© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1203 Biotechnol. J. 2013, 8, 1203–1212 DOI 10.1002/biot.201300068 www.biotechnology-journal.com 1 Introduction Seeds provide a useful and versatile platform for the pro- duction of recombinant proteins because they are physi- ologically and morphologically adapted for protein stor- age. Desiccated seeds offer a stable and protease-free environment in which high concentrations of protein (up to 36.5% of total soluble protein, TSP [1]) can accumulate in a small tissue volume. Developing seeds also contain a rich mix of molecular chaperones and disulfide isomeras- es that facilitate protein folding [2, 3]. Although vegeta- tive tissues have a greater biomass, and a flowering cycle is unnecessary for the production of recombinant proteins [4, 5], these advantages are offset by the higher metabol- ic activity and greater water content of vegetative tissues, so that immediate processing, freezing or desiccation is necessary in order to avoid protein degradation [2, 6, 7]. Recombinant proteins expressed in vegetative tissues may also interfere with plant growth and development, whereas even toxic proteins can accumulate in seeds. Cereal crops (particularly maize, rice, barley, and wheat) are favored platforms for the production of recom- binant proteins because of their high yield and well- established agricultural infrastructure, allowing produc- tion to be scaled up and down rapidly in response to demand. The cereal endosperm is a suitable target for recombinant proteins because it is naturally adapted for protein accumulation and the number of transgene copies Research Article Efficient recovery of recombinant proteins from cereal endosperm is affected by interaction with endogenous storage proteins Jenny Peters 1 , Maite Sabalza 2 , Koreen Ramessar 2 , Paul Christou 2 , Teresa Capell 2 , Eva Stöger 1 and Elsa Arcalís 1 1 Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria 2 Department of Plant Production and Forestry Science, ETSEA, University of Lleida-Agrotecnio Center, Lleida, Spain Cereal seeds are versatile platforms for the production of recombinant proteins because they pro- vide a stable environment for protein accumulation. Endogenous seed storage proteins, however, include several prolamin-type polypeptides that aggregate and crosslink via intermolecular disul- fide bridges, which could potentially interact with multimeric recombinant proteins such as anti- bodies, which assemble in the same manner. We investigated this possibility by sequentially extracting a human antibody expressed in maize endosperm, followed by precipitation in vitro with zein. We provide evidence that a significant proportion of the antibody pool interacts with zein and therefore cannot be extracted using non-reducing buffers. Immunolocalization experiments demonstrated that antibodies targeted for secretion were instead retained within zein bodies because of such covalent interactions. Our findings suggest that the production of soluble recom- binant antibodies in maize could be enhanced by eliminating or minimizing interactions with endogenous storage proteins. Keywords: Maize endosperm · Molecular farming · Plantibodies · Protein trafficking Correspondence: Dr. Elsa Arcalis, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, Vienna, Austria E-mail: elsa.arcalis@boku.ac.at Current address: Maite Sabalza, Section of Cell and Development Biology, University of California, San Diego, La Jolla, CA, USA Koreen Ramessar, Molecular Targets Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, USA Paul Christou, Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain Abbreviations: ER, endoplasmic reticulum; HIV, human immunodeficiency virus; Ig, immunoglobulin; IL-10, interleukin 10; PSV, protein storage vacuole Received 27 MAY 2013 Revised 02 AUG 2013 Accepted 16 AUG 2013 Accepted article online 20 AUG 2013 Supporting information available online