The Genome of Gryllus bimaculatus Nudivirus Indicates an Ancient Diversification of Baculovirus-Related Nonoccluded Nudiviruses of Insects

Abstract

The Gryllus bimaculatus nudivirus (GbNV) infects nymphs and adults of the cricket Gryllus bimaculatus (Orthoptera: Gryllidae). GbNV and other nudiviruses such as Heliothis zea nudivirus 1 (HzNV-1) and Oryctes rhinoceros nudivirus (OrNV) were previously called "nonoccluded baculoviruses" as they share some similar structural, genomic, and replication aspects with members of the family Baculoviridae. Their relationships to each other and to baculoviruses are elucidated by the sequence of the complete genome of GbNV, which is 96,944 bp, has an AT content of 72%, and potentially contains 98 predicted protein-coding open reading frames (ORFs). Forty-one ORFs of GbNV share sequence similarities with ORFs found in OrNV, HzNV-1, baculoviruses, and bacteria. Most notably, 15 GbNV ORFs are homologous to the baculovirus core genes, which are associated with transcription (lef-8, lef-9, lef-4, vlf-1, and lef-5), replication (dnapol), structural proteins (p74, pif-1, pif-2, pif-3, vp91, and odv-e56), and proteins of unknown function (38K, ac81, and 19kda). Homologues to these baculovirus core genes have been predicted in HzNV-1 as well. Six GbNV ORFs are homologous to nonconserved baculovirus genes dnaligase, helicase 2, rr1, rr2, iap-3, and desmoplakin. However, the remaining 57 ORFs revealed no homology or poor similarities to the current gene databases. No homologous repeat (hr) sequences but fourteen short direct repeat (dr) regions were detected in the GbNV genome. Gene content and sequence similarity suggest that the nudiviruses GbNV, HzNV-1, and OrNV form a monophyletic group of nonoccluded double-stranded DNA viruses, which separated from the baculovirus lineage before this radiated into dipteran-, hymenopteran-, and lepidopteran-specific clades of occluded nucleopolyhedroviruses and granuloviruses. The accumulated information on the GbNV genome suggests that nudiviruses form a highly diverse and phylogenetically ancient sister group of the baculoviruses, which have evolved in a variety of highly divergent host orders.

Bombyx mori nucleopolyhedrovirus BmP95 plays an essential role in budded virus production and nucleocapsid assembly

“…BmNPV BmP95 and its homologues are conserved and encoded by all baculoviruses and are also found in nudiviruses (Wang et al, 2007) and probably in several insect genomes, such as that of Anopheles gambiae (Rohrmann, 2011). However, the function of BmP95 in the baculovirus life cycle remains largely unknown.…”

Paleozoic origin of insect large dsDNA viruses

“…Among these species, three nudivirus genomes have been fully sequenced [HzNV (47), Gryllus bimaculatus nudivirus (GbNV) (48), and Oryctes rhinoceros nudivirus (OrNV) (16)] and one has been partially sequenced (PmNV). Four species representative of each genus of the baculovirus family were chosen: Culex nigripalpus nucleopolyhedrovirus (CuniNPV) (49), Neodiprion lecontei nucleopolyhedrovirus (NeleNPV) (50), Autographa californica multiple nucleopolyhedrovirus (AcMNPV) (51), and Cydia pomonella granulovirus (CpGV) (52).…”

Two viruses that cause salivary gland hypertrophy in Glossina pallidipes and Musca domestica are related and form a distinct phylogenetic clade

“…The percentage of amino acid identity between the GpSGHV and MdSGHV ORFs and the size of the compared amino acid regions were also annotated. Since the SGHVs share general characteristics with the non-occluded insect nudiviruses and shrimp nimaviruses, the genomes from Heliothis zea 1 nudivirus (HzNV-1) (Cheng et al, 2002), Gryllus bimaculatus nudivirus (GbNV) (Wang et al, 2007b), Oryctes rhinoceros nudivirus (partial sequence) (Wang et al, 2007c) and the shrimp white spot syndrome virus (WSSV) (van Hulten et al, 2001) were also compared to MdSGHV and GpSGHV separately. Also in this case, homology was only accepted when the BLASTP E-values were lower than 0.01.…”