Analysis of the Ecdysteroid UDP-Glucosyltransferase Gene of Heliothis armigera Single-Nucleocapsid Baculovirus

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Abstract
An ecdysteroid UDP-glucosyltransferase (egt) gene was identified from the single (S) nucleocapsid nucleopolyhedrovirus of Heliothis armigera (HearNPV). In baculovirus-infected insects the viral enzyme (EGT) plays a pivotal role in abrogating the insect molting process. The open reading frame of the egt gene is 1545 nucleotides long, encoding a putative protein of 515 amino acids with a M r of 59.1. The 5′-noncoding region contains a putative early (CAGT) and late (TAAG) motif for transcription initiation, a transcription enhancer sequence (CGTCGC) and two TATA boxes. A putative polyA signal, AATAAA, was found downstream of the translation stop codon. A putative signal peptide of 21 residues was present at the N-terminus of the EGT. The HearNPV egt gene has a high degree of nucleotide and amino acid sequence homology to the egt genes of Buzura suppressaria SNPV and Spodoptera exigua MNPV. The HearNPV EGT shares ten conserved motifs with other EGTs. A phylogenetic tree of twelve baculovirus EGTs was constructed by using maximum parsimony analysis, suggesting that SNPVs do not form a separate clade within the baculovirus family.