U of M researchers discover how a brain hormone controls insect metamorphosis

December 03, 2009

A team of University of Minnesota researchers have discovered how PTTH, a hormone produced by the brain, controls the metamorphosis of juvenile insects into adults.

The finding, published in the Dec. 4 issue of Science, will help scientists understand how insect body size is programmed in response to developmental and environmental cues and offers the opportunity to develop a new generation of more environmentally safe ways to control agricultural pests as well as insects that carry human pathogens.

Scientists have known for 100 years that a brain-derived neuropeptide known as PTTH controls metamorphosis and although its specific sequence was identified 20 years ago, the way it signaled endocrine tissue has remained elusive until now.

"Understanding the signaling pathway that controls metamorphosis has been a long-term goal for many insect physiologists," says lead author Michael O'Connor, professor of genetics, cell biology and development at the University of Minnesota's College of Biological Sciences, where he holds the Ordway Chair in Developmental Biology.

Although humans don't undergo metamorphosis, passage from childhood through puberty and development of adult sexual characteristics is also regulated by a brain-derived neuropeptide that is controlled by genetics, environment and nutrition. Understanding how this process works in insects sheds light on human development.

"In its overall design, insect metamorphosis is very much like passage through puberty," O'Connor says. "From a biological point of view, both puberty and metamorphosis accomplish the same goal - to provide reproductive capacity for the species at the appropriate developmental time." The brain hormone becomes active when insects have reached a threshold body weight, which is also a trigger for human puberty.

Fruit flies and silk moths were used for the study; however, all insects that undergo complete metamorphosis appear to use this signaling system, O'Connor says. His next step is to learn how environmental and nutritional cues regulate the production of PTTH (prothoracicotropic hormone).
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O'Connor is one of the University of Minnesota's most distinguished researchers working in the biological sciences. In addition to holding the Ordway Chair, he is an Investigator with the Howard Hughes Medical Institute. After earning a B.S. in biochemistry from Brown University and his Ph.D. from Tufts University School of Medicine, he conducted postdoctoral studies in the laboratory of Welcome Bender at Harvard Medical School. The O'Connor lab focuses on determining how signaling systems control animal development and studies the roles of several different types of growth factors in both insects and mice.

Co-authors for the Science paper are U of M postdoctoral researchers Kim Rewitz and Naoki Yamanaka and Lawrence Gilbert, who is an emeritus biology professor at the University of North Carolina.

College of Biological Sciences faculty conduct research in all areas of biology, from molecules to ecosystems. Their work contributes to advances in medicine, renewable energy, agriculture and biotechnology. The college offers degree programs in biochemistry, molecular biology and biophysics; genetics, cell biology and development; ecology, evolution and (animal) behavior; plant biology; microbiology and neurosciences. Admission to undergraduate programs is highly competitive. The college received approximately 5,000 applications for 400 places in this year's freshman class.

University of Minnesota

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