ACTIVATION TAGGING IN POPULUS

¹ Department of Forest Science,Oregon State University, Corvallis, OR 97331-5752, USA

² Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada

Taking advantage of the efficient transformation system in poplar we were able to use activation tagging to generate dominant mutations by overexpressing genes near the insertion sites of a 35S enhancer tetramer. We recovered nearly 700 independent tag events. The rate of mutant recovery after screening in tissue culture, greenhouse and 2 growing seasons in the field is 3.4%. Mutations affect leaf morphology, stem elongation, crown architecture and apical dominance. Using this population we cloned the first activation tagged gene in a tree, encoding the major catabolic enzyme in plants GA 2-oxidase and have characterized the phenotypic and metabolic consequences of the ectopic expression of the gene. The implications of this mutant and insertion mutagenesis approaches to understanding tree development will be discussed.