Expression of avian reovirus minor capsid protein in plants

The minor coat protein of the avian reovirus (ARV), sigma C, encoded by the Si genome segment, is one of the major candidates for the development of a subunit vaccine against ARV infection. To develop a plant-based vaccine to immunize poultry against ARV infection, we constructed 4 plant nuclear expression vectors with or without codon modification of the 51 gene, and their expression was driven by a CaMV 35S promoter or rice actin1 promoter. In addition, the expressed sigma C proteins were targeted subcellularly to cytosol or chloroplasts, respectively. Agrobacterium containing the S1 expression constructs was used to transform tobacco leaf disks, and transformants were selected with kanamycin (100 mu g/ml). The integration of the S1 transgene into the tobacco chromosome was confirmed by PCR and Southern blot analysis. Western blot analysis with antiserum against sigma C was performed to determine the expression of sigma C protein in transgenic tobacco plants. The highest expression levels of sigma C protein in the cellular extracts of selected p35S1, pActS1 and p35UmS1 transgenic lines were 0.013%, 0.021% and 0.0013% of the total soluble protein, respectively, but the protein was barely detectable in p35TmS1 transgenic lines. However, the level of sigma C protein expression was not associated with the level of corresponding RNA transcripts in selected transgenic lines. Taken together, the results suggest that the major limiting factor for the expression of sigma C protein in plants might be at the post-transcriptional level. (C) 2011 Elsevier B.V. All rights reserved.