MORPHOLOGICAL-CHANGES IN TRANSGENIC POPULUS CARRYING THE ROLC GENE FROM AGROBACTERIUM-RHIZOGENES

We have employed the reporter gene rolC gene from Agrobacterium rhizog enes as a morphologically detectable marker system for investigating g rowth alterations in Populus. A hybrid aspen (P. tremula L. x P. tremu loides MICHX.) clone, Esch5, was transformed using different chimeric gene constructs including the rolC gene to study its effect on morphol ogical and physiologically-conditioned parameters. Mainly, transgenic aspen carrying the rolC gene under control of the cauliflower-mosaic-v irus 35S-promoter and the light inducible rbcS promoter from potato we re compared with controls. Other gene constructs, in which rolC expres sion is prevented by insertion of the transposable element Ac from mai ze were also included. Differences in growth parameters (e.g. plant he ight, stem diameter, number of leaves), and growth arrest and terminal bud formation were observed between the control and the 35S-rolC tran sgenic aspens. Evaluation of onset of dormancy in the autumn and flush ing in the next spring revealed differences between untransformed cont rols and, in particular, the 35S-rolC transgenic plants. These tree-sp ecific morphological and developmental characteristics are discussed i n the Light of the transferred foreign genes in aspen-Populus, a woody plant model system.