3.4.1. Metabolic engineering
For industrial scale and sustainable production of taxol and related taxanes, numerous studies have focused on the synthesis of precursors involved in the synthesis of taxol from plant cell cultures. Cloning of taxadiene synthase (TXS ) and 10-deacetylbaccatin III-10-O-acetyltransferase (DBAT ) genes is an important biotechnological approach to increase the production of two precursor taxoids: 10-deactylbaccatin III (DB) and bacctin III (BC) to synthesize taxol. Taxus mairei cells transformed with TXS andDBAT genes with the addition of an elicitor MeJA produces 2.5 times higher taxoids than non-MeJA treated control cells (Ho et al., 2005). Similarly, transformed roots of T. baccata shows 265% greater taxane production after MeJA elicitor treatment, with over-expression of the TXS gene also being identified as an important contributory factor (Wilson and Roberts, 2014; Expósito et al., 2009; Engels et al., 2008). Exogenous feeding of taxol is another phenomenon to produce taxol and related taxane products in Taxus baccatasuspension cultures. DNA laddering analysis reveals that the addition of taxol caused a considerable increase in taxadiene synthase activity (Expósito et al., 2009).