Researchers discover how model organism Tetrahymena plays roulette with seven sexes
Scanning electron microscope view of two mating Tetrahymena cells. Credit: The ASSET (Advancing Secondary Science Education with Tetrahymena) Program at Cornell University
It's been more than fifty years since scientists discovered that the single-celled organism Tetrahymena thermophila has seven sexes. But in all that time, they've never known how each cell's sex, or "mating type," is determined; now they do. The new findings are published 26 March in the open access journal PLOS Biology.
By identifying Tetrahymena's long-unknown mating-type genes, a team of UC Santa Barbara biologists, with research colleagues in the Institute of Hydrobiology of the Chinese Academy of Sciences, and in the J. Craig Venter Institute, also uncovered the unusual process of DNA rearrangements needed for sex determination in this organism. The discovery has potential human health implications ranging from tissue transplantation to cancer, including allorecognitionthe ability of an organism to distinguish its own tissues from those of anotherwhich can be a first line of defense against infection and illness.
In the study, the scientists show that in this multi-sexed, single-celled organism, the sex of the progeny is randomly determined by a series of "cut and paste" genomic recombination events that assemble one complete gene pair and delete all others.
"We found a pair of genes that have a specific sequence which is different for each mating type," said Eduardo Orias, a research professor emeritus and part of the UCSB team. "They are very similar genesclearly related to one another, going back probably to a common ancestorbut they have become different. And each is different in a specific way that determines the mating type of the cell."
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http://phys.org/news/2013-03-tetrahymena-roulette-sexes.html