Deciphering Biosynthetic Machinery of Podophyllotoxin Anticancer Metabolite of Podophyllum hexandrum Royle

Abstract

Podophyllum hexandrum Royle (P. hexandrum) is known for its vast medicinal properties particularly, anticancer. It contains higher amount of podophyllotoxin (4.3%), compared to P. peltatum (0.025%) and other plant species, as a result has been used worldwide in the preparation of various drugs including, anticancer, antimalarial, antiviral, antioxidant, antifungal, and so on. Currently, Etoposide (VP-16-213), VUMON® (Teniposide; VM-26), Etopophos®, Pod-Ben- 25, Condofil, Verrusol and Warticon are available in the market. Podophyllotoxin is commercially isolated from roots and rhizomes of Podophyllum species. However, limited availability and finite amount of raw material, highly complex synthesis, and low cell culture yields of podophyllotoxin (0.3%), necessitate alternate sources/production routes for meeting increasing demands of podophyllotoxin. Further increase in podophyllotoxin content can only be achieved through genetic interventions in podophyllotoxin biosynthetic pathway. However, the knowledge on podophyllotoxin biosynthetic and regulatory machinery (pathway genes, transcription factors, ABC transporters and miRNAs) vis-à-vis podophyllotoxin content is lacking. Therefore, the current study was focused on i) identification of pathway components/genes contributing to podophyllotoxin biosynthesis ii) determination of crucial regulatory components such as transcription factors, ABC transporters and miRNAs implicated in podophyllotoxin biosynthesis in Podophyllum hexandrum. newlineThe present work utilized the available transcriptomes resources of Podophyllum hexandrum to identify, characterize and validate the molecular components associated with the podophyllotoxin biosynthesis. The work led to the identification of candidate pathway genes COMT, CM, PD, ADT, C4H, C3H, CCR, CAD and SRD that showed increase in transcript abundance up to 1.4 to 23.05 folds, respectively vis-à-vis podophyllotoxin content in roots (1.37%) and rhizomes (3.05%) of P. hexandrum. Comparative transcriptome analysis of Podophyllum species