Canadian Forest Service Publications

Comparative genome sequence analysis of Choristoneura occidentalis Freeman and C. rosaceana Harris (Lepidoptera: Tortricidae) Alphabaculoviruses. 2013. Thumbi, D.K.; Béliveau, C.; Cusson, M.; Lapointe, R.: Lucarotti, C.J. PLOS One 8(7):e68968.

Year: 2013

Available from: Atlantic Forestry Centre

Catalog ID: 34842

Language: English

CFS Availability: PDF (download)

Available from the Journal's Web site.
DOI: 10.1371/journal.pone.0068968

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Abstract

The complete genome sequences of Choristoneura occidentalis and C. rosaceana nucleopolyhedroviruses (ChocNPV and ChroNPV, respectively) (Baculoviridae: Alphabaculovirus) were determined and compared with each other and with those of other baculoviruses, including the genome of the closely related C. fumiferana NPV (CfMNPV). The ChocNPV genome was 128,446 bp in length (1147 bp smaller than that of CfMNPV), had a G+C content of 50.1%, and contained 148 open reading frames (ORFs). In comparison, the ChroNPV genome was 129,052 bp in length, had a G+C content of 48.6% and contained 149 ORFs. ChocNPV and ChroNPV shared 144 ORFs in common, and had a 77% sequence identity with each other and 96.5% and 77.8% sequence identity, respectively, with CfMNPV. Five homologous regions (hrs), with sequence similarities to those of CfMNPV, were identified in ChocNPV, whereas the ChroNPV genome contained three hrs featuring up to 14 repeats. Both genomes encoded three inhibitors of apoptosis (IAP-1, IAP-2, and IAP-3), as reported for CfMNPV, and the ChocNPV IAP-3 gene represented the most divergent functional region of this genome relative to CfMNPV. Two ORFs were unique to ChocNPV, and four were unique to ChroNPV. ChroNPV ORF chronpv38 is a eukaryotic initiation factor 5 (eIF-5) homolog that has also been identified in the C. occidentalis granulovirus (ChocGV) and is believed to be the product of horizontal gene transfer from the host. Based on levels of sequence identity and phylogenetic analysis, both ChocNPV and ChroNPV fall within group I alphabaculoviruses, where ChocNPV appears to be more closely related to CfMNPV than does ChroNPV. Our analyses suggest that it may be appropriate to consider ChocNPV and CfMNPV as variants of the same virus species.

Plain Language Summary

Baculoviruses are viral pathogens of insects. They are characterized by rod-shaped viral particles embedded in protein occlusion bodies. Occlusion bodies are produced late in the viral replication cycle and are composed of either polyhedrin or granulin protein, hence the respective names nucleopolyhedrovirus (NPV) and granulovirus (GV). The western spruce budworm (Choristoneura occidentalis) is a major defoliator of Douglas fir and other conifers west of the Rocky Mountains. The obliquebanded leafroller (C. rosaceana) is a major economic pest of fruit trees throughout North America. The complete genome sequences of the western spruce budworm and oblique-banded leafroller NPVs (ChocNPV and ChroNPV, respectively) were determined and compared with each other and with those of other baculoviruses. ChocNPV and ChroNPV genomes exhibited high sequence similarities to each other and to spruce budworm (C. fumiferana) NPV (CfMNPV). The ChocNPV genome is more closely related to CfMNPV than ChroNPV. Analyses suggest that ChocNPV and CfMNPV may be variants of the same virus species. Genomic studies of Choristoneura baculoviruses provide important information on the prevalence and roles of baculovirus infections in different Choristoneura species, and the evolutionary relationships between these viruses and their hosts.

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