Higher accumulation of F1-V fusion recombinant protein in plants after induction of protein body formation

Abstract

Improving foreign protein accumulation is crucial for enhancing the commercial success of plant-based production systems since product yields have a major influence on process economics. Cereal grain evolved to store large amounts of proteins in tightly organized aggregates. In maize, γ-Zein is the major storage protein synthesized by the rough endoplasmic reticulum (ER) and stored in specialized organelles called protein bodies (PB). Zera ® (γ-Zein ER-accumulating domain) is the N-terminal proline-rich domain of γ-zein that is sufficient to induce the assembly of PB formation. Fusion of the Zera® domain to proteins of interest results in assembly of dense PB-like, ER-derived organelles, containing high concentration of recombinant protein. Our main goal was to increase recombinant protein accumulation in plants in order to enhance the efficiency of orally-delivered plant-made vaccines. It is well known that oral vaccination requires substantially higher doses than parental formulations. As a part of a project to develop a plant-made plague vaccine, we expressed our model antigen, the Yersinia pestis F1-V antigen fusion protein, with and without a fused Zera® domain. We demonstrated that Zera®-F1-V protein accumulation was at least 3× higher than F1-V alone when expressed in three different host plant systems: Ncotiana benthamiana, Medicago sativa (alfalfa) and Nicotiana tabacum NT1 cells. We confirmed the feasibility of using Zera® technology to induce protein body formation in non-seed tissues. Zera® expression and accumulation did not affect plant development and growth. These results confirmed the potential exploitation of Zera® technology to substantially increase the accumulation of value-added proteins in plants. © 2009 Springer Science+Business Media B.V.