Protein expression systems

A gene expression construct for enhancing expression in a plant of a coding sequence for a protein heterologous to Cowpea Mosaic Virus (CPMV) comprising:

• at least one fragment of the RNA-2 genome segment of CPMV,
• wherein the fragment of the RNA-2 genome segment of CPMV consists essentially of:
• at least 100 contiguous nucleotides of SEQ ID NO:1 in an untranslated region (UTR) of the RNA-2 genome segment of CPMV as set forth in nucleotides 1 to 160 of SEQ ID NO:
• 10 for the 5′ UTR of the RNA-2 genome segment of CPMV or as set forth in nucleotides 533-716 of SEQ ID NO:
• 10 for the 3′ UTR of the RNA-2 genome segment of CPMV, and the fragment does not contain the target initiation site at positions 161-163 of SEQ ID NO:
• 1,
• and the coding sequence for the protein heterologous to CPMV,
• wherein the coding sequence is operably linked to a functional translation initiation site,
• and wherein when the gene expression construct is introduced into a plant, there is enhanced expression of the heterologous protein in comparison with a construct encoding the heterologous protein and having the target initiation site at positions 161-163 of SEQ ID NO:
• 1.