Origin of ecdysosteroid UDP-glycosyltransferases of baculoviruses through horizontal gene transfer from Lepidoptera

Abstract

Baculoviruses infecting Lepidoptera (butterflies and moths) encodes an enzyme known as ecdysosteroid UDP-glycosyltransferase (EGT), which inactivates insect host ecdysosteroid hormones, thereby preventing molt and pupation and permitting a build-up of the viral population within the host. Baculovirus EGT shows evidence of homology to insect UDP-glycosyltransferases (UGTs), and a phylogenetic analysis supported that the closest relatives of baculovirus EGT are the UGT33 and UGT34 families of lepidopteran UGTs. The phylogenetic analysis thus supported that baculovirus EGT arose by horizontal gene transfer of a UGT from a lepidopteran host, an event that occurred 70 million years ago at the earliest but possibly much more recently. Three amino acid replacements unique to baculovirus EGTs and conserved in all available baculovirus sequences were identified in the N-terminal region of the molecule. Because of their conservation, these amino acids are candidates for playing an important functional role in baculovirus EGT function.

Keywords:

• double-stranded DNA viruses
• horizontal gene transfer
• insect viruses
• UDP-glycosyltransferase

Acknowledgments

This research was supported by grant GM43940 from the National Institutes of Health.