Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HaSNPV) and its closely related variant H. zea SNPV (HzSNPV) contain 20 open reading frames (ORFs) unique among baculoviruses. In this report, the function of HaSNPV ORF 122 (Ha122) is investigated. Ha122 was transcribed as a polyadenylated transcript from 8 h post-infection in infected H. armigera insect cells. 5'RACE analysis indicated that Ha122 transcription starts predominantly in the consensus major late transcription initiation motif DTAAG, around 47 nt upstream of the putative translation start codon, with a minor start at position -89. Using 3'RACE, the transcription stop site mapped 27 nt downstream of the putative translation stop codon. By Western blot analysis using a chicken-derived polyclonal antibody, the product of Ha122 was found in infected cells to be a 21 kDa protein, close to the theoretical size of 21.6 kDa. The Ha122 protein, when fused to green fluorescent protein, was observed in the nuclei of H. armigera cells but only in conjunction with wildtype HaSNPV infection. The 21 kDa. protein was located specifically in the nucleocapsid of occlusion-derived virions (ODVs) and not in that of budded virus. The available data suggest that Ha122 is a functional ORF of HaSNPV and HzSNPV and that the 21 kDa protein is a novel-specific component of baculovirus ODVs.
- exigua multicapsid nucleopolyhedrovirus
- envelope fusion protein