Abstract: A method for the expression of multiple proteins in a transgenic plant comprising inserting into the genome of the plant a gene construct comprising a 5'-region which includes a promoter which is capable of initiating transcription of a structural gene under the control thereof, a protein encoding sequence coding for more than one protein and a 3'-terminator region which includes a polyadenylation signal, each of the protein encoding sequences being separated from an adjacent protein encoding sequence by a DNA sequence which on translation provides a cleavage site whereby the expressed polyprotein is post-translationally processed into the component protein molecules. The DNA sequence which encodes the post-translation cleavage site may be derived from a virus, particularly a picornavirus. In a preferred embodiment the DNA sequence providing the cleavage site encodes the amino acid sequence NFDLLKLAGDVESNPGPFF.