Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

MBL scientists confirm evolutionary exception

21.01.2004


MBL researchers provide strong evidence that an ancient microbe thrives and evolves without sex



Biologists at the Josephine Bay Paul Center for Comparative Molecular Biology and Evolution at the Marine Biological Laboratory (MBL) have confirmed that a group of microscopic animals has evolved for tens of millions of years without sexual reproduction. Their results demonstrate a radical exception to the biological rule that abandonment of sexual reproduction is an evolutionary dead end.

While almost all multicellular organisms reproduce sexually, this form of reproduction is much less efficient than asexual reproduction (or mitosis) whereby females effectively make clones of themselves. Although asexual organisms often enjoy short-term success against their sexual ancestors, they are rarely found as higher-order taxa, implying that they cannot survive in evolutionary time.


While many hypotheses have addressed this problem, the paradox raises one of the most perplexing questions in biology: If asexual reproduction is more efficient than sexual reproduction, why does sexual reproduction predominate so thoroughly? New research from MBL evolutionary biologists may help scientists come closer to an answer.

In a paper to be published in next week’s Proceedings of the National Academy of Sciences (PNAS), MBL scientists Jessica Mark Welch and her colleagues David Mark Welch and Matthew Meselson provide the strongest evidence to date that a higher-ranking taxon has evolved without sexual reproduction.

The researchers studied the bdelloid rotifer, a microscopic animal found throughout the world in almost all aquatic habitats. Bdelloids appear to have given up sex 50 million years ago, yet the organism has evolved into 370 described species. While the researchers previously demonstrated that bdelloid genomes contain two or more divergent gene copies, an observation consistent with long-term asexual reproduction, a significant shortcoming of their approach was the inability to detect nearly identical gene pairs, as might result from inbreeding or other rare forms of sexual reproduction.

To overcome this methodical shortcoming and conclusively demonstrate that bdelloids are, in fact, completely asexual, Mark Welch and her colleagues painstakingly analyzed the genome of the bdelloid species, Philodina roseola. Using a method called fluorescent in situ hybridization, they scoured the genome, looking for chromosome partners, also called homologous pairs.

Identification of these would be a clear indication of sexual reproduction as each member of the chromosome pair is derived from a different parent.

The researchers identified four copies of a target P. roseola marker gene, however each gene was on a separate chromosome and all were quite a bit different from each other. These results, consistent with asexual reproduction, eliminate the possibility that bdelloids reproduce sexually and thus confirm that the organism has evolved without sexual reproduction or genetic exchange for tens of millions of years.

What drives early extinction, and why it can be averted by sex, remains one of the central mysteries of biology, the resolution of which is likely to have far-reaching impact on scientists’ understanding of basic biological and evolutionary processes. "Sex and genetic recombination are obviously tremendously important for life," says Jessica Mark Welch, "but we don’t understand why they are so important. When we do eventually understand, it could have practical consequences we can’t yet imagine."

Mark Welch and her colleagues will continue to study bdelloids as they offer an ideal model system in which to explore the effects of asexual reproduction. Their hope is to better understand how the animals have evolved without sexual reproduction and escaped extinction. "We can now use belloid rotifers to test the theories about why sex is important," says Mark Welch. "Any good theory will now have to account for why the bdelloids are an exception."

Note to Editors: The paper entitled "Cytogenetic evidence for asexual evolution of bdelloid rotifers" by Mark Welch, et al. is scheduled to be published in the PNAS Online Early Edition the week of 1/19/2004 to 1/23/2004. Related research entitled " When did gene copies in the asexual class Bdelloidea diverge?" by David Mark Welch, et al. will also appear in this issue


###
The Marine Biological Laboratory is an internationally known, independent, nonprofit institution dedicated to improving the human condition through creative research and education in the biological, biomedical and environmental sciences. Founded in 1888, the MBL is the oldest private marine laboratory in the Western Hemisphere. Learn more at http://www.mbl.edu.

The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution explores the evolution and interaction of genomes of diverse organisms that play significant roles in environmental biology and human health. This dynamic research program integrates the powerful tools of genome science, molecular phylogenetics, and molecular ecology to advance our understanding of how living organisms are related to each other, to provide the tools to quantify and assess biodiversity, and to identify genes and underlying mechanisms of biomedical importance. Projects span all evolutionary time scales, ranging from deep phylogenetic divergence of ancient eukaryotic and prokaryotic lineages, to ecological analyses of how members of diverse communities contribute and respond to environmental change. Three interlocking programs define the scope of research in the Bay Paul Center: the Program in Global Infectious Diseases, the Program in Molecular Evolution, and the Program in Molecular Microbial Diversity. Learn more at: http://www.mbl.edu/research/resident/lab_baypaul.html.

Gina Hebert | EurekAlert!
Further information:
http://www.mbl.edu
http://www.mbl.edu/research/resident/lab_baypaul.html

More articles from Life Sciences:

nachricht Lethal combination: Drug cocktail turns off the juice to cancer cells
12.12.2018 | Universität Basel

nachricht Smelling the forest – not the trees
12.12.2018 | Universität Konstanz

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

New discoveries predict ability to forecast dementia from single molecule

12.12.2018 | Health and Medicine

CCNY-Yale researchers make shape shifting cell breakthrough

12.12.2018 | Physics and Astronomy

Pain: Perception and motor impulses arise in the brain independently of one another

12.12.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>