Journal of Biotechnology 97 (2002) 213–221

Abstract
It has been suggested that the rol genes of Agrobacterium rhizogenes could play an essential role in the activationof secondary metabolite production in plant transformed cultures. This study investigated whether the content ofanthraquinone phytoalexins was changed in callus cultures of Rubia cordifolia transgenic for the 35S-rolB and 35S-rolC genes in comparison with a non-transformed callus culture. The anthraquinone content was shown to besignificantly increased in transgenic cultures, thus providing further evidence that the rol-gene transformation can be used for the activation of secondary metabolism in plant cells. Methyl jasmonate and salicylic acid strongly increasedanthraquinone accumulation in both transgenic and non-transgenic R. cordifolia calluses, whereas ethephon did not. A treatment of the cultures by cantharidin, the protein phosphatase 2A inhibitor, resulted in massive induction ofanthraquinone accumulation in the transgenic cultures only. We suggest the involvement of a cantharidin-sensitiveprotein phosphorylation mechanism in anthraquinone biosynthesis in transgenic cultures.