Preexisting Patterns Guide Evolution’s Paintbrush
A cousin of the commonly studied fruit fly Drosophila melanogaster, Drosophila guttifera has 16 black spots and four gray swatches on each wing.
One of the enduring mysteries of the animal world is how colored patterns come to adorn different species’ skin, scales, or feathers. Now, a team led by Howard Hughes Medical Institute investigator Sean B. Carroll has discovered how wing spots evolved in a species of polka-dotted fruit fly.
The new studies show that pigment production in the wing is patterned according to the spatial distribution of a molecule that helps sculpt the shape of the body during development. The finding underscores the concept that evolution likes to tinker with existing genetic machinery to evolve new patterns and forms.
The new studies show that pigment production in the wing is patterned according to the spatial distribution of a molecule that helps sculpt the shape of the body during development. The finding underscores the concept that evolution likes to tinker with existing genetic machinery to evolve new patterns and forms.
“One lesson here is that complexity can be generated in pretty simple ways.”Sean B. Carroll
“When nature invents, it does so by using what is readily available,” says Carroll, also a professor of molecular biology and genetics at the University of Wisconsin, Madison. The new report is published in the April 7, 2010, issue of Nature.
Carroll has spent his career studying how evolution occurs at the genetic level, pinpointing many of the molecular changes that lead to new traits and new species. Most of Carroll's discoveries have come to light by studying the common fruit fly Drosophila melanogaster,the workhorse of modern molecular genetics. For the current study, though, Carroll and colleagues focused onDrosophila melanogaster's prettier cousin, a polka-dotted fly species called Drosophila guttifera. Unlike the rather plain D. melanogaster, which has spotless wings, each D. guttifera fly boasts 16 black spots and four gray swatches on each wing. Carroll says the pattern likely evolved to help the flies attract mates or to provide camouflage from predators.
In earlier research, Carroll's group traced the spots onD. guttifera to a pigment-producing gene called yellow. He also found that the wing spots appeared only after a particular genetic switch, called a regulatory element or an enhancer, switched on the yellow protein in specific cells. Regulatory elements bracket the coding regions of genes, and switch a gene on or off in particular tissues or at certain times during development. Much of Carroll’s research has explored the evolutionary role of these switches, finding that small changes in them can account for large differences in morphology and appearance.
For the new study, Carroll and his team discovered that all 16 spots on each wing are produced by a single enhancer region near the yellow gene. This discovery was a “great hint,” says Carroll, that a single molecule might act as an input that triggered the formation of all the spots. “If you had spots in one place governed by one piece of regulatory DNA and spots in another place governed by another piece of DNA, we would have been suspicious that there were different inputs and the pattern was sort of put together pell-mell,” says Carroll. “But the fact that there was one regulatory element made us think that there was one triggering molecule at play.”
In earlier research, Carroll's group traced the spots onD. guttifera to a pigment-producing gene called yellow. He also found that the wing spots appeared only after a particular genetic switch, called a regulatory element or an enhancer, switched on the yellow protein in specific cells. Regulatory elements bracket the coding regions of genes, and switch a gene on or off in particular tissues or at certain times during development. Much of Carroll’s research has explored the evolutionary role of these switches, finding that small changes in them can account for large differences in morphology and appearance.
For the new study, Carroll and his team discovered that all 16 spots on each wing are produced by a single enhancer region near the yellow gene. This discovery was a “great hint,” says Carroll, that a single molecule might act as an input that triggered the formation of all the spots. “If you had spots in one place governed by one piece of regulatory DNA and spots in another place governed by another piece of DNA, we would have been suspicious that there were different inputs and the pattern was sort of put together pell-mell,” says Carroll. “But the fact that there was one regulatory element made us think that there was one triggering molecule at play.”
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Read more here/Leia mais aqui: HHMI News
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NOTA CAUSTICANTE DESTE BLOGGER:
A complexidade nas coisas bióticas pode ser gerada em passos muito simples na natureza? Pago pra ver o processo gradual evolutivo responsável por esta complexidade.
"Guiar" não é um processo télico? Design Inteligente "guiando" a evolução?
"Guiar" não é um processo télico? Design Inteligente "guiando" a evolução?
