Oct. 16, 2007
UI biologist receives $1.1 million NIH grant to study sex and meiosis
Is a particular type of microscopic animal -- one thought to have reproduced asexually for at least 35-40 million years -- actually capable of having sex?
A University of Iowa biologist hopes that his answer to that question will help solve a long-standing mystery in evolutionary biology: Why do organisms reproduce by means of sex at all?
John Logsdon, associate professor in the UI College of Liberal Arts and Sciences Department of Biological Sciences and director of the Roy J. Carver Center for Comparative Genomics, has received a five-year, $1,128,500 research grant from the National Institutes of Health (NIH) to study sex and meiosis in asexual rotifers.
Logsdon notes that, like most animals, many rotifer species are capable of sexual reproduction. Bdelloid rotifers, however, consist entirely of females that reproduce asexually by parthenogenesis: they produce identical daughters directly from eggs without the need for fertilization. "Fossil evidence and molecular genetic studies suggest that bdelloids are 'ancient asexuals,' persisting for at least 35-40 million years without sex," he says.
"Since meiosis -- the process by which gametes or sexual cells receive half the number of chromosomes from each parent cell -- is central to sexual reproduction, the central goal of this research is to determine the presence of and study the evolution of meiosis-specific genes in genomes of sexual and bdelloid rotifers. Organisms possessing meiotic genes may be capable of meiotic sex," Logsdon says.
He adds that his analyses of rotifer meiotic genes will investigate evolutionary relationships and rates, compared to mitotic genes and related organisms that reproduce sexually. His analyses should enable him to determine whether the isolated genes are capable of functioning in sexual reproduction or, alternatively, in some other unexpected process.
"The results from this project will either support the remarkable status of bdelloid rotifers as ancient asexuals or they will provide genetic evidence suggesting the bdelloids are capable of meiosis and, possibly, sexual reproduction," he says. "Reproductive modes are crucial to the biology and population genetics of all organisms." He notes that sexual reproduction plays a key role in the long-term survival and success of most living organisms.
"Although asexual species often arise, they regularly go extinct due, in part, to deleterious mutation accumulation and the inability to adapt to changing environments," he says.
"Thus, the methods developed here have applications relevant to human health and disease. Our approach to infer the presence of meiosis will be relevant to studies of parasite resistance, epidemiology, and disease treatment and management," he says.
Logsdon's colleagues on the project include: David Mark Welch, assistant scientist at the Josephine Bay Paul Center, the Marine Biological Laboratory in Woods Hole, Mass.; and Andrew Schurko, postdoctoral scientist in Logsdon's laboratory.
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