Genomics and transcriptional analysis of the Neodiprion abietis nucleopolyhedrovirus




Duffy, Simon Paul

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Baculoviruses are a family of mostly insect-specific viruses with relatively complex infection pathology. The baculovirus genome encodes between 89-181 genes, that are regulated by a complex temporal cascade of gene expression. Although baculoviruses pathogenic to lepidopteran hosts are well characterized, relatively little is known about non-lepidopteran baculoviruses. This thesis provides the genome sequence of a baculovirus pathogenic to the balsam fir sawfly (order: Hymenoptera), the Neodiprion abietis nucleopolyhedrovirus (NeabNPV). Our analyses of the NeabPNV genome indicated that the regulation of NeabNPV early genes by immediate early transactivators may differ from the lepidopteran baculovirus model. Also, through genome sequence analysis, we propose a model for the evolution of sawfly baculoviruses that is mediated by interspersed genome repeats. By selecting key genes transcribed at distinct time points during baculovirus infection as well as quantifying viral DNA in the tissues of infected host larvae, we mapped the progression of NeabNPV infection in vivo. Based on the temporal scale of viral infection, we were able to show that two putative zinc-finger proteins, neab24 and neab52 are expressed in the immediate early and early stages of infection. The hypothesis that the mechanism of early gene regulation in non-lepidopteran baculovirus differs from that of lepidopteran baculoviruses prompted us to investigate promoter elements of 30 baculovirus genomes sequenced to date, in silica. This analysis revealed some sequence motifs may represent promoter elements in a wide range of baculoviruses, and that there may be differences in regulation of transcription between genes of the same temporal class in different baculovirus species.



baculoviruses, genetics, Balsam fir, diseases and pests