Plant-based expression systems for the production of recombinant proteins have been the subject of numerous studies in recent years. It is now evident that plant-based systems offer a number of major advantages over conventional fermentation and cell-culture systems, such as the exclusion of mammalian pathogens or bacterial endotoxins, enhanced economics of scale-up, and a lower cost of products. The assembly of complex multimeric proteins such as secretory IgAs, which are difficult to manufacture in other systems, has also been demonstrated in plants. However, even within plant systems, there are a variety of combinations and mechanisms for the expression of a specific protein. For instance, the choice of host species may be influenced by biochemistry, extraction, post-extraction processing or regulatory characteristics. Similarly, within a plant, the deposition of the protein in particular tissues, organs, or even subcellular compartments can have a significant impact on the efficiency and economics of production. Although it has been demonstrated that recombinant proteins may be expressed in vegetative cells such as leaves, tubers, and roots, there are unique advantages to depositing recombinant proteins in seeds. Plant seed oil or oleosomes consume the neutral lipid reserve found in seeds. In several oil seeds, these organelles may account for half of the overall cell volume. The most prevalent proteins in oil seeds are oleosins. By flotation-centrifugation of aqueous seed extracts, oil bodies and their associated oleosins can be extracted. This straightforward partitioning procedure resulted in a remarkable enrichment of oleosins in the oil body fraction.