GROWTH-BLOCKING PEPTIDE - AN INSECT BIOGENIC PEPTIDE THAT PREVENTS THE ONSET OF METAMORPHOSIS

Many species of parasitoid wasps can alter development of their hosts. The parasitoid wasp Cotesia (Apanteles) kariyai perturbs the endocrinological process of the host Pseudaletia separata that controls normal metamorphosis from larva to pupa. This developmental disturbance allows the parasitoid wasp to complete its larval growth and emerge while the host is still in the larval stage, otherwise the parasitoid larva would be trapped in the sclerotized pupal cuticle. A peptidergic factor, growth-blocking peptide (GBP), with repressive activity against juvenile hormone esterase has recently been found in the parasitized host larval hemolymph. GBP has been purified and its complete structure determined. Injection of GBP into unparasitized last instar larvae of the armyworm retards larval growth and, consequently, delays the onset of pupation of the larvae. The induction of GBP is indispensable for the parasitoid's success. Here, I review characteristics of GBP and consider its possible physiological functions and mode of action.