RNA-dependent RNA polymerase isolated from cowpea chlorotic mottle virus-infected cowpeas is specific for bromoviral RNA.

An RNA-dependent RNA polymerase activity capable of synthesizing full length double-stranded RNA products only in the presence of bromoviral RNA templates has been isolated from cowpea chlorotic mottle virus (CCMV)-infected Cowpeas. No comparable discrete products were obtained when a nonbromoviral (cowpea mosaic virus) RNA was used as template. Heterodisperse, ribonuclease-sensitive products were obtained in reactions catalyzed by similar extracts from mock-inoculated (uninfected) plants in the presence of added CCMV RNA. The extraction procedure was identical to that used for obtaining virus-specific polymerase from brome mosaic virus-infected barley (Bujarski, Hardy, Miller, and Hall, Virology 119, 465-473, 1982). Comparison of the activities of the barley- and cowpea-derived enzymes provides further evidence for our contention that a virus-encoded polypeptide is an integral component of these replicases.