The ecdysteroid UDP-glucosyltransferase (egt) gene of Momestra brassicae multinucleocapsid nucleopolyhedrovirus (MbHNPV) has been cloned and characterized. HbHNPV egt potentially encodes a protein of 528 amino acids. Analysis of the substrate specificity of the HbHNPV EGT protein showed that it mirrors that ofAutogropho californica HNPV (AcHNPV) EGT. HbHNPV EGT also appears to be secreted from infected cells. Confirmation that the cloned gene encodes an active EGT was obtained by transient

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... ssion assays. Phylogenetic trees of NPVs were generated based on the alignment of baculovirus EGT sequences. These phylogenies support the classification of MbHNPV as a group II NPV that is most closely related to Spodoptero exigua HNPV. Comparison of the EGTbased phylogenies with polyhedrin/granulin-based phylogenies shows that the position of AcHNPV is different in the two trees, possibly indicating that AcHNPV acquired its polyhedrin gene by recombination with another virus. Interest in insect baculoviruses has been stimulated by their potential as biological control agents and intensive research has focused on the improvement of their pesticidal properties by genetic engineering. Much of this effort has been directed at Autographa californica nucleopolyhedrovirus (AcMNPV). One approach taken has been the deletion of the AcMNPV egt gene. The egt gene product, ecdysteroid UDP-glucosyltransferase (EGT), catalyses the conjugation of insect ecdysteroid hormones with UDP-sugars (O'Reilly et al., I99I,