| Baculoviruses are pathogenic to insects. Presently, their origin and evolutionary paths are not clearly understood. Using a baculovirus structural protein gene, gp41, that has been shown to be highly conserved among baculoviruses, the gene transcription, protein structure, genomic structure and phylogenetic relationships were studied.; Two complete gp41 nucleotide sequences from Spodoptera frugiperda multiple nucleocapsid nucleopolyhedrovirus (SfMNPV-2) and Anticarsia gemmatalis MNPV (AgMNPV-2D), and a partial gp41 gene from Lymantria dispar MNPV (LdMNPV), were sequenced.; Northern blot analysis showed that the SfMNPV-2 gp41 was a late gene expressed 12 hours post-infection. The gp41 promoter region contained three transcriptional start sites, two within a consensus transcriptional start site (TAAG) of baculovirus late genes, and the other located in a region where no consensus motif has been determined.; The comparison of nucleotide and amino acid sequences of the AgMNPV-2D with four other NPVs, Autographa californica MNPV (AcMNPV), Bombyx mori MNPV (BmMNPV), SfMNPV and Helicoverpa zea single nucleocapsid nucleopolyhedrovirus (HzSNPV), showed a minimum of 59% nucleotide identity and 70% amino acid similarity. Analysis of the hydrophobicity and protein secondary structure of gp41 revealed several conserved domains including eight {dollar}alpha{dollar}-helix, four loop, one {dollar}beta{dollar}-sheet and one transmembrane domains.; The analysis of the gp41 upstream and downstream regions from those five NPVs showed that they contained vlf-l gene, ORF 330, ORF 300, gp41 and ORF {dollar}>{dollar}667 positioned from right to left and with a similar arrangement in their genomic maps. Among these ORFs, the AgMNPV-2D shared 50 to 70% nucleotide identity and 60 to 90% amino acid similarity with the four other NPVs.; Six baculovirus genes including polyhedrin (polh), p10, gp41, gp64, DNA polymerase (dnapol) and ecdysteroid UDP-glucosyltransferase (egt), were used to reconstruct phylogenetic trees. The results confirmed that hymenopteran NPVs diverged earlier from lepidopteran granuloviruses (GVs) and lepidopteran NPVs, later lepidopteran GVs diverged from lepidopteran NPVs. The dnapol phylogenetic tree also showed that the baculoviruses had an independent evolutionary path from two other insect DNA viruses, Spodoptera ascovirus (SAV) and Choristoneura fumiferana entomopoxvirus (CbEPV). |
