Defective interfering RNAs of a satellite virus

Panicum mosaic virus (PMV) is a recently molecularly characterized RNA viru s with the unique feature of supporting the replication of two subviral RNA s in a few species of the family Gramineae. The subviral agents include a s atellite RNA (satRNA) that is devoid of a coding region and the unrelated s atellite panicum mosaic virus (SPMV) that encodes its own capsid protein, H ere we report the association of this complex with a new entity in the RNA world, a defective-interfering RNA (DI) of a satellite virus, The specifici ty of interactions governing this four-component viral system is illustrate d by the ability of the SPMV DIs to strongly interfere with the accumulatio n of the parental SPMV. The SPMV DIs do not interfere with PMV satRNA, but they do slightly enhance the rate of spread and titer of PMV. The SPMV-deri ved DIs provide an additional avenue by which to investigate fundamental bi ological questions, including the evolution and interactions of infectious RNAs.