EFFECT OF CYTOKININ ON ALKALOID ACCUMULATION IN PERIWINKLE CALLUS-CULTURES TRANSFORMED WITH A LIGHT-INDUCIBLE IPT GENE

The effect of cytokinins on accumulation of indole alkaloids in periwi nkle callus cultures was investigated. Firstly, it was found that exog enously-applied cytokinin increased the ajmalicine and serpentine cont ent of untransformed callus culture obtained from cotyledons. Secondly , periwinkle cotyledons were transformed with the isopentenyl transfer ase (ipt) gene under the control of a light-inducible promoter and two transformed callus lines were used in order to investigate whether en dogenously-produced cytokinin could also increase the alkaloid product ion. We found that the ipt-transgenic tissues accumulated higher level s of isopentenyl transferase transcripts as well as zeatin riboside, e ven under non-inductive condition, but lower concentration of alkaloid s compared to that of untransformed tissues. A 28 kDa polypeptide whos e accumulation was previously found to be associated with alkaloid pro duction in a periwinkle cell suspension was also present in the non-tr ansformed tissue and its level was increased in parallel to the CK-enh anced alkaloid production. Neither light induction condition, nor exog enous cytokinin treatment led to the increase of the 28 kDa polypeptid e accumulation in the transformed tissues. All these data show that en dogenously-produced cytokinin does not mimic the effect of exogenously -applied cytokinin on the alkaloid production in periwinkle calli.