It's one of life's special moments: a child finds a fat caterpillar, puts it in a jar with a twig and a few leaves, and awakens one day to find the caterpillar has disappeared and an elegant but apparently lifeless case now hangs from the twig.
Then, when the jar has been forgotten, soft beating against its glass walls calls attention to a new wonder: the jar now holds a fragile-winged butterfly or dusky moth with fringed antennae.
These transformations are so startling that a child's awe seems a more appropriate response than an adult's calm acceptance.
How is it, after all, that an insect can remake itself so completely that it appears to be a different creature altogether, not just once, but several times in its lifetime?
Working with fruit flies rather than butterflies, a team led by Ian and Dianne Duncan of Washington University in St. Louis provides part of the answer in the latest issue of PNAS. Ian Duncan, PhD, is professor of biology in Arts & Sciences; Dianne Duncan is a research associate and director of the Biology Imaging Facility.
The puzzling question
Fruit flies go through three main life phases: the larva, the pupa, and the adult.
Earlier work had shown that the larval and adult forms are patterned by the same "signaling systems," or chains of biochemicals that transfer a signal from receptors on the surface of cells to target genes within cell nuclei.
What scientists didn't understand was how the same signaling systems could orchestrate the formation of a larva in one case and the adult fly in the other.
The Duncans, working with collaborator Eric Baehrecke, PhD, of the University of Massachusetts Medical School and graduate student Xiaochun (Joanna) Mou were able to show that a gene expressed only in the pupal stage redirects signaling systems so that they activate a different set of target genes than in earlier stages.
This gene is itself control
|Contact: Diana Lutz|
Washington University in St. Louis