NSF Award
0615525
PROJECT SUMMARY<br/><br/>Intellectual Merits<br/>"What causes insect metamorphosis to begin" and "What happens at the start of metamorphosis" are central issues in our understanding of insect metamorphosis but these questions have been almost completely overlooked. There are two reasons for this. First, the higher Diptera, including the dominant model insect species, the fruit fly Drosophila melanogaster, have evolved compressed life cycles that include a telescoping of metamorphic development all the way back to embryogenesis. Consequently, metamorphosis never appears to "star" in flies. Second, when metamorphosis begins early in the final larval instar as it does in the majority of holometabolous insects, the adult primordia are composed of small numbers of cells. Studies have focused instead on events that occur in the bulk of the larva at a somewhat later stage. Evidence is presented in the proposal that the initiation of metamorphosis involves the overcoming of juvenile hormone (JH) repression by an endocrine factor called Metamorphosis Initiating Factor (MIF). The roles of JH and MIF in the initiation of metamorphosis will be established through studies of the moth, Manduca sexta, the insect for which the endocrine control of metamorphosis is best characterized. Hormonal regulation of gene expression and cellular responses will be examined primarily through in vitro culture of the developing adult eye. Prior to the start of metamorphosis, these cells are fully differentiated larval skin cells and then switch to become the compound eye of the adult moth. Although the discovery that skin cells can transform to become eye cells is astonishing, nevertheless, it appears this developmental process may better exemplify the early steps in metamorph-osis for most insects than do events in the fruit fly with which we are so familiar.<br/><br/>Broader Merits<br/>There is significant relevance in the proposed studies for agriculture and medicine through potential development of insecticides. In addition, molecular mechanisms of early eye development are conserved in all animals and elucidation of the hormonal control of eye development during insect metamorphosis has broad relevance for our understanding of animal development as well as endocrinology. The applicant will continue a very strong commitment toward outreach, recruitment, training, and community education. The proposed studies are expected to significantly broaden our understanding of the regulation of insect metamorphosis and the findings will be communicated to the general public as well as the scientific community. Scientists and nonscientists of all ages and backgrounds find insect metamorphosis a particularly appealing issue. This attracts high school students, undergraduates, and graduate students from a variety of backgrounds to participate in the research program. Funds are requested to fully include undergraduates as well as graduate students in the proposed studies and it is anticipated they will continue to be coauthors on primary research papers.<br/>Funds are requested to maintain a colony of Manduca sexta. Because animals can be used for the proposed studies only at specific developmental stages, "extra" animals are a valuable resource for primary and secondary schoolteachers in the surrounding communities as well as for student laboratory courses at the host institution.
