iansmith
May25-04, 09:02 PM
Genes evolve rapidly but genomes don't, suggesting that space constraints play a role | By Cathy Holding
Genomes within a group of eukaryotic obligate intracellular parasites—the microsporidia—are changing very slowly, even as the genes within them are evolving at a "strikingly high" rate, according to a study in the latest edition of Current Biology. The evolution of eukaryotic genomes usually correlates with the rate of sequence evolution, but the results of this study show that genomes do not necessary evolve in a clock-like fashion, say the authors.
Patrick Keeling at the University of British Columbia and colleagues randomly sequenced 685,000 base pairs of the microsporidian Antonospora locustae genome. They compared the organization of 183 genes found there with the recently completed genome sequence of the distantly related human parasite Encephalitozoon cuniculi, also a microsporidium. The degree of conservation of gene order between the two species was measured as the percentage of gene couples—pairs of genes adjacent to each other—that were couples in both species.
In over 94 A. locustae gene couples, 13% were also adjacent in E. cuniculi, an additional 17% were close neighbors in E. cuniculi, and 43% of the A. locustae couples are located on the same chromosome in E. cuniculi. The level of gene order conservation between these microsporidia (13%) is almost 1.5-fold higher than that between Saccharomyces cerevisiae and Candida albicans—9%—ascomycetes that are the closest relative to the microsporidia and that the authors say can provide a valid comparison of the data.
http://www.biomedcentral.com/news/20040525/01
Genomes within a group of eukaryotic obligate intracellular parasites—the microsporidia—are changing very slowly, even as the genes within them are evolving at a "strikingly high" rate, according to a study in the latest edition of Current Biology. The evolution of eukaryotic genomes usually correlates with the rate of sequence evolution, but the results of this study show that genomes do not necessary evolve in a clock-like fashion, say the authors.
Patrick Keeling at the University of British Columbia and colleagues randomly sequenced 685,000 base pairs of the microsporidian Antonospora locustae genome. They compared the organization of 183 genes found there with the recently completed genome sequence of the distantly related human parasite Encephalitozoon cuniculi, also a microsporidium. The degree of conservation of gene order between the two species was measured as the percentage of gene couples—pairs of genes adjacent to each other—that were couples in both species.
In over 94 A. locustae gene couples, 13% were also adjacent in E. cuniculi, an additional 17% were close neighbors in E. cuniculi, and 43% of the A. locustae couples are located on the same chromosome in E. cuniculi. The level of gene order conservation between these microsporidia (13%) is almost 1.5-fold higher than that between Saccharomyces cerevisiae and Candida albicans—9%—ascomycetes that are the closest relative to the microsporidia and that the authors say can provide a valid comparison of the data.
http://www.biomedcentral.com/news/20040525/01