Identification, sequence analysis and phylogeny of the lef-2 gene of Helicoverpa armigera single nucleocapsid baculovirus

The baculovirus late expression factor 2 (LEF-2) is involved in DNA replication, and most likely function as a primase processivity factor. Lef-2 genes have been found in multinucleocapsid nucleopolyhedroviruses (MNPVs) and in granuloviruses (GVs), but not yet in single-nucleocapsid NPV (SNPV). Here, a lef-2 gene homolog was identified from SNPV of Helicoverpa armigera (HearNPV). the open reading frame of the HearNPV lef-2 gene is 696 nucleotides long, encoding a putative protein of 232 amino acids with an M-r of about 26 kDa. the 5'-noncoding region contains two early (CAGT) consensus motifs for transcription initiation and three TATA boxes. Lef-2 transcripts started at a C, 29 nucleotides upstream of a putative translational start. A putative polyA signal, AATAAA, was found 76 nucleotides downstream of the translation stop codon. the HearNPV lef-2 gene has a low but significant degree of amino acid sequence identity (30%) to the lef-2 genes of 15 other baculoviruses of which nine were newly determined. the N-terminal half of the LEF-2 proteins: contains one (I) and the C-terminal half two (II and III) conserved domains. Sixteen amino acids are absolutely conserved in those LEF-2 investigated and are probably critical for LEF-2 function. A phylogenetic tree of 16 baculovirus LEF-2 proteins was constructed by using maximum parsimony analysis and appeared to be comparable: to a tree for ecdysteroid UDP-glucosyl transferases (Chen et al., 1997a). the genomic location of the lef-2 genes relative to polyhedrin/granulin and the clade structure of the gene trees suggest that genome organization and gene phylogeny are useful parameters to study the evolutionary history of baculoviruses. These two independent approaches also give a more complete picture of the ancestral relationship among baculovirus. (C) 1999 Elsevier Science B.V. All rights reserved.Agr Univ Wageningen, Dept Virol, NL-6709 PD Wageningen, NetherlandsChinese Acad Sci, Wuhan Inst Virol, Joint Lab Invertebrate Virol, Wuhan, Peoples R ChinaUniv Guelph, Dept Microbiol, Guelph, ON N1G 2W1, CanadaUniversidade Federal de São Paulo, Lab Retrovirol & Mol Biol, São Paulo, BrazilKyoto Inst Technol, Dept Appl Biol, Kyoto 606, JapanHebrew Univ Jerusalem, Fac Agr, Dept Entomol, IL-76100 Rehovot, IsraelUniv Calif Davis, Dept Entomol, Davis, CA 95616 USANatl Taiwan Univ, Dept Entomol, Taipei 10764, TaiwanMadurai Kamaraj Univ, Sch Biol Sci, Dept Genet, Madurai 625021, Tamil Nadu, IndiaUniversidade Federal de São Paulo, Lab Retrovirol & Mol Biol, São Paulo, BrazilWeb of Scienc