Cloning and expression analysis of chalcone synthase gene from Coleus forskohlii

Flavonoids are an important class of secondary metabolites that play various roles in plants such as mediating defense, floral pigmentation and plant-microbe interaction. Flavonoids are also known to possess antioxidant and antimicrobial activities. Coleus forskohlii (Willd.) Briq. (Lamiaceae) is an important medicinal herb with a diverse metabolic profile, including production of a flavonoid, genkwanin. However, components of the flavonoid pathway have not yet been studied in this plant. Chalcone synthase (CHS) catalyses the first committed step of flavonoid biosynthetic pathway. Full-length cDNA, showing homology with plant CHS gene was isolated from leaves of C. forskohlii and named CfCHS (GenBank accession no. KF643243). Theoretical translation of CfCHS nucleotide sequence shows that it encodes a protein of 391 amino acids with a molecular weight of 42.75 kDa and pI 6.57. Expression analysis of CfCHS in different tissues and elicitor treatments showed that methyl jasmonate (MeJA) strongly induced its expression. Total flavonoids content and antioxidant activity of C. forskohlii also got enhanced in response to MeJA, which correlated with increased CfCHS expression. Induction of CfCHS by MeJA suggest its involvement in production of flavonoids, providing protection from microbes during herbivory or mechanical wounding. Further, our in silico predictions and experimental data suggested that CfCHS may be posttranscriptionally regulated by miR34.