INTERFERENCE WITH BROME MOSAIC-VIRUS REPLICATION IN TRANSGENIC RICE

Rice protoplasts were transformed with four separate constructs derive d from the genome of brome mosaic virus (BMV) and regenerated into cal lus and plant lines, Constructs used for transformation were designed to yield (i) an artificial, defective, interfering RNA derived from RN A-2, (ii) a sense tRNA-like structure corresponding to the 3' end of R NA-2, (iii) an antisense sequence corresponding to the intercistronic region of BMV RNA-3, and (iv) RNA encoding the viral capsid protein, P rotoplasts obtained from transgenic plants or callus lines showed up t o 95% reduction in accumulation of progeny viral RNAs when inoculated with virion RNA. The addition of up to 20-fold the normal level of ino culum was required to overcome the induced resistance, The observed in terference appeared to be mediated through viral RNAs rather than prot ein products, but was not proportional to detectable levels of messeng er expression, suggesting the induction of a host defense mechanism.