Genome Structure and the p10 Gene of the Helicoverpa armigera Nucleopolyhedrovirus

The genomic DNA of Helicoverpa armigera single-nucleocapsid nucleopolyhedrovirus (C1 clone) was digested with BamHI, EcoRV, HindIII, KpnI, PstI and XbaI, respectively, and formed 11, 31, 13, 6, 7, and 25 fragments larger than 400 bp, respectively. The size of genome was estimated to be about 130.7 kb. A detailed physical map was constructed for the six restriction enzymes. The five homologous region, hr1, hr2, hr3, hr4 and hr5, and the ten genes including polyhedrin gene (ph), immediate-early gene(ie1), p74, p10, chitinase gene, DNA directed DNA polymerase gene (DNApol), helicase gene, superoxide dismutase gene (sod), alkaline-exonuclease gene (alk-exo), ecdysteroid UDP-glucosyltransferase gene (egt) were identified and their locations in the genome were determined. The genome organization of HaSNPV is quite different from those of other NPVs ever determined. The p10 gene was located in the fragment BamHI-I(1.89 kb) with the transcriptional direction opposite to the polyhedrin gene. Upstream and downstream of the p10 gene were p26 and p74 gene, respectively. The transcriptional direction of p26 is the same as that of p10 gene, and opposite to that of the p74 gene. The ORF encoding p10 was 261 nucleotide long and encoding a putative 87 amino acid polypeptide of 9.3 kD. The immediate upsteam region of the p10 was an A-rich region, and aconserved TAAG motif, associated with transcriptional start sites in other p10 genes, was identified at a site 52 nucleotides upstream of the start codon ATG. A putative polyadenylation signal, AATAAA, was found 20 nucleotides downstream of the termination codon.