Genomic organization of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus

Abstract

The genome organization of the Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (HearNPV) was investigated and compared to that of other baculoviruses. A detailed physical map was constructed for the restriction enzymes BamHI, BglII, EcoRI, HindIII, KpnI, PstI, SacI and XhoI. The 130.1-kilobase pairs (kb) long viral genome was cloned as restriction fragments into a plasmid library, which covered 97.5% of the viral genome. From this plasmid library about 45 kb of dispersed sequence information was generated. Fifty-three putative open reading frames (ORFs) with homology to ORFs of other baculoviruses were identified and their location on the genome of HearNPV was determined. The arrangement of the ORFs along the HearNPV genome is significantly different from the multiple-nucleocapsid NPVs, AcMNPV, BmNPV and OpMNPV, which have a highly collinear genome, and the granulovirus XcGV. In contrast the genomes of HearNPV and SeMNPV are highly collinear. This close relatedness between an MNPV and an SNPV is supported by the phylogeny of specific genes of these two viruses and suggests that the morphotype (S or M) is only a taxonomic and not a phylogenetic denominator. The data presented here also give further support to the view that the gene distribution along baculovirus genomes can be used as a character to describe baculovirus relatedness independent of gene phylogeny. Five homologous regions (hrs) were located on the genome of HearNPV. This is also the first report of the existence of hrs in SNPVs and this observation suggests that hrs are a common feature of baculovirus genomes.

A Novel Binary Mixture of Helicoverpa armigera Single Nucleopolyhedrovirus Genotypic Variants Has Improved Insecticidal Characteristics for Control of Cotton Bollworms

“…These results are in line with data from previous studies performed with different variants of HearSNPV, in which variants of similar pathogenicities presented marked differences in speed of kill (36,50). Generally, the fastest-killing variants tend to produce lower numbers of OBs in each infected insect, because insects die faster and feed and grow less during the incubation period of infection, and the virus has less time to replicate (50)(51)(52)(53). However, we observed that HearLB1 was highly productive, despite being one of the fastestkilling variants.…”

Identification of a Conserved Non-Protein-Coding Genomic Element that Plays an Essential Role in Alphabaculovirus Pathogenesis

“…As protein-coding sequences are under strong evolutionary constraint, the average level of amino acid identity between proteins shared by two genomes appears to be a robust measure of the whole-genome level of relatedness between the species being compared. This level of identity was found to be relatively low for particular pairs of Alphabaculovirus species, exemplified by HearSNPVG4-BmNPV and LyxyMNPV-AcMNPV, which exhibit 41% and 33% amino acid identity, respectively [77] [44]. In addition, a high variability in GC content and gene number (ranging from 118 to 169 genes) across Alphabaculovirus genomes, a relatively low proportion of homologous genes shared by all alphabaculoviruses (among them are 37 core and 14 Alphabaculovirus-specific genes) compared to the entire gene content of each genome [9], and a large number of rearrangements in the genomes of particular alphabaculoviruses [78] suggest that the Alphabaculovirus genus includes highly diverged species.…”

Characterization and phylogenetic analysis of the chitinase gene from the Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus

“…EcoRI-K was cloned into the pTZ19R vector (Gibco-BRL) and denoted as plasmid pCXW125 (Chen et al, 2000). The chitinase ORF and its flanking regions were sequenced in both directions by primer walking (Sanger et al, 1977).…”