Characterization, sequencing and phylogeny of the ecdysteroid UDP-glucosyltransferase gene from two distinct nuclear polyhedrosis viruses isolated from Choristoneura fumiferana

Abstract

The ecdysteroid UDP-glucosyltransferase (egt) gene isolated from a plaque-purified isolate of Choristoneura fumiferana multinucleocapsid nuclear polyhedrosis virus (CfMNPV) was compared to its homologue from a defective MNPV virus (CfDEF) present in wild type virus populations infecting the eastern spruce budworm, C. fumiferana. The egt genes were located in the same relative position within the virus genomes and their genomic location and arrangement were similar to that found in Autographa californica MNPV (AcMNPV) and Orgyia pseudotsugata MNPV (OpMNPV). The genes encoded 491 and 494 amino acid open reading frames respectively, and were 67% identical at the amino acid level and 74% identical at the nucleotide level. Transcripts of the egt of CfMNPV peaked around 12 h post-infection (p.i.) and disappeared after 36 h p.i. Transcripts of the egt of CfDEF peaked between 6 and 9 h p.i. and were not detected 24 h p.i. The egt from CfMNPV was more similar to the partially sequenced egt identified from OpMNPV, at the nucleotide and amino acid levels, than it was to the egt from the CfDEF, AcMNPV, Bombyx mori NPV, Lymantria dispar MNPV or Spodoptera exigua MNPV. Phylogenetic analysis of egt supported the baculovirus evolution scheme suggested by polyhedrin sequence analysis.