Biological Factors Affecting Transient Transformation in Embryogenic Suspension Cultures of Picea abies

Abstract

Summary Embryogenic suspension cultures of Picea abies were bombarded with gene constructs containing the uid A reporter gene driven by different promoters to study how biological factors affect transient gene expression. A number of cell-lines were tested of which A66 and B17 were chosen for further specific analysis. These cell-lines were representative of a type A and type B embryogenic suspension culture, respectively, with this classification being based upon embryo morphology and regeneration capacity. In both cell-lines intermediate sized cells in the embryonic region of the somatic embryos appeared uid A positive, irrespective of which promoter was used. However, there were significant differences in transient gene expression depending on cell-line, promoters and time of bombardment after subculture. All promoters (35S, 2 x 35S, Act1 -D, and Dc8 ) showed significantly higher expression in cell-line B 17 than A66, despite the higher growth rate of A66. The variation in transient gene expression with time after subculture was characteristic for promoter and cell-line, but it appeared not to relate to changes in mitotic index. Therefore, biological factors other than embryo morphology, growth rate or mitotic index account for the differences in transient expression.