Nucleotide sequence and transcript mapping of the HindIII F region of the Autographa californica nuclear polyhedrosis virus genome

The sequence of the Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus genome

The nucleotide sequence of the Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HaSNPV) DNA genome was determined and analysed. The circular genome encompasses 131,403 bp, has a G+C content of 39.1 mol% and contains five homologous regions with a unique pattern of repeats. Computer-assisted analysis revealed 135 putative ORFs of 150 nt or larger; 100 ORFs have homologues in Autographa californica multicapsid NPV (AcMNPV) and a further 15 ORFs have homologues in other baculoviruses such as Lymantria dispar MNPV (LdMNPV), Spodoptera exigua MNPV (SeMNPV) and Xestia c-nigrum granulovirus (XcGV). Twenty ORFs are unique to HaSNPV without homologues in GenBank. Among the six previously sequenced baculoviruses, AcMNPV, Bombyx mori NPV (BmNPV), Orgyia pseudotsugata MNPV (OpMNPV), SeMNPV, LdMNPV and XcGV, 65 ORFs are conserved and hence are considered as core baculovirus genes. The mean overall amino acid identity of HaSNPV ORFs was the highest with SeMNPV and LdMNPV homologues. Other than three 'baculovirus repeat ORFs' (bro) and two 'inhibitor of apoptosis' (iap) genes, no duplicated ORFs were found. A putative ORF showing similarity to poly(ADP-ribose) glycohydrolases (parg) was newly identified. The HaSNPV genome lacks a homologue of the major budded virus (BV) glycoprotein gene, gp64, of AcMNPV, BmNPV and OpMNPV. Instead, a homologue of SeMNPV ORF8, encoding the major BV envelope protein, has been identified. GeneParityPlot analysis suggests that HaSNPV, SeMNPV and LdMNPV (group II) have structural genomic features in common and are distinct from the group I NPVs and from the granuloviruses. Cluster alignment between group I and group II baculoviruses suggests that they have a common ancestor.

Sequence and organization of the Spodoptera exigua multicapsid nucleopolyhedrovirus genome

The nucleotide sequence of the DNA genome of Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV), a group II NPV, was determined and analysed. The genome contains 135611 bp and has a G+C content of 44 mol%. Computer-assisted analysis revealed 139 ORFs of 150 nucleotides or larger; 103 have homologues in Autographa californica MNPV (AcMNPV) and a further 16 have homologues in other baculoviruses. Twenty ORFs are unique to SeMNPV. Major differences in SeMNPV gene content and arrangement were found compared with the group I NPVs AcMNPV, Bombyx mori (Bm) NPV and Orgyia pseudotsugata (Op) MNPV and the group II NPV Lymantria dispar (Ld) MNPV. Eighty-five ORFs were conserved among all five baculoviruses and are considered as candidate core baculovirus genes. Two putative p26 and odv-e66 homologues were identified in SeMNPV, each of which appeared to have been acquired independently and not by gene duplication. The SeMNPV genome lacks homologues of the major budded virus glycoprotein gene gp64, the immediate-early transactivator ie-2 and bro (baculovirus repeat ORF) genes that are found in AcMNPV, BmNPV, OpMNPV and LdMNPV. Gene parity analysis of baculovirus genomes suggests that SeMNPV and LdMNPV have a recent common ancestor and that they are more distantly related to the group I baculoviruses AcMNPV, BmNPV and OpMNPV. The orientation of the SeMNPV genome is reversed compared with the genomes of AcMNPV, BmNPV, OpMNPV and LdMNPV. However, the gene order in the 'central' part of baculovirus genomes is highly conserved and appears to be a key feature in the alignment of baculovirus genomes.

Properties of a baculovirus mutant defective in the protein phosphatase gene

Autographa california nuclear polyhedrosis virus (AcMNPV) contains a gene, ptp, encoding a protein tyrosine/serine phosphatase, BV-PTP. To investigate the biological function of ptp in the baculoviral replication cycle, we constructed a recombinant baculovirus, vPTPdel, in which the catalytically active site of BV-PTP was deleted. Although the vPTPdel mutant was viable in cell culture, it was partially defective in occluded virus production in SF-21 but not TN-368 cell lines. SF-21 cells infected with vPTPdel were heterogeneous in their ability to support occluded virus production. These results suggest that BV-PTP functions in a cell line-specific and possibly a cell cycle-specific fashion. The yield of occlusion bodies, infectivity (concentration of virus causing 50% mortality) and virulence (the time at which 50% of the cells died) of vPTPdel appeared to be normal in insect larvae. We identified a 35-kDa phosphoprotein as a potential target of the BV-PTP in SF-21 cells.

A protein phosphatase related to the vaccinia virus VH1 is encoded in the genomes of several orthopoxviruses and a baculovirus

The vaccinia virus VH1 gene product is a dual specificity protein phosphatase with activity against both phosphoserine- and phosphotyrosine-containing substrates. We investigated the potential presence of VH1 analogs in other viruses. Hybridization and sequence data indicated that a phosphatase related to the VH1 phosphatase is highly conserved in the genomes of smallpox variola virus and other orthopoxviruses. The open reading frames from the raccoonpox virus and the smallpox variola virus Bangladesh major strain genomes encoding the VH1 analogs were sequenced and found to be highly conserved with the vaccinia virus VH1. An open reading frame from the baculovirus Autographa californica has sequence similarity to the VH1 phosphatase. The viral proteins appear to be structurally related to the cell cycle control protein p80cdc25. A recombinant phosphatase expressed from the baculovirus gene was found to share with the VH1 phosphatase the ability to hydrolyze substrates that contained both phosphoserine and phosphotyrosine.

The structural and functional organization of the Autographa californica nuclear polyhedrosis virus genome

Baculoviruses are used as biological control agents of insect pests in agriculture and forestry. The multiple-nucleocapsid nuclear polyhedrosis virus of Autographa californica (AcMNPV) is the prototype baculovirus. Recently, this virus has become widely used as vector for the high-level expression of foreign genes in insect cells. An updated physical map of restriction sites as well as the location of open reading frames (ORFs) and transcripts are presented. Most characteristic is the dispersal of "early", "late", and "very late" genes over the genome and the presence of nested sets of 3' and 5' coterminal transcripts.

Characterization of a baculovirus gene encoding a small conotoxinlike polypeptide

We identified a gene of Autographa californica nuclear polyhedrosis virus (AcMNPV) that encodes a small cysteine-rich polypeptide which has size and sequence similarity to omega-conotoxins, a class of calcium ion (Ca2+) channel inhibitors, found in the venom of cone snails. Transcriptional analysis indicated that the 159-bp open reading frame, which we named ctl, and a downstream 984-bp open reading frame are transcribed as a single 1.3-kb bicistronic late RNA. The mature ctl gene product was identified as a small secreted protein by high-pressure liquid chromatography fractionation of extracellular fluid. Viruses with a site-specific deletion in ctl appeared normal with regard to the kinetics and virulence of infection, both in vitro and in vivo. Although we studied the behavior of wild-type and mutant virus-infected insects in some detail, a biological role for ctl in AcMNPV infection remains to be established.

Nucleotide sequence of the Autographa californica nuclear polyhedrosis 9.4 kbp EcoRI-I and -R (polyhedrin gene) region

The nucleotide sequence of a 9.4-kbp region including the polyhedrin gene of the C6 strain of the Autographa californica nuclear polyhedrosis virus (AcMNPV) genome was determined. These data provide a complete description of the EcoRI-I fragment, which is used to produce transfer vectors for inserting foreign genes into the AcMNPV. Ten potential open reading frames (ORFs) were identified in the complete sequence, on either strand of DNA. The largest of these was 1629 nucleotides in length and was located downstream from the polyhedrin coding sequences, but on the opposite strand of DNA. Northern blot hybridization analysis of ORF 8 (1629) identified an RNA of 2000 nucleotides which was produced in infected cells from 12 hr p.i. and remained until at least 48 hr p.i. S1 nuclease mapping and analysis of cDNA clones located the 3' end of the mRNA at a site 16 nucleotides downstream of the polyhedrin coding sequences. The 5' end of the mRNA was mapped using primer extension analysis of polyadenylated RNA. The mRNA start site was positioned within a late/very late consensus transcription initiation motif (ATAAG), 428 nucleotides upstream from the potential ATG translation initiation codon. The biological significance of the putative gene product was assessed by inserting a synthetic oligonucleotide in the carboxyl terminal coding sequences of ORF 8 (1629) to prematurely terminate translation. Recombinant viruses containing this mutation were not isolated, suggesting that the ORF 1629 gene product is essential for virus replication.