Gene organization and sequencing of the Choristoneura fumiferana defective nucleopolyhedrovirus genome

Abstract

Two distinct nucleopolyhedrovirus species of the eastern spruce budworm, Choristoneura fumiferana, exist in a symbiont-like relationship. C. fumiferana defective nucleopolyhedrovirus (CfDEFNPV) only infects C. fumiferana larvae per os in the presence of C. fumiferana nucleopolyhedrovirus Ireland strain (CfMNPV), but is infective when injected into the haemolymph. CfDEFNPV synergizes CfMNPV in per os infections and CfMNPV is always the predominant progeny. This study was undertaken to report the genomic makeup and organization of CfDEFNPV in an attempt to identify its defect and understand its synergistic role. The genome was mapped, sequenced, characterized and compared to other baculoviruses. The CfDEFNPV genome was 131 160 nt long with 149 putative open reading frames (ORFs) and a G+C content of 45?8 mol%. Homologues of all 62 conserved lepidopteran baculovirus genes were found including those implicated in per os infectivity, p74, per os infectivity factor (pif) and pif-2. Although no obvious deletions were observed to explain the defect, two ORFs, Cfdef79 and Cfdef99 (inhibitor of apoptosis-4), contained potential deletions. Cfdef50 (late expression factor-10)/Cfdef51 (vp1054) and Cfdef76/Cfdef77 (telokin-like protein) had large overlaps and a potential homologue to ac105/he65 was split. Four baculovirus repeat ORFs were present, as were two unique genes, but no enhancins were identified. CfDEFNPV contained 13 homologous regions, each with one to five palindromes. Comparison with fully sequenced baculovirus genomes identified CfDEFNPV as a group I NPV with the closest average amino acid identity to Epiphyas postvittana NPV, followed by Orgyia pseudotsugata MNPV and CfMNPV, with its closest matches being to individual Anticarsia gemmatalis MNPV gene sequences.

Mixed-genotype white spot syndrome virus infections of shrimp are inversely correlated with disease outbreaks in ponds

“…Even defective viruses, which often reduce the virulence of the virus population (e.g. Muñoz et al, 1998;Zwart et al, 2008), in some particular instances increase the virulence of the population when co-infecting with a helper virus (Lopez-Ferber et al, 2003;Lauzon et al, 2005). Here, however, we have identified a case were genetic heterogeneity is inversely correlated with disease outbreaks.…”

Analysis of the genome of Spodoptera frugiperda nucleopolyhedrovirus (SfMNPV-19) and of the high genomic heterogeneity in group II nucleopolyhedroviruses

“…More recently, genomes of NPVs that infect hymenopteran species were also sequenced (Garcia- Maruniak et al, 2004;Lauzon et al, 2004;Duffy et al, 2006). Analysis of the available genomes has shown that 29 genes are conserved in all baculoviruses sequenced so far (Herniou et al, 2003;Garcia-Maruniak et al, 2004;Lauzon et al, 2005). This group of core genes represent a relatively small part of the over 800 different orthologous gene groups found in all baculovirus genomes up to the present date (Jehle et al, 2006).…”

Dose dependency of time to death in single and mixed infections with a wildtype and egt deletion strain of Helicoverpa armigera nucleopolyhedrovirus

“…In the field, baculoviruses occur as mixtures of conspecific genotypes (Miller, 1997;Hodgson et al, 2001). This genotypic diversity in a baculovirus population can be the result of genetic drift from a single parent strain, due to mutations, deletions and insertions during virus replication, or it can result from mixing and recombination of local and immigrant baculovirus strains (Williams, and Otvos, 2005;Lauzon et al, 2005;Jakubowska et al, 2005). Molecular engineering methods have been used to generate novel baculovirus genotypes with improved traits, notably speed of kill.…”