Summary auto-generated
This study mapped the genome of Heliothis armigera entomopoxvirus (HaEPV), a caterpillar pathogen, using restriction enzymes and determined it to be approximately 233 kilobase pairs in length. The researchers cloned and sequenced two important genes: the spheroidin gene, which encodes the major structural protein of viral occlusion bodies (spheroids), and the nucleoside triphosphate phosphohydrolase I (NPHI) gene. Comparative analysis showed that HaEPV spheroidin and NPHI proteins share 77-79% and 82-89% amino acid identity, respectively, with homologous proteins from other Genus B entomopoxviruses, but show more distant relationships with Genus A viruses and vertebrate poxviruses. The researchers provided the first experimental evidence for inverted terminal repeat elements in an entomopoxvirus genome and determined the genomic locations of multiple genes. Comparative mapping revealed that HaEPV maintains similar gene organization to other Genus B entomopoxviruses but differs substantially from chordopoxviruses in gene arrangement. The authors proposed a classification system organizing EPV genes into functional and evolutionary categories, which may facilitate understanding of viral genome organization and evolution within the Poxviridae family.
Key findings
- HaEPV genome is approximately 233 kb and contains inverted terminal repeat elements, providing first experimental evidence for ITRs in entomopoxviruses
- HaEPV spheroidin and NPHI genes are highly conserved among Genus B entomopoxviruses (77-89% amino acid identity) but divergent from other poxvirus genera
- Gene organization in HaEPV is largely conserved with other Genus B entomopoxviruses but differs substantially from chordopoxviruses, supporting a unique EPV genomic organization
- The 17K open reading frame located at genomic termini shows homology to chordopoxvirus proteins but lacks characteristic zinc-finger motifs found in some vertebrate poxvirus homologues
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Abstract
The genome of Heliothis armigera entomopoxvirus (HaEPV) has been mapped with four restriction endonuclease enzymes (BamHI, HindIII, PstI and XhoI), and its length estimated at 233 kbp. An EcoRI-generated HaEPV genomic fragment hybridized to all fragments identified as genomic termini, providing the first experimental evidence for the presence of terminal repeat elements in an EPV genome. The HaEPV spheroidin and nucleoside triphosphate phosphohydrolase I (NPHI) genes have been cloned and sequenced, and their deduced products shown to possess high levels of identity with homologues from other Genus B entomopoxviruses (EPVs). The genomic locations of these and other HaEPV genes and open reading frames have been determined; comparison of their locations with those of homologues in the Amsacta moorei EPV genome largely supports an hypothesis that the Genus B EPVs share a conserved genomic organization which differs from that of chordopoxviruses. It is proposed that genes of EPVs can be assigned to five actual or predicted homology-based groups, a categorization which is useful for directing and interpreting investigations of EPV gene functions and relationships.