Genomic organization of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus

The genome organization of the Helicoverpa armigera single-nucleocapsid nuc leopolyhedrovirus (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 i nto a plasmid library, which covered 97.5% of the viral genome. From this p lasmid library about 45 kb of dispersed sequence information was generated. Fifty-three putative open reading frames (ORFs) with homology to ORFs of o ther baculoviruses were identified and their location on the genome of Hear NPV 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 XcG V. In contrast the genomes of HearNPV and SeMNPV are highly collinear. This close relatedness between an MNPV and an SNPV is supported by the phylogen y 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 pr esented here also give further support to the view that the gene distributi on along baculovirus genomes can be used as a character to describe baculov irus relatedness independent of gene phylogeny. Five homologous regions (hr s) 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.