Analysis of a late gene, orf101 from Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus

Abstract

Abstract Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus open reading frame 101 (ha101) is 762 nts in length and encodes a 254 amino acid peptide with predicted 29 kDa molecular weight. The homologues of ha101 were explored using BLASTP searching tool in the updated GenBank/EMBL and SWISS-PROT databases. The results showed that the homologues of ha101 were present in all the completely sequenced lepidopteran nucleopolyhedroviruses and granuloviruses, suggesting that ha101 might be a functional gene associated with their lepidopteran hosts. Sequence alignment of ha101 and its homologues revealed that 10 amino acids were completely conserved. RT-PCR analysis of ha101 manifested that the transcript of ha101 was first detected at 24 hpi and remained detectable at up to 122 hpi, suggesting that ha101 was transcribed during late stages of infection. Ha101 was expressed using Bac to Bac system in Tn5B-1-4 cells. The product of ha101 expressed in Tn5B-1-4 cells was approximately 29 kDa, consistent with the predicted molecular weight, and the results were confirmed by western blot analysis. The subcellular localization indicated that ha101 was aggregated along nuclear envelope during the early stages of infection and spread out to the entire nucleus including virogenic stroma in late stages of infection, suggesting that ha101 may play a specific role in virion assembly process or virogenic stroma arrangement.