Genomic and biological characterization of a new cypovirus isolated from Dendrolimus punctatus
Yin Zhou1, Tongcheng Qin1, Yuzhou Xiao1
1Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei, China.
Abstract:
A novel cypovirus (designated DpCPV-MC) was isolated from the pine moth Dendrolimus punctatus using serial in vivo cloning procedures. DpCPV-MC occurs in typical polyhedral occlusion bodies, containing a number of spherical virions. Laboratory bioassays indicated that the infectivity of DpCPV-MC against second-instar Spodoptera exigua larvae does not differ significantly from that of Dendrolimus punctatus cypovirus 1. Full-length amplification of the DpCPV-MC cDNAs identified 16 dsRNA genome segments. Each segment encodes one open reading frame with unique conserved terminal sequences at the 5' and 3' ends, which differ from those of all previously reported cypoviruses. On a phylogenetic tree based on the amino acid sequences of the polyhedrin of 19 cypovirus species, DpCPV-MC was closest to the type-4 cypoviruses. Homology searches showed that ten segments of DpCPV-MC (S1, S2, S3, S4, S5, S7, S8, S9, S12, and S13) encode putative CPV structural and nonstructural proteins, three segments (S6, S10 and S14) encode putative insect proteins or other viral proteins, and the other three segments (S11, S15, and S16) encode proteins that have no obvious sequence similarity to any known protein. Based on RNA secondary structures analysis, two segments of them (S11 and S16) were predicted to possibly transcript less efficiently than the other segments. We speculate that DpCPV-MC is composed of several genotypes. The ten CPV-related segments constantly exist in all genotypes, and one or two of the six CPV-unrelated segments co-exist with the ten CPV-related segments in one DpCPV-MC genotype, thus each virion contains no more than 12 segments. Based on our results and the literature, DpCPV-MC is a new cypovirus (Cypovirus 22, strain DpCPV-22).
Insights
A novel cypovirus, Dendrolimus punctatus cypovirus MC (DpCPV-MC), was identified from pine moths. This new virus, DpCPV-22, exhibits unique genome segments and infectivity similar to existing cypoviruses.
Area of Science:
- Virology
- Entomology
- Molecular Biology
Background:
- Cypoviruses are double-stranded RNA (dsRNA) viruses that infect insects.
- The pine moth Dendrolimus punctatus is a significant pest in forestry.
- Understanding viral diversity is crucial for developing effective pest control strategies.
Purpose of the Study:
- To isolate and characterize a novel cypovirus from Dendrolimus punctatus.
- To determine the genomic and phylogenetic properties of the new cypovirus.
- To compare its infectivity with known cypoviruses.
Main Methods:
- Serial in vivo cloning for virus isolation.
- Laboratory bioassays for infectivity testing.
- Full-length cDNA amplification and sequencing of dsRNA genome segments.
- Phylogenetic analysis based on polyhedrin amino acid sequences.
- Homology searches and RNA secondary structure analysis.
Main Results:
- A novel cypovirus, DpCPV-MC (Cypovirus 22, strain DpCPV-22), was isolated and characterized.
- DpCPV-MC has 16 dsRNA genome segments with unique terminal sequences.
- Its infectivity against Spodoptera exigua larvae is comparable to Dendrolimus punctatus cypovirus 1.
- Phylogenetic analysis places DpCPV-MC closest to type-4 cypoviruses.
- Ten segments encode known cypovirus proteins, while six encode uncharacterized proteins, suggesting potential genotypic variation.
Conclusions:
- DpCPV-MC represents a new species of cypovirus, DpCPV-22.
- The virus possesses a unique genome structure with potentially novel genes.
- Its genetic diversity may involve combinations of conserved and variable genome segments.
- Further research is needed to elucidate the function of the novel proteins and the implications of genotypic variation.
