Open reading frame 94 of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus encodes a novel conserved occlusion-derived virion protein, ODV-EC43 Minggang Fang, 1 Hanzhong Wang, 1 Hualin Wang, 1 Li Yuan, 1 Xinwen Chen, 1 Just M. Vlak 2 and Zhihong Hu 1 Correspondence Zhihong Hu huzh@pentium.whiov.ac.cn 1 Join-Laboratory of Invertebrate Virology and Key Laboratory of Molecular Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, People’s Republic of China 2 Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands Received 12 April 2003 Accepted 11 July 2003 Open reading frame 94 (Ha94) of Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HaSNPV) is 1086 bp long and a homologue of Autographa californica multiple NPV ORF109. The gene is conserved among all baculoviruses whose genomes have been completely sequenced so far and is thus considered a baculovirus core gene. Ha94 transcripts were detected from 24 to 96 h post-infection (p.i.) of HzAM1 cells with HaSNPV. Polyclonal antiserum raised to a GST–HA94 fusion protein recognized a 43 kDa protein, HA94, in infected cell lysates from 36 to 96 h p.i., suggesting that Ha94 is a late gene. Western blot analysis of proteins present in budded virus and occlusion-derived virus (ODV) showed that Ha94 encodes a structural component of ODV. When ODVs were fractionated further into nucleocapsid and envelope components, Western blot analysis indicated that the encoded protein was associated with both the nucleocapsid and the envelope. In summary, data available indicated that Ha94 encodes a novel ODV-specific protein of HaSNPV, designated ODV-EC43. INTRODUCTION The Baculoviridae, a diverse family of more than 600 viruses, encompasses two genera, the Nucleopolyhedro- viruses (NPVs) and the Granuloviruses (GVs) (Blissard et al., 2000). These viruses are very specific and mainly infect insects of the orders Lepidoptera, Hymenoptera and Diptera, but always within the phylum Arthropoda. The family is characterized by the occlusion of virions into large proteinaceous capsules or occlusion bodies (OBs). NPVs have two morphotypes, SNPV and MNPV, depending on the single (S) or multiple (M) packaging of the nucleocapsids (NCs) into the envelope (E). Based on phylogenetic analysis, NPVs have been divided into groups I and II (Zanotto et al., 1993; Herniou et al., 2001). In a single infection cycle, two forms of virions are produced, the budded virus (BV) and the occlusion-derived virus (ODV). BVs are responsible for the spread of the virus from cell to cell in the larva host and ODVs initiate the infection in a susceptible host and are responsible for the horizontal spread of the virus in an insect population (Blissard et al., 2000). The structural components of BVs and ODVs, except for the circular double-stranded DNA, are different to accommodate their respective functions in an infection cycle (Braunagel & Summers, 1994). The molecular biology of baculoviruses has developed rapidly in the last two decades. To date, the complete sequences of 17 baculovirus genomes have been reported; they range in size from 101 to 179 kbp and are predicted to encode 109 to 181 open reading frames (ORFs). These viruses are Autographa californica MNPV (AcMNPV) (Ayres et al., 1994), Bombyx mori NPV (BmNPV) (Gomi et al., 1999), Culex nigripalpus NPV (CuniNPV) (Afonso et al., 2001), Epiphyas postvittana NPV (EppoNPV) (Hyink et al., 2002), Helicoverpa armigera SNPV (HaSNPV) (Chen et al., 2001), Helicoverpa zea SNPV (HzSNPV) (Chen et al., 2002), Lymantria dispar MNPV (LdMNPV) (Kuzio et al., 1999), Mamestra configurata NPV A (MacoNPV A) (Li et al., 2002b), MacoNPV B (Li et al., 2002a), Orgyia pseudotsugata MNPV (OpMNPV) (Ahrens et al., 1997), Rachiplusia ou NPV (RaouNPV) (Harrison & Bonning, 2003), Spodoptera exigua MNPV (SeMNPV) (IJkel et al., 1999), Spodoptera litura NPV (SpltNPV) (Pang et al., 2001), Cydia pomonella GV (CpGV) (Luque et al., 2001), Phthorimaea operculella GV (PhopGV) (GenBank accession no. NC_004062), Plutella xylostella GV (PxGV) (Hashimoto 0001-9291 G 2003 SGM Printed in Great Britain 3021 Journal of General Virology (2003), 84, 3021–3027 DOI 10.1099/vir.0.19291-0