BIOLOGICAL FACTORS AFFECTING TRANSIENT TRANSFORMATION IN EMBRYOGENIC SUSPENSION-CULTURES OF PICEA-ABIES

Embryogenic suspension cultures of Picea abies were bombarded with gen e constructs containing the uidA reporter gene driven by different pro moters to study how biological factors affect transient gene expressio n. A number of cell-lines were tested of which A66 and B17 were chosen for further specific analysis. These cell-lines were representative o f a type A and type B embryogenic suspension culture, respectively, wi th this classification being based upon embryo morphology and regenera tion capacity. In both cell-lines intermediate sized cells in the embr yonic region of the somatic embryos appeared uidA positive, irrespecti ve of which promoter was used. However, there were significant differe nces in transient gene expression depending on cell-line, promoters an d time of bombardment after subculture. All promoters (35S, 2 x 35S, A ct1-D, and Dc8) showed significantly higher expression in cell-line B1 7 than A66, despite the higher growth rate of A66. The variation in tr ansient gene expression with time after subculture was characteristic for promoter and cell-line, but it appeared not to relate to changes i n mitotic index. Therefore, biological factors other than embryo morph ology, growth rate or mitotic index account for the differences in tra nsient expression.