Turnip Mosaic Virus as a vector for plant gene expression
Zahra Agharbaoui, Chantal beauchemin, Véronique Bougie et Jean-François Laliberté
It is important to develop strategies for the synthesis of biopharmaceutical products that are more efficient and economical. At present, recombinant proteins are generally made in mammalian, insect, fungus and prokaryotic cells. Plants also offer advantages for the production of biopharmaceutical proteins. Transgenic plants do not always synthesise enough protein of interest. The use of viral vector has attracted interest because they can rapidly produce high yields of proteins. In this study, we have used Turnip mosaic virus (TuMV) for the development of such a vector. TuMV is a positive sense RNA virus of approximately 10 kb in length. It codes for a single polyprotein that is processed into ten mature proteins by viral proteases. Important features of TuMV as a vector are: 1) the protein of interest is part of the polyprotein and is synthesised at the same level as the capsid protein. 2) It is possible to produce more than one protein of interest with the same construct. Two insertion sites were tested. The reporter gene, gfp or uidA, were inserted between P1/HC-Pro or Pol/CP genes, either individually or in combination in the infectious clone. After particle bombardment of Brassica perviridis, we observed symptoms similar to those caused by TuMV. Western blot analysis, fluorescent microscopy and enzymatic assays showed that GFP and GUS were produced to high levels. We also demonstrate that it was feasible to introduce the two genes in the same construct and obtain the expression of both. In conclusion, our vector offers the possibility of easily producing proteins of medical interest such as antibodies in high yields. This work is supported by grants from NSERC, fonds FCAR and Medicago Inc.