But how different creatures in the animal kingdom — from colorful birds and reef fish to butterflies and snakes — make and deploy their artful designs is one of nature’s deepest secrets. Now, however, a team of researchers from the Howard Hughes Medical Institute at the University of Wisconsin-Madison has exposed the fine details of how animals make new body ornamentation from scratch. The work, the result of years-long and laborious experimentation, is published April 7 in the journal Nature.
“How do you generate complex patterns? This is a question that has interested biologists for a really long time,” says Sean Carroll, a UW-Madison molecular biologist and the senior author of the Nature report. “In this case, we at first had no clue. But now we think we’ve figured out all the key ingredients and we believe they are generally applicable (to many animals).”
The new study is important because it is the first to provide concrete evidence for a long-hypothesized system for generating animal color patterns, be they stripes, spots or any of the myriad designs animals use to camouflage themselves or find a mate. In particular, the Wisconsin group is the first to identify a color-inducing morphogen, a diffusible protein that tells certain cells to make pigment. …
The role of the Wingless morphogen was detailed by the painstaking genetic manipulation of flies that took three years and the injection of nearly 20,000 fly embryos to accomplish. Complicating the project is the fact that Drosophila guttifera is little used in research and its genome has not been sequenced.
However, by inserting the Wingless gene into different parts of the fly’s genome, the team was able to successfully manipulate the decoration of the fly’s wing, creating stripes instead of spots, and patterns not seen in nature. “We can make custom flies,” notes Carroll. By manipulating the gene, “we can make striped flies out of spotted flies.”
In addition to working out the molecular details of how the fly colors its wings, Carroll’s group was also able to deduce the evolutionary history of wing coloring in Drosophila guttifera.
In short, says Carroll, the patterns found on the wings of Drosophila guttifera came about through the fly’s manipulation of the Wingless gene: “It evolved by simply turning this gene on in places where it hadn’t been on before.”
Although the study was conducted in a lowly fruit fly, the principles uncovered by Carroll’s group, he argues, very likely apply to many animals, everything from butterflies to boa constrictors. “This is animal color patterning, how they are generated, how they evolved.”