NUCLEOTIDE-SEQUENCE ANALYSIS SHOWS THAT RHOPALOSIPHUM-PADI VIRUS IS AMEMBER OF A NOVEL GROUP OF INSECT-INFECTING RNA VIRUSES

Rhopalosiphum padi virus (RhPV) is an aphid virus that has been consid ered a member of the Picornaviridae based on physicochemical propertie s. The 10,011-nt polyadenylated RNA genome of RhPV was completely sequ enced, Analysis of the sequence revealed the presence of two open read ing frames (ORFs). The predicted amino acid sequence of ORF1, represen ting the first 6600 ne of the RhPV genome, showed significant similari ty to the nonstructural proteins of several plant and animal RNA virus es. Direct sequence analysis of the RhPV capsid proteins showed that O RF2, which represents the last 2900 nt, encodes the three structural p roteins (28, 29, and 30 kDa). The predicted amino acid sequence of ORF 2 is Very similar to the corresponding regions of Drosophila C virus, Plautia stali intestine virus, and to a partial sequence from the 3' e nd of the cricket paralysis virus genome. The sire Of initiation of pr otein synthesis for ORF2 could not be determined from the amino acid a nd nucleotide sequences. ORF1 is preceded by 579 nt of noncoding RNA a nd the two ORFs are separated by more than 500 nt of noncoding RNA. Li ke picornaviruses, these regions may function to facilitate the cap-in dependent initiation of translation of the two ORFs. These data sugges t that RhPV, Drosophila C virus, Plautia stali intestine virus, and pr obably cricket paralysis virus are members of a unique group of small RNA viruses that infect primarily insects. (C) 1998 Academic Press.