Pathogen-derived resistance to a potyvirus: immune and resistant phenotypes in transgenic tobacco expressing altered forms of a potyvirus coat protein nucleotide sequence.

Transgenic Nicotiana tabacum 'Burley 49' plants containing one of six different forms of the tobacco etch virus (TEV) coat protein (CP) nucleotide sequence have been generated. In whole plant studies, R1 and R2 progeny were inoculated mechanically with TEV, and the appearance and severity of symptoms were recorded. Symptom phenotype was altered, ranging from near wild type susceptibility to apparent immunity. Protoplasts derived from wild type and transgenic Burley 49 plant lines were transfected with TEV RNA. Protoplasts from transgenic plants expressing full-length or truncated forms of TEV CP supported virus replication. Protoplasts from certain transgenic plants, producing plus- or minus-sense CP transcripts but no CP, did not support virus replication at wild type levels. A model is proposed to account for these observations.