THE EFFECT OF BACULOVIRUS INFECTION ON ECDYSTEROID TITER IN GYPSY-MOTH LARVAE (LYMANTRIA-DISPAR)

Insect baculovirus carries a gene referred to as egt. This gene encodes an enzyme known as ecdysteroid UDP-glucosyl transferase which catalyzes the sugar conjugation of ecdysteroids. Using a gypsy moth embryonic cell line EGT activity of Lymantria dispar nuclear polyhedrosis virus was identified. The effect of egt gene expression following virus infection in gypsy moth larvae was studied by determining the ecdysteroid titer in hemolymph. A radioimmunoassay (RIA) was used to determine the ecdysteroid titer and TLC coupled with RIA was used to estimate levels of conjugated and unconjugated ecdysteroids. Both the level and pattern of hemolymph ecdysteroid titer in virus-infected larvae are different from uninfected control insects. The hemolymph ecdysteroid titer of virus-infected insects never rise above basal level during larval to pupal molting. However, during fourth to fifth larval molting, the hemolymph of virus-infected larvae shows higher levels of ecdysteroids than controls. In these insects the proportion of the sugar conjugated form of ecdysone was found to increase as virus replication proceeded.