Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/1998
Publication Date: N/A
Interpretive Summary: Barley yellow dwarf viruses (BYDVs) cause the most damaging virus disease of cereal crops. The viruses are spread from infected plants to healthy plants by aphids. Previous experiments showed that insecticides could reduce the amount of damage caused by BYDVs in oat fields by limiting secondary spread of the viruses. The aphids that transmit BYDVs also can be infected with viruses. One of these insect viruses, Rhopalosiphum padi virus (RhPV), infects the aphid species that is the most common vector of BYDVs in the central United States. RhPV infects a relatively narrow range of aphid species, which makes it suitable for use as a biological control agent. As a first step towards developing bio-insecticides based on RhPV, the ribonucleic acid chromosome of the virus was isolated and molecularly characterized. These experiments showed that RhPV is a member of a group of viruses that has never been found to infect vertebrate animals, but that is common in insects. Hence, biological insecticides produced from insect viruses like RhPV should have little impact on non-target animal species. In addition, these data provide a framework for other researchers for the development of targeted biological insecticides that could reduce reliance on chemical insecticides.
Technical Abstract: Rhopalosiphum padi virus (RhPV) is an insect virus that, based on physicochemical properties, has been considered a member of the picornaviridae. To understand the organization of the RhPV genome, its 10 kb genomic RNA was sequenced from cDNAs clones. Analysis of the sequence revealed the presence of two large open reading frames (ORFs). The predicted amino acid sequence of the ORF representing the first 6,600 nt of the RhPV showed significant similarity to the nonstructural proteins of several plant and animal viruses. The predicted amino acid sequence of the ORF representing the last 3,000 nt showed significant similarity to the structural proteins of hepatitis A virus and to a partial sequence from the 3' end of the cricket paralysis virus genome. Direct sequence analysis of RhPV capsid proteins confirmed that the second ORF encodes the RhPV structural proteins. Hence, the genome organization of RhPV is similar to that of the caliciviruses. However, RhPV expresses three capsid proteins like the picornaviruses rather than the single capsid protein expressed by caliciviruses. These data suggest that RhPV, and probably cricket paralysis virus, are members of a unique group of small RNA viruses that infect primarily insects.