Piriformospora indica elicitation of withaferin A biosynthesis and biomass accumulation in cell suspension cultures of Withania somnifera

Withania somnifera, is an important medicinal plant in India, also known as Ashwagandha, that contains the bioactive compounds- withanolides and withaferin A. The endophytic fungus Piriformospora indica has been shown to be an elicitor stimulating plant growth and metabolism. Different concentrations of cell homogenate, culture filtrate and individual culture discs of P. indica were added to cell suspension and callus cultures of W. somnifera at different time intervals (10, 15, 20, 25 and 5, 10, 15, 20 days respectively) to observe the effect on cell biomass and withaferin A production. Of all the concentrations of P. indica used to study the effect on withaferin A production in cell suspension cultures, the maximum enhancement was achieved with 3 % cell homogenate (2.04 times), followed by 3 % culture filtrate (1.78 times) and culture disc (1.46 times). Quantitative PCR analysis showed an effect of P. indica elicitation on the regulatory genes of MVA, MEP and withanolides biosynthetic pathways, viz. hmgr, fpps, ss, se, cas, dxs and dxr in callus and cell suspension cultures. The highest gene expression of 11.2, 8.7 and 6.9 times was observed with hmgr among all the expressed genes in cell suspension and callus cultures with 3 % cell homogenate, 3 % culture filtrate and disc respectively, in comparison with the controls.