Submitted to: Brewing Chemistry and Technology in the Americas
Publication Type: Trade Journal
Publication Acceptance Date: October 1, 2004
Publication Date: November 1, 2006
Citation: Dahleen, L.S. 2007. What is transformation, how has it been applied in barley research and what might the future hold?. In: Gales, P.W., editor. Brewing Chemistry and Technology in the Americas. St. Paul, MN: American Society of Brewing Chemists. p. 17. Technical Abstract: Transformation is the direct insertion and expression of individual genes into an organism like barley. The genes can come from any source, such as plants, animals, insects, bacteria, etc. A promoter is placed in front of the gene to control when and where the gene's product is made. Two primary methods are used to generate transgenic barley, particle bombardment and Agrobacterium co-cultivation. With particle bombardment, gold or tungsten particles are coated with DNA for the gene of interest (and the promoter) and physically propelled into barley cells. Agrobacterium co-cultivation methods use a bacterium that naturally infects plants and transfers its DNA to insert the gene of interest into barley cells. With both methods, a selectable marker gene also is inserted to allow separation of transformed and non-transformed cells. Two selectable markers commonly used for barley are the bar gene for herbicide resistance and the nptII gene for antibiotic resistance. Typical barley tissues used for transformation are immature embryos (mid-dough stage) and immature pollen grains. Both particle bombardment and Agrobacterium co-cultivation use tissue culture to select and multiply the transformed cells, and eventually regenerate green transgenic plants. In most research laboratories, 2-10% of the treated embryos or pollen grains will produce transgenic plants. Efforts are underway to increase this transformation efficiency. The future of transgenic barley depends on whether there is increased global public acceptance of genetically modified plants. If the current status holds, transformation will remain a valuable research tool to better understand gene functions and interactions in barley. If genetically modified barley becomes acceptable, transformation could have a large impact on strategies to improve barley quality for malting and brewing, human nutrition, and animal feed.