Genome Sequence of a Baculovirus Pathogenic for Culex nigripalpus

Abstract

In this report we describe the complete genome sequence of a nucleopolyhedrovirus that infects larval stages of the mosquito Culex nigripalpus (CuniNPV). The CuniNPV genome is a circular double-stranded DNA molecule of 108,252 bp and is predicted to contain 109 genes. Although 36 of these genes show homology to genes from other baculoviruses, their orientation and order exhibit little conservation relative to the genomes of lepidopteran baculoviruses. CuniNPV genes homologous to those from other baculoviruses include genes involved in early and late gene expression (lef-4, lef-5, lef-8, lef-9, vlf-1, and p47), DNA replication (lef-1, lef-2, helicase-1, and dna-pol), and structural functions (vp39, vp91, odv-ec27, odv-e56, p6.9, gp41, p74, and vp1054). Auxiliary genes include homologues of genes encoding the p35 antiapoptosis protein and a novel insulin binding-related protein. In contrast to these conserved genes, CuniNPV lacks apparent homologues of baculovirus genes essential (ie-1 and lef-3) or stimulatory (ie-2, lef-7, pe38) for DNA replication. Also, baculovirus genes essential or stimulatory for early-late (ie-1, ie-2), early (ie-0 and pe-38), and late (lef-6, lef-11, and pp31) gene transcription are not identifiable. In addition, CuniNPV lacks homologues of genes involved in the formation of virogenic stroma (pp31), nucleocapsid (orf1629, p87, and p24), envelope of occluded virions (odv-e25, odv-e66, odv-e18), and polyhedra (polyhedrin/granulin, p10, pp34, and fp25k). A homologue of gp64, a budded virus envelope fusion protein, was also absent, although a gene related to the other category of baculovirus budded virus envelope proteins, Ld130, was present. The absence of homologues of occlusionderived virion (ODV) envelope proteins and occlusion body (OB) protein (polyhedrin) suggests that both CuniNPV ODV and OB may be structurally and compositionally different from those found in terrestrial lepidopteran hosts. The striking difference in genome organization, the low level of conservation of homologous genes, and the lack of many genes conserved in other baculoviruses suggest a large evolutionary distance between CuniNPV and lepidopteran baculoviruses.

Induction of reaper ortholog mx in mosquito midgut cells following baculovirus infection

“…As the only dipteran baculovirus with genomic information, CuniNPV is distantly related to lepidopteran baculoviruses and lacks identifiable orthologs to many important genes such as the ie genes. 38 It is very likely that CuniNPV utilizes a yet unknown, but powerful, mechanism to block the apoptotic pathway downstream of mx activation.…”

On the classification and nomenclature of baculoviruses: A proposal for revision

“…The current classification of baculoviruses was challenged by the characterization of a NPV isolated from the dipteran Culex nigripalpus (CuniNPV) [30,2]. CuniNPV infects the midgut epithelial cells but no other tissues of mosquito larvae.…”

Pathology of aGammabaculovirusin Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host

“…Group I alphabaculoviruses, such as that of Autographa californica (AcMNPV), encode GP-64 [32] whereas group II NPVs, for example, Lymantria dispar LdMNPV, encode F-protein [33]. Sequence data have identified F-protein homologs in betabaculoviruses [34,35] and the Culex nigripalpus Deltabaculovirus (CuniNPV) [36], indicating that F-protein may be more ancestral in baculoviruses [37]. Further evidence of the restriction of gammabaculoviruses and deltabaculoviruses to gut tissues is the absence of viral fibroblast growth factor (vfgf) homologs [1] that aid the establishment of alphabaculovirus systemic infections [38][39][40].…”

“…Most control larvae were reared through until death or pupation to monitor for ambient levels of NeabNPV infection, whereas others were prepared for cytological examination at 48 and 96 h after feeding. Larvae fed on NeabNPV OBs were harvested at 0.5, 1, 2, 5, 8,12,18,24,36,48,60,72,96, and 120 h after inoculation (hpi). The methods for the preparation, sectioning, and viewing of Paraplast Plus (Sherwood Medical, St. Louis, Mo, USA) and epoxy (EponAraldite, Electron Microscope Sciences, Hatfield, PA, USA) embedded larval tissues have been detailed elsewhere [26].…”