The present invention is directed to recombinant plant viral nucleic acids and to hosts infected thereby. The recombinant plant viral nucleic acids comprise a native plant viral subgenomic promoter, at least one non-native plant viral subgenomic promoter, a plant viral coat protein coding sequence, and optionally, at least one non-native nucleic acid sequence to be transcribed or expressed in the infected host plant. The recombinant plant viral nucleic acids are stable, capable of systemic infection and capable of stable transcription or expression in the plant host of the non-native nucleic acid sequences.