CHANGES OF BOTH POLYPEPTIDE PATTERN AND SENSITIVITY TO CYTOKININ FOLLOWING TRANSFORMATION OF PERIWINKLE TISSUES WITH THE ISOPENTENYL TRANSFERASE GENE

Two-dimensional gel electrophoresis was used to examine differences be tween the polypeptide patterns of an untransformed periwinkle callus l ine and a transformed line carrying the cytokinin biosynthesis gene is opentenyl transferase (ipt) under control of a light-inducible promote r. Both lines were cultured for three weeks on an auxin free medium wi th or without exogenously-added zeatin, in continuous light or in comp lete darkness. Firstly, it was found that exogenous cytokinin treatmen t increased the amount of at least 24 polypeptides and decreased the a mount of three polypeptides in the untransformed line. Secondly, a mar ked decrease in the number and the amount of the polypeptides was obse rved in the 2D-gels from the transgenic line. Traces of two cytokinin up-regulated polypeptides, the amounts of which have been previously f ound to be correlated with the accumulation of indole alkaloids in per iwinkle cells in vitro were present in this line. Lastly, exogenous cy tokinin treatment had very little effect on the polypeptide pattern of the transgenic line. These data show that endogenously-produced cytok inin does not mimic the effect of exogenously-applied cytokinin on the polypeptide accumulation in periwinkle callus cultures, and that the ipt-transgenic line has become insensitive to exogenous cytokinin trea tment.