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Tentacles test tenets of evolution

Novel genes, rather than regulatory DNA, underlie the evolution of morphological traits, according to research published today (Nov. 17) in __PLoS Biology__. The new linkurl:study;http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060278 reports that genes found in simple freshwater animals -- but not in any other evolutionary lineage -- can drive changes in body plan, and stokes the flames of a long-standing debate among evolutionary developmental biologist

By | November 18, 2008

Novel genes, rather than regulatory DNA, underlie the evolution of morphological traits, according to research published today (Nov. 17) in __PLoS Biology__. The new linkurl:study;http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0060278 reports that genes found in simple freshwater animals -- but not in any other evolutionary lineage -- can drive changes in body plan, and stokes the flames of a long-standing debate among evolutionary developmental biologists. "This is the first study that puts together comparative molecular evolution data and experimental data into a cohesive case for this mode of evolution," Günter Wagner, an evolutionary developmental biologist at Yale University, who was not involved in the research, told __The Scientist__. The underlying genetic basis of morphological adaptation has been hotly debated in the evolutionary developmental (evo-devo) field. On the one side, many argue that innovations in body plans stem from modifications in the spatial and temporal activity of well-conserved linkurl:regulatory DNA,;http://www.the-scientist.com/news/display/23246/ known as cis elements. Others, however, argue that adaptation and speciation originate from structural mutations in the protein-coding regions of genes themselves. Although many agree that both sorts of changes take place, the relative importance of each process has remained unclear. Now, a team led by linkurl:Thomas Bosch,;http://www.uni-kiel.de/zoologie/bosch/ an evo-devo biologist at the Christian Albrechts University in Kiel, Germany, has found that expression of a single gene drives major differences in tentacle formation between two closely related linkurl:freshwater polyps;http://www.the-scientist.com/article/display/12151/ of the genus__ linkurl:Hydra;http://www.the-scientist.com/article/display/19175/ __-- score one for the structural mutation camp. What's more, the tentacle-related gene was found only in __Hydra__, with no shared genes in other evolutionary lineages.

Hydra tentacle formation during budding

Bosch's team scanned all the messenger RNAs of two closely related __Hydra__ species for genes differentially expressed in the main polyp-specific structures -- tentacles, nematocysts, and the stalk. Their transcriptome-tracking turned up __Hym301__, a gene coding for a secreted protein that was expressed in the tentacles of one species and everywhere but the tentacles in the other species. By using transgenic and mutant Hydra that overexpressed __Hym301__, as well as RNA interference to silence __Hym301__, they showed that the gene affects the general timing and order in which tentacles arise in the different linkurl:cnidarians.;http://www.the-scientist.com/news/display/53364 Genes such as __Hym301__ that don't resemble known coding sequences in any other organisms -- known as "orphan" genes -- are thought to constitute around 5 to 10% of all genes across most taxonomic ranks, and, yet, geneticists have largely ignored them for two reasons. First, characterizing a gene of no known function is time-consuming and laborious. Second, many suspected that these genes had counterparts in other organisms, but limited data precluded their detection. "You can't ignore [orphan genes] anymore because databases are getting very complete," Bosch told __The Scientist__. "There are obviously evolutionary selective constraints on keeping them for millions of years... They can't just be nonsense genes that are lying around." Perhaps the best examples of orphan genes, noted Bosch, can be found in the innate immune system where organisms need highly self-specific defense mechanisms. He said he also has unpublished results of __Hydra__ anti-microbial peptide genes with no genetic equivalents outside the genus. Further, he points to human beta-defensin as another lineage-restricted antimicrobial peptide gene that is found only in mammals. "These novel genes are important for adapting an organism to its particular needs," Bosch said. "That's why these genes are not found outside [their] taxon." Caltech evo-devo biologist linkurl:Eric Davidson,;http://www.its.caltech.edu/~davidson/ who was not involved in the study, however, doesn't think that the results of the paper can be generalized to account for fundamental evolutionary processes in other organisms. "What makes [a] body plan is fundamentally and generally the deployment of regulatory genes, not the specialized downstream genes," he wrote in an E-mail. Wagner takes a more nuanced stance toward the study's implications, though. "It certainly doesn't undermine the fact that cis-regulatory changes are important in morphological evolution, but it broadens the horizon by showing that other mechanisms, including new genes, can contribute to morphological differences." Image courtesy of PLoS Biology
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Comments

Avatar of: Daniel Gaston

Daniel Gaston

Posts: 1

November 18, 2008

The study does not test the tenets of evolution, as was fully acknowledged within the article the acquiring of new genes, of changes in regulation and expression of developmental genes, and mutations in structural genes have all been acknwoledged to play roles in speciation and the debate is mostly about their relative importance.\n\nHeadlines of this sort, which shoot for the sexy, paradigm, hype-inducing style of science do a disservice to science as a whole, giving a very different impression about what is going on in science to those not in the field. Within evolutionary biology alone there is a huge problem of Creationists latching on to headlines and stories of this type to use as propaganda about "mounting evidence against evolution". Nevermind that the article itself, not the study especially, ever go in that direction.\n\nI'm a big fan of The Scientist but when reporting on science we need to be careful about how we report scientfici work.

November 18, 2008

As if science didn't have enough problems with the public opinion that scientists are constantly revising themselves and each other. This study in no way "tests the tenets of evolution." All it does is score another point for the novel gene side of evo devo. No paradigm shift. No huge controversy. Nothing hot and sexy that should rock the scientific world. Just one more point awarded. Thanks, The Scientist, you just scored another point against science in the popular culture's view.
Avatar of: c jones

c jones

Posts: 1

November 19, 2008

This article was very interesting, but I agree with the previous comments - the headline had nothing to do with the content. It was certainly misleading and almost tabloid in its tone. Exploring and testing the relative importance of two known evolutionary mechanisims is not the same as testing the tenets of evolution.
Avatar of: Nelson Thompson

Nelson Thompson

Posts: 12

November 20, 2008

If you can give uncorrelated titles to your articles, then I assume you are encouraging me to do the same with my comments. This is not a case of interpretation--the article did not mention the "tenets" of evolution in any way.\nAs for the article itself, it took four readings for me (a mere physicist) to fully understand the dense use of genetijargon, but having done that, I think it one of the best I've read in your magazine in months. An understanding of the genetic source(s) of body-plan will prove invaluable in convincing future generations that evolution is as "real" as Newton's laws of motion.
Avatar of: Alla Katsnelson

Alla Katsnelson

Posts: 17

November 20, 2008

Thanks for your comments about the headline of the article. Our intention with this and other headlines is to frame the story in an intriguing and thought-provoking way, drawing readers in. We may have gotten more carried away with alliteration than some readers would like... but this one is justified as the work does indeed examine a debated area in evolutionary biology. \n-Alla Katsnelson, news editor
Avatar of: DENNIS HOLLENBERG

DENNIS HOLLENBERG

Posts: 26

November 22, 2008

Pray, where is the horrified grousing and petty sniping when a James Watson repeats the wrong-headed and conventional gene-centric dogma that 'genes are the key to life'?\n\nAs any sophomore knows, not only do gene's not do anything, they don't even exist as the discrete things they are conventionally assumed to be. In the year 2008 there can be no doubt that the genetic patterns by which observed biological process is blindly attributed are the historical residues of the cell's constituents' responses to the effects of the microenvironment.\n\nGiven that, the real point of this article is, Through precisely what set of dynamics did the resulting novel genetic pattern come to exist? Only when people involved in this 'Business of Pursuing Grants' ("Science") leave behind 1950s' thinking and begin addressing these nuances will our collective view of the life sciences progress.\n\nCertainly biologists cannot profit from billiard-ball physicists predictably inane pronouncements about how we should view truly complex system behavior (as opposed to physicists' navel-gazing proscenium-like descriptions of nature).\n\nThis thought-provoking article's title provides appropriate distinction from the usual dogmatic dross pouring out of academia's tribal pretense.
Avatar of: Donald Duck

Donald Duck

Posts: 39

February 10, 2009

Basic format of article:\n\nShocking Title\n\nThe debate we heard of\n\nGloopidy glop changes the depitity boop, but others thing the krazam is more important in this process than the baloogazoid, acording to the renowned scientist gabosh charbim.\n\n The reason 'The Scientist' looks like the tabloids is because it is one. Some articles cater towards laymen like myself, introducing new ideas and a greater view of the world, while others cater towards actual scientists, going into precise details about minuscule details a layman might understand but couldn't care less about.\n\n There is nothing wrong with either approach, in fact nothing wrong for supplying both in the same magazine, but each article should be placed in its own camp. No tabloid titles for articles only people who take biology can understand. \n\n Frankly, though, a paragraph to describe the difference between the two methods of evolution and another for what this indicates would be nice.\n\nPS The most perfect creation adapts and takes care of itself. Why would He create life that doesn't evolve? Proving evolution will never disprove creationism.

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