Summary auto-generated
Researchers isolated a previously unknown small RNA virus from laboratory-bred cotton bollworm larvae (Helicoverpa armigera), which they named H. armigera stunt virus (HaSV). The virus causes severe stunting and death in infected larvae within 1-8 days depending on developmental stage. HaSV particles are spherical (38 nm diameter) with a buoyant density of 1.296 g/ml and contain two non-glycosylated capsid proteins of 65,000 and 6,000 molecular weight. The viral genome consists of two non-polyadenylated single-stranded RNA segments (2.4 kb and 5.5 kb) with 5' cap structures and unblocked 3' termini. In vitro translation produced proteins near the maximum coding capacity of each RNA strand plus smaller proteins, without evidence of protein processing. Physicochemically, HaSV resembles Tetraviridae family members, particularly Nudaurelia ω virus, though no serological relationship exists. The bipartite genome structure and distinct capsid composition suggest HaSV represents a previously unrecognized virus group within or related to the Tetraviridae. The virus's specificity to lepidopteran insects raises potential applications for biological pest control of economically important moth species.
Key findings
- HaSV is a novel bipartite single-stranded RNA virus with 2.4 kb and 5.5 kb genome segments, distinguishing it from related viruses with smaller genomes
- The virus contains isometric 38 nm particles with two major capsid proteins (65K and 6K) that are non-glycosylated, and shows T=4 symmetry characteristic of Tetraviridae
- HaSV shares strong amino acid sequence identity with Nudaurelia ω virus capsid proteins (88-94%) but lacks serological cross-reactivity, suggesting a distinct virus group
- The viral RNA strands lack extensive polyadenylation and possess 5' cap structures with unmodified 3' termini, differing from nodavirus genome organization
- HaSV causes rapid pathogenicity in cotton bollworm larvae with potential applications for biological control of agricultural pest insects
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Abstract
A small RNA virus with novel characteristics has been isolated from laboratory-bred larvae of Helicoverpa armigera. Infection by the H. armigera stunt virus causes severe retardation of larval development and subsequent death. Its particles are isometric, 38 nm in diameter, and have a buoyant density of 1.296 g/ml in caesium chloride. The viral capsid has two major non-glycosylated protein components with Mrs of 65000 and 6000, and contains a genome composed of two non-polyadenylated single-stranded RNA molecules with lengths of 2.4 kb and 5.5 kb. The 5' termini of these RNAs are capped; their 3' termini are unblocked. In vitro translations of the viral RNAs showed synthesis of large proteins of sizes near the maximum coding capacity of each strand along with synthesis of numerous smaller proteins; no evidence for processing of precursors was seen. The physicochemical properties of the virus are most similar to those of the Nudaurelia ω virus, a provisional member of the Tetraviridae, although no antigenic relationship was observed between the two viruses. The bipartite genome and distinct capsid structure of these two viruses indicate the existence of a previously unrecognized virus group.