ENHANCEMENT OF SHORT-TERM AND MEDIUM-TERM EXPRESSION OF TRANSGENES INEMBRYOGENIC SUSPENSIONS OF PICEA-ABIES (L) KARST

Biolistic transfer and subsequent reporter gene expression was enhance d 3-20-fold in embryogenic suspension cultures of Picea abies by treat ment with osmotica before and after bombardment. Myoinositol was more effective than mannitol+sorbitol and about as effective as sucrose in enhancing expression id after bombardment. For both myoinositol and su crose the optimal concentration was 0.25 M. Abscisic acid interacted w ith myoinositol to give a further enhancement. Maintaining the cells o n 0.25 M myoinositol after bombardment enhanced the expression measure d 10 d later. These results provide evidence for a metabolic component of the mechanism of osmotic enhancement in addition to an effect depe nding on partial plasmolysis at the time of bombardment. Expression dr iven by the polyubiquitin promoter 10 d after bombardment was more tha n twice that driven by an enhanced 35S, and 20 times that driven by a simple 355 promoter. Experiments using plasmids with and without scaff old attachment regions indicated that a greater proportion of the cell s that expressed the reporter gene at 6 d compared with 1 d after bomb ardment had been integratively transformed.