One need only recall the progression of caterpillar to butterfly to understand why metamorphosis in insects has been likened to a second stage of embryogenesis. Morphological changes between larva and adult are extensive, and because larvae, pupae and adults are accessible and large (relative to fertilized eggs and embryos), they are amenable to studies of the molecular events underlying important aspects of development. The study of insect physiology and development is significant for another, more specific reason. Insects can be agricultural pests and disease- carriers. Recent attempts have been made to find environmentally safe, non-toxic, biodegradable agents to control the more noxious insects. Among such agents are the very hormones that insects use to control their own development. The goal of this research is to understand how two hormones (20-hydroxyecdysone and juvenile hormone), with central roles in this process, act at the molecular level. Chironomids (including Chironomus thummi, the fly used in Dr. Bergtrom's research) contain high concentrations of the protein hemoglobin. In fact, the hemoglobins represent a large family of related-but-different proteins whose syntheses are regulated differentially during development. The regulation of specific hemoglobin synthesis is under the control of both 20-hydroxyecdysone and juvenile hormone. The molecular level at which each hormone either stimulates or represses specific globin production will be measured using cloned globin genes. The effects of the hormones will be analyzed both separately and together on levels and synthesis not only of the globin proteins themselves, but also the globin messenger RNAs (mRNAs) that are transcribed from globin genes and from which globin proteins are ultimately translated in the cell. By focussing on the dual hormonal regulation of single family related proteins, greater insight may be gained into how these hormones affect cellular processes in insects. Such data can contribute greatly to the confidence with which hormones (or their synthetic analogues) are used in insect control protocols, as well as to a more general understanding of molecular processes of animal development.
