Fraunhofer Gesellschaft 1 article published in JoVE Bioengineering Characterization of Complex Systems Using the Design of Experiments Approach: Transient Protein Expression in Tobacco as a Case Study Johannes Felix Buyel1, Rainer Fischer1,2 1Institute for Molecular Biotechnology, RWTH Aachen University, 2Institute for Molecular Biology and Applied Ecology, Fraunhofer Gesellschaft We describe a design of experiments approach that can be used to determine and model the influence of transgene regulatory elements, plant growth and development parameters, and incubation conditions on the transient expression of monoclonal antibodies and reporter proteins in plants.