Dedifferentiated Taxus media cell cultures presenting the same genetic characteristics as the parent culture were established from transformed roots. Two transformed cell lines were studied: Rol C, carrying the T-DNA of A. rhizogenes 9,402 and TXS, carrying both the T-DNA of A. rhizogenes and the txs transgene of T. baccata under the control of the 35S CaMV promoter. In the second part of a previously optimized two-stage system, the transformed cell lines were cultured in a production medium supplemented with the elicitor methyl jasmonate. Taxane production in the transformed cultures was compared with an untransformed T. media cell line cultured in the same conditions. The highest taxane production was observed in the TXS cell line when cultured in the optimized production medium with methyl jasmonate, being 265% greater than in the untransformed control and 170% greater than in the Rol C cell line. However, txs expression and the activity of the enzyme taxadiene synthase in the TXS cells were lower than in the line carrying only the rol genes (Rol C). It is also noteworthy that the taxane production as well as the txs gene expression and TXS activity in all the cell lines, both transformed and untransformed, were clearly dependent on the elicitor action. (C) 2010 American Institute of Chemical Engineers Biotechnol. Prog., 26: 1145-1153, 2010