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CELL BIOLOGY AND SIGNAL TRANSDUCTION

The Intracellular Fate of a Recombinant Protein Is Tissue Dependent¹

Institute for Molecular Biotechnology, Biology VII, Aachen University, 52074 Aachen, Germany (G.D., S.M., E.A., R.F., E.S.); Department for Chemistry, Glycobiology Division, University of Natural Resources and Applied Life Sciences, 1190 Vienna, Austria (F.A.); Centro de Investigaciones Biologicas, Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain (P.G.-M.); and Department de Produccio Vegetal i Ciencia Forestal, Universitat de Lleida, E-25198 Lleida, Spain (P.C.)

Recombinant proteins directed to the secretory pathway in plants require a signal peptide for entry into the endoplasmic reticulum. In the absence of further targeting information, such proteins are generally secreted via the default pathway to the apoplast. This has been well documented in protoplasts and leaf tissue, but the trafficking of recombinant proteins in seeds and other storage tissues has rarely been investigated. We used Aspergillus niger phytase as a model glycoprotein to compare the intracellular fate of a recombinant protein in the leaves and seeds of rice (Oryza sativa). Using fluorescence and electron microscopy we showed that the recombinant protein was efficiently secreted from leaf cells as expected. In contrast, within endosperm cells it was retained in endoplasmic reticulum-derived prolamin bodies and protein storage vacuoles. Consistent with our immunolocalization data, the phytase produced in endosperm cells possessed oligomannose and vacuolar-type N-glycans [Man₃(Xyl)(Fuc)GlcNAc₂], whereas the phytase produced in leaves contained predominantly secretion-type N-glycans [GlcNAc₂Man₃(Xyl)(Fuc)GlcNAc₂]. The latter could not be detected in preparations of the endosperm-derived phytase. Our results show that the intracellular deposition and modification of a recombinant protein is tissue dependent.

² These authors contributed equally to the paper.

³ Present address: Center for Plant Cell Biology, Department of Botany and Plant Sciences, University of California, Riverside, CA 92521.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Eva Stoger (eva.stoger{at}molbiotech.rwth-aachen.de).

Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.106.076661.

^* Corresponding author; e-mail eva.stoger{at}molbiotech.rwth-aachen.de; fax 492418020145.

Received January 5, 2006; returned for revision April 5, 2006; accepted April 7, 2006.

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