Investigation of the Effects of the Basal Medium, Auxin and Antioxidants on the Induction and Maintenance of Callus and Taxol Production in Yew (Taxus baccata)

Abstract

Production of Taxol, the most promising chemotherapuetic drug, depends on Taxus spp.  cell culture. Since there are numerous difficulties in the in vitro cell culture of this recalcitrant genus, this study was conducted in order to establish an efficient protocol for callus induction and maintenance of it. Callus cultures from T. baccata young stems were established in B5 and MS media supplemented with different concentrations of 2,4-D and NAA. The effects of basal culture media, type and concentration of auxin were assessed on callus growth. The callus morphology (compactness and color) also was compared using non-parametric test (Mann–Whitney U test). The results showed that the best basal medium for callus induction and growth was in B5, and the highest callus growth in B5 medium obtained when NAA was supplied as auxin. Two mg/L NAA was the optimum auxin concentration among different applied levels of this hormone. The results also revealed that incubation of the calli in the dark conditions in the presence of 0.1 g/L of citric acid and ascorbic acid significantly reduced the phenolic secretion from calli, compared to those grown in light or those which were treated with 0.05 g/L of these antioxidants. Following experiments confirmed that stem of T. baccata was the best explant for callus induction and growth. In addition, the morphological study described various callus types and various colors formed during callus induction in the different conditions. The data related to this part confirmed that B5 medium and NAA provided the best tissue type (friable) and color (yellowish-green) of the calli. In the optimized medium, specific yield of Taxol was about 70 µg/g DW (Dry Weight). This amount of Taxol production is noticeable in Taxus spp. c alli, compared with available literature on the production of Taxol by T. baccata cells.