Manipulating Plant Histone Genes to Improve Agrobacterium- and Direct DNA-mediated Plant Genetic Transformation

Introduction Agrobacterium-mediated plant genetic transformation has become a “core technology” for both plant basic research and for agricultural biotechnology applications. Compared to direct DNA uptake techniques, including PEG/electroporationmediated DNA uptake into protoplasts and particle bombardment, Agrobacterium-mediated transformation generally results in a lower integrated copy number of transgenes that show fewer rearrangements. This is important for regulatory purposes for which a complete characterization of foreign DNA is required for field-grown plants and for gene expression purposes: multiple copy transgene integration events have a higher propensity to “silence” than do low or single copy events. However, many plant species, or particular varieties/genotypes of these species, remain highly recalcitrant to Agrobacterium-mediated transformation. Improving transformation frequency remains an important aspect of applied Agrobacterium research. In addition, improving the “quality” of transgenic events (single-copy transgene integration, no vector “backbone” integration, and predictable and stable transgene expression) forms the basis of next-generation transformation technologies.