A comparative study on the cell-free translation of the genomic RNAs of two aphid picorna-like viruses.

The genomic RNAs of aphid lethal paralysis virus (ALPV) and Rhopalosiphum padi virus (RhPV)--two distinct picorna-like viruses found in aphids [Williamson et al. (1988) J Gen Virol 69: 787-795]--were both efficiently translated in rabbit reticulocyte lysates. ALPV RNA was translated into primary products with molecular weights ranging from 92 kDa to 170 kDa. These underwent time-dependent post-translational cleavage to produce smaller polypeptides including some with molecular weights comparable to those of the viral structural proteins. A 92 kDa polypeptide as well as smaller proteins were immunoprecipitated with capsid protein antisera, indicating the presence of at least one large capsid subunit protein precursor. RhPV RNA was translated into products of molecular weights ranging from 45 kDa to 175 kDa. There was no evidence for time-dependent post-translation cleavage of RhPV translation products. However, a 60 kDa polypeptide was precipitated with antiserum to RhPV virions, indicating that at least one capsid protein of RhPV is derived by proteolysis of a precursor protein, like those of ALPV and most other picornaviruses.