The present invention relates to the field of plant secondary metabolites, particularly terpenoid indole alkaloids. More particularly the present invention relates to the production of the anti-cancer metabolites vincristine and vinblastine. The invention provides novel polynucleotide sequences derived from Catharanthus roseus and the use of said polynucleotide sequences to stimulate the production of vinblastine and/or vincristine in plants of Catharanthus roseus and plant cell lines derived thereof. The invention further relates to recombinant plants, plant cells, tissue and organ cultures obtainable by the process of the invention.