Dennis Mccabe

A Transient Assay for Heterologous Promoter Activity in Picea Glauca

One important aspect of the successful genetic engineering of trees is the proper and coordinated expression of introduced foreign genes in the tree. To date, few studies have focused on the controlled expression of foreign genes in forest trees. Using electrical discharge particle acceleration, the expression of several heterologous promoters were tested in Picea glauca (white spruce) embryos, seedlings and embryogenic callus. Promoters tested include: Arabidopsis and soybean ribulose-l,5-bisphosphate small subunit (rbcS) promoters, a maize phosphoenolpyruvate carboxylase (PEP) promoter, a soybean heat shock promoter, a maize alcohol dehydrogenase (ADH) promoter and a soybean auxin inducible promoter. All promoters were used to drive the β-glucuronidase marker gene and expression was determined both with and without the respective induction stimulus required for maximal promoter activity in the source plant. Furthermore, the induction stimuli were also tested to determine the effects of the stimuli on the expression of a cauliflower mosaic virus 35s promoter. While β-glucuronidase gene expression in white spruce embryos was detected from all promoters tested, inducible gene expression was observed only with the heat shock and ADH promoters. Expression in seedlings and embryogenic callus indicate that this method for transient assays allows testing not only of promoter activity but also of tissue and/or cell specific expression.