ENHANCEMENT OF THE ENDOGENOUS CYTOKININ CONCENTRATION IN POPLAR BY TRANSFORMATION WITH AGROBACTERIUM T-DNA GENE IPT

The agrobacterial isopentenyltransferase (ipt) gene, under the control of its native promoter, was transferred to poplar (Populus tremula x P. alba) by an Agrobacterium co-cultivation method. The ipt-transforme d stem explants developed calli that regenerated many buds in the abse nce of exogenous cytokinins. Microcuttings of the ipt transformants ex hibited frequently branching shoots with short internodes that were un able to root. In this material, the concentrations of zeatin, zeatin r iboside and isopentenyladenosine, determined by an indirect enzyme-lin ked immunosorbent assay (ELISA), were 4.8-, 17.1- and 14.6-fold higher , respectively, than in non-transformed shoots. Results are discussed with regard to cytokinin metabolism,