An approach to the conservation of the endangered yew (Taxus baccata L.) by optimizing callus culture for taxol production

  Taxus baccata is one of the native forest species in Iran. It is one of the most important sources of taxol, an anti-cancer compound. This plant is an endangered species due to its low growth and regeneration and also over-harvesting. Taxol production by tissue culture technique can protect this plant from the danger of extinction. In this study, the improvement of the growth of callus and taxol production in Taxus baccata were assessed using chemical absorbents and antioxidant compounds. Material and Activated charcoal (1 g/l), Polyvinylpyrrolidone (PVP; 250 mg/l) and an antioxidant compound (0.2 g/l glutamine, 0.05 g/l ascorbic acid and 0.05 g/l citric acid) were used for treating in a callus growth medium. Four grams of 60 day-old calli were transferred to a callus growth medium containing each of the treatments, where the untreated culture medium was considered as the control group. After 21 days, the amount of callus browning, wet weight, dry weight and viability as growth and morphological factors and also hydrogen peroxide (H2O2), malondialdehyde, total phenol, polyphenol oxidase activity and taxol amount as phytochemical factors were studied and evaluated. The results of morphological and phytochemical changes of calli under treatments showed that the antioxidant compound reduced the H2O2 and lipid peroxidation amount and with the reduction of oxidative stress, browning of tissues decreased. Also, under this treatment, with decreasing total phenol and activity of phenoloxidase, the amount of phenol oxidation decreased significantly. So, cell viability and wet and dry weight were increased and the amount of tissue browning was decreased. By absorbing the phenolic compound, activated charcoal and PVP decreased the polyphenol oxidase activity. The decrease in the polyphenol oxidase activity increased cell viability and prevented tissue browning. Under these treatments, no significant changes in H2O2 and MDA content, and wet and dry weight was observed. No changes were observed in the callus growth, which may be due to the absorption of hormones and vitamins along with the absorption of toxic compounds from the medium. All treatments were effective in decreasing the amount of tissue browning and increasing the viability of calli, but antioxidant compound treatment was the most effective in improving growth and increasing wet and dry weight with increasing taxol. Therefore, it is suggested as the best treatment for optimizing the callus culture of yew.