A novel low molecular weight ecdysiotropin in post-diapause, pre-hatch eggs of the gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae)

Abstract

Extracts of post-diapause, pre-hatch eggs of the gypsy moth, Lymantria dispar L. were examined for prothoracicotropic hormone (PTTH)-like activity using an in vitro assay involving last-instar prothoracic glands (PGs). The eggs were extracted in water, eluted from a low-pressure C 18-silica cartridge in 60% acetonitrile, and fractionated on a high-performance, size-exclusion column. The primary ecdysiotropic activity eluted with an estimated molecular weight of 2.1 kDa far below the 4–7 kDa size determined for the low molecular weight PTTHs (bombyxins). Dose-response analysis revealed that the maximum activation was reduced by 75% by organic solvent extraction, but the remaining activity retained the ability to maximally activate the PGs 10-fold in vitro. At least some of the ecdysiotropic activity in the post-diapause, pre-hatch egg is localized in the brain of the pharate larva, and this activity increases dramatically prior to hatch when eggs are incubated at 25°C.