Improved effects of polyethylene glycol on the growth, antioxidative enzymes activity and taxanes production in a Taxus baccata L. callus culture

Abstract

Application of abiotic stress-inducing elicitors is one of the effective strategies in order to increase the production of secondary metabolites in plant tissues. Here, the effect of in vitro polyethylene glycol (PEG)-induced drought stress on morphological and biochemical changes as well as the production of paclitaxel and 10-deacetyl baccatin III in a Taxus baccata callus culture was investigated. The results showed that increased PEG concentration in the culture medium enhanced the levels of H2O2 and the membrane lipid peroxidation in the calli. The activity of catalase and guaiacol peroxidase as antioxidant responses were increased significantly in all PEG concentrations. At 6% of PEG concentration, the levels of fresh weight (FW) and dry weight (DW) in the calli were declined significantly by dropping in the amount of water content in the calli and rising the level of oxidative stress, and the morphological changes occurred following the increased browning index of the calli. However, the PEG at low to moderate concentrations reduced the accumulation and oxidation of phenolic compounds in the calli through the absorption of phenolic compounds and the reduction in the activity of the polyphenol oxidase. As a result, improved growth and viability of the calli resulted in the enhanced levels of FW and DW at the concentrations of 1% up to 3% (w/v) PEG. The highest contents of 10-deacetyl baccatin III and taxol were obtained at concentrations of 2% and 3% PEG, respectively. The concentration of 3% PEG increased the production of taxol by 2.5 times more than the control. In conclusion, PEG can be proposed as an effective elicitor in the production of taxanes in the Taxus cell and tissue cultures.