Patent ID: 6852846

Claim:
A method of expressing a foreign gene product in a plant cell, the method comprising: providing a chromosomally integrated transgene in a plant cell, wherein the transgene comprises a replicon having a plus sense RNA viral replication origin and at least one foreign gene capable of expression in a plant or a plant cell, wherein said replicon is transcribed from a promoter, and wherein said replicon is dependent for replication on a helper virus; providing the helper virus, wherein the helper virus comprises a plus sense RNA viral replicase; transcribing the transgene using a host RNA polymerase II to form recombinant mRNAs comprising the replicon; replicating the recombinant mRNAs with the plus sense RNA viral replicase, thereby producing additional replicon components; and producing subgenomic mRNA from the additional replicon components, thereby expressing the foreign gene product in the plant cell.