Feb. 25, 2008
UI biologist helps discover novel organism adding to 'tree of life'
What can a tiny marine alga that resembles a little brown ball tell scientists about how different types of organisms are related on the family tree of all life on Earth?
Quite a bit, it turns out, when it stands at a critical junction where one form of life can provide a clear evolutionary connection between otherwise distant cousins, according to John Logsdon (left), associate professor of biology in the University of Iowa College of Liberal Arts and Sciences.
In the Feb. 21 issue of the journal Nature, Logsdon and his colleagues announced the discovery of a new type of eukaryotic algae that provides just such a bridge between two previously thought-to-be separate branches on the tree of life. Called Chromera velia, the organism is now the closest-known photosynthetic relative to apicomplexan parasites (like the malaria parasite, Plasmodium falciparum) -- much closer than their distant algal relatives called dinoflagellates (some of which cause harmful "red-tides"). Together, these unicellular organisms, along with ciliates (like Paramecium), are called "alveolates."
Logsdon said the find sheds light on a formerly dark corner of the evolution of photosynthesis and indicates that further, similar discoveries lie ahead. Also, this new organism will be a powerful model for studying parasitism and disease in Apicomplexa.
"Chromera opens new chapters in the evolutionary history of eukaryotic cells and will provide important clues to understand the biology of apicomplexan parasites and how they have evolved. In turn, this basic knowledge will be crucial in developing new therapeutics for the treatment of widespread diseases such as malaria and toxoplasmosis," said Logsdon.
Logsdon, who also directs the UI Roy J. Carver Center for Comparative Genomics, said the discovery is one more piece of a larger puzzle that seeks to fill in the picture of how all life on earth is interrelated.
He currently serves with UI biology professor Debashish Bhattacharya as co-principal investigator on a $1.6 million National Science Foundation (NSF) project "Assembling the Tree of Eukaryotic Diversity" that seeks to decipher the evolutionary relationships primarily among microbial eukaryotes. The collaborative project is part of a larger NSF-funded effort to construct a comprehensive family tree of life on Earth called "Assembling the Tree of Life."
Logsdon noted: "it's not often that we find an organism that fits on the tree of life as a major "missing link" of sorts. Quite often we are looking at relatives that, while sharing a clear common ancestor, have diverged into separate, distinct lineages. This was previously the case for Apicomplexa, which derive from photosynthetic ancestors, but are very distant from their formerly closest photosynthetic cousins, the dinoflagellates. Our study provides a clear demonstration that there is much left to discover and learn about the diversity of life on earth, especially in the microscopic world."
Logsdon's colleagues on the project include lead authors Robert B. Moore of the University of Sydney, Australia, where he did the initial work with senior author Dee A. Carter; and Miroslav Obornik of the Biology Center of the Academy of Sciences and the University of South Bohemia, Czech Republic. Moore is formerly of the UI Roy J. Carver Center for Comparative Genomics where he worked on this project in Logsdon's laboratory.
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