REPLICATION OF COWPEA MOSAIC-VIRUS RNA1 OR RNA2 IS SPECIFICALLY BLOCKED IN TRANSGENIC NICOTIANA-BENTHAMIANA PLANTS EXPRESSING THE FULL-LENGTH REPLICASE OR MOVEMENT PROTEIN GENES

Nicotiana benthamiana plants were transformed with either the cowpea m osaic virus (CPMV) RNA2-derived movement protein gene or the RNA1-orig inating replicase gene. For both types of genes, half of the R(2)-gene ration lines showed complete resistance when challenged with CPMV. Exp eriments using protoplasts revealed that the resistance operates at th e single cell level by specifically preventing replication of the RNA segment, from which the transgene was derived. In both cases, the resi stance acts against wild-type strain CPMV-Sb and the very homologous C PMV-S1 and CPMV-S8 strains, but not to other comovirus species includi ng cowpea severe mosaic virus (CPSMV). These data and the inability to detect transgene-encoded proteins, suggest an RNA-mediated nature of the resistance.