alignment indicated that the pmCHS sequence was highly conserved and shared high sequence identity (>90%) with chalcone synthases from other plants. Gene expression analysis via qRT-PCR showed that pmCHS was most highly expressed in the roots, showing a 10-fold increase compared to leaves and a 15-fold increase compared to stems . The specific mechanism underlying the high expression of pmCHS in the roots requires further investigation.