Molecular cloning and tissue-specific expression of two cDNAs encoding polyketide synthases from Hypericum perforatum

Area of Science:

• Plant molecular biology
• Biochemistry
• Pharmacognosy

Background:

• Hypericum perforatum (St. John's Wort) is a medicinal plant known for its bioactive compounds.
• Polyketide synthases (PKSs) are key enzymes in the biosynthesis of many plant secondary metabolites.
• Understanding PKS gene function is crucial for elucidating metabolic pathways.

Purpose of the Study:

• To isolate and characterize novel polyketide synthase (PKS) genes from Hypericum perforatum.
• To investigate the tissue-specific expression patterns of these newly identified PKS genes.
• To correlate PKS gene expression with the accumulation of specific phytochemicals.

Main Methods:

• cDNA isolation and sequencing to identify PKS genes (HpPKS1 and HpPKS2).
• Analysis of open reading frames (ORFs) and predicted amino acid sequences.
• Quantitative expression analysis across different plant tissues.
• Correlation analysis between gene expression and phytochemical concentrations (hyperforin, adhyperforin, hypericins, pseudohypericins).

Main Results:

• Two novel PKS cDNAs, HpPKS1 and HpPKS2, were successfully isolated and characterized.
• Both genes encode proteins with conserved catalytic residues typical of plant PKSs.
• HpPKS1 and HpPKS2 displayed distinct tissue-specific expression profiles within H. perforatum.
• HpPKS1 expression correlated with hyperforin/adhyperforin levels, while HpPKS2 correlated with hypericin/pseudohypericin levels.

Conclusions:

• HpPKS1 and HpPKS2 represent distinct PKS genes involved in the biosynthesis of different classes of secondary metabolites in H. perforatum.
• Tissue-specific expression suggests specialized roles in the production of hyperforins and hypericins.
• These findings provide insights into the genetic regulation of key phytochemical production in St. John's Wort.