Elastin-like polypeptide fusions enhance the accumulation of recombinant proteins in tobacco leaves

The production of recombinant proteins in plants is an active area of research and many different high-value proteins have now been produced in plants. Tobacco leaves have many advantages for recombinant protein production particularly since they allow field production without seeds, flowers or pollen and therefore provide for contained production. Despite these biosafety advantages recombinant protein accumulation in leaves still needs to be improved. Elastin-like polypeptides are repeats of the amino acids "VPGXG" that undergo a temperature dependant phase transition and have utility in the purification of recombinant proteins but can also enhance the accumulation of recombinant proteins they are fused to. We have used a 11.3 kDa elastin-like polypeptide as a fusion partner for three different target proteins, human interleukin-10, murine interleukin-4 and the native major ampullate spidroin protein 2 gene from the spider Nephila clavipes. In both transient analyses and stable transformants the concentrations of the fusion proteins were at least an order of magnitude higher for all of the fusion proteins when compared to the target protein alone. Therefore, fusions with a small ELP tag can be used to significantly enhance the accumulation of a range of different recombinant proteins in plant leaves.