EXCISION OF THE MAIZE TRANSPOSABLE ELEMENT AC IN PERICLINAL CHIMERIC LEAVES OF 35S-AC-ROLC TRANSGENIC ASPEN POPULUS

The transposable clement Ac from maize, in combination with the phenot ypic selectable marker rolC, was employed in transformation experiment s of a hybrid aspen clone. A number of transgenic clones exhibited lig ht-green sectors on green leaves. In vitro regeneration from leaves sh owing a high number of light-green spots resulted in R2 plants, which also showed light-green sectored leaves. However, only one out of 385 regenerated plants obtained showed green leaves. Both PCR and northern analysis indicated Ac excision and restoration of rolC expression. In Southern blot analysis of this green plant additional bands were obse rved as compared to the original R1 plant. The occurrence of these ban ds and a suggested Ac excision in the non-green LI-epidermal layer lea ding to periclinal chimerism of this plant is discussed.