THE PATTERN OF CYTOKININ CONTENT IN TRANSGENIC AND WILD-TYPE TOBACCO SEEDLINGS AS AFFECTED BY HEAT-SHOCK

The pattern of the endogenous cytokinin content was monitored during the day in the shoots of transgenic tobacco plants (Nicotiana tabacum L.) containing a heat-inducible ipt gene responsible for isopentenyl-transferase synthesis. Heating transgenic plants at 40 degrees C for 1 h yielded an increase in endogenous cytokinins, as compared to the normal level in the plants kept at 24 degrees C for the whole period. However, this increase was not permanent, as after five hours following heat-shock treatment, there was essentially no difference in cytokinin content between heated and untreated plants. In the shoots of wild-type tobacco, heat shock activated the processes diminishing cytokinin concentration, which are the typical plant response to heat shock. When such a response also manifests itself in transgenic plants, it can cause a transient cytokinin accumulation after heat-shock treatment