Transformation as a Tool for Genetic Analysis in Populus

We summarize the outlook for using transformation as a genetic tool in Populus. Transformation approaches avoid the major obstacle to performing genetics experiments in trees – namely long generation cycles and the difficulty of inbreeding to reveal loss of function alleles. Dominant transgenic alleles allow modifications in gene function to be readily observed in primary transformants. Although transformation has been mainly used for reverse genetics (where the gene sequence of interest is known), transgenic mutagenesis approaches such as activation tagging and gene/enhancer traps have also been shown to enable forward genetics (where the phenotype, not the gene, is known). We outline challenges and needs for more efficient use of transformation tools. These include expansion of the transformation toolbox (e.g., promoters, vectors, targeting), and improved ability to conduct field trials to study gene function in native and plantation environments (in spite of regulatory obstacles). Because of the power of transformation, it will remain a major genetic research tool for dissection of gene function in Populus for many years to come. It is the key biological attribute that makes poplar the most powerful model organism for genetic analysis of woody plant growth, adaptation, and development.