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Birds do it, bees do it, but Candida albicans does it differently.

Robinson R - PLoS Biol. (2008)

View Article: PubMed Central - PubMed

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For while it appears to be incapable of meiosis and therefore true sex, it engages in an unusual and offbeat alternative—after it mates, its progeny randomly cast off chromosomes to restore the diploid number, or something close to it... In a new study, Anja Forche, Richard Bennett, and colleagues show that this process generates significant genetic diversity, which is further amplified by recombination between homologous chromosomes, using a protein that is elsewhere used exclusively in meiosis... This “parasexual” cycle has only recently been discovered, and its details and genetic consequences have not been well characterized... The authors found that by manipulating the medium used to grow the yeast, they could induce stable tetraploids to undergo a reduction in their chromosome number... Colonies from cells with extra chromosomes generally grew more slowly than those of true diploids... Viability did not require both maternal and paternal chromosomes in the same cell—two copies of either would suffice, suggesting that many chromosomes do not harbor lethal recessive alleles, as has been proposed for C. albicans... Unexpectedly, the authors also found evidence that, in some strains, the remaining chromosomes had undergone homologous recombination, one of the hallmarks of meiosis... The authors showed that one such protein, Spo11p, which in other species cleaves double-stranded DNA as a prelude to meiotic recombination, was expressed in mitotically growing C. albicans... When the researchers deleted the gene, tetraploid cells could still reduce their chromosome number, but did not undergo recombination... These results indicate that in C. albicans, Spo11 cleaves double-stranded DNA to bring about recombination but, instead of occurring during meiosis, this happens during chromosome loss in the parasexual cycle... The authors propose that parasexuality may provide two advantages over the conventional meiotic sexual cycle, both tied to the yeast’s ability to survive within the mammalian host... First, the randomness of chromosome reduction and the high tolerance of the presence of three copies rather than two (or four) increases genetic variety, a potentially important feature for living in a dynamic environment such as the intestine... Second, the parasexual cycle avoids the production of spores, often the end result of fungal meioses.

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Configuration of the eight chromosomes of Candida albicans in a recombinant strain derived from the parasexual mating cycle.
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pbio-0060121-g001: Configuration of the eight chromosomes of Candida albicans in a recombinant strain derived from the parasexual mating cycle.


Birds do it, bees do it, but Candida albicans does it differently.

Robinson R - PLoS Biol. (2008)

Configuration of the eight chromosomes of Candida albicans in a recombinant strain derived from the parasexual mating cycle.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2365979&req=5

pbio-0060121-g001: Configuration of the eight chromosomes of Candida albicans in a recombinant strain derived from the parasexual mating cycle.

View Article: PubMed Central - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

For while it appears to be incapable of meiosis and therefore true sex, it engages in an unusual and offbeat alternative—after it mates, its progeny randomly cast off chromosomes to restore the diploid number, or something close to it... In a new study, Anja Forche, Richard Bennett, and colleagues show that this process generates significant genetic diversity, which is further amplified by recombination between homologous chromosomes, using a protein that is elsewhere used exclusively in meiosis... This “parasexual” cycle has only recently been discovered, and its details and genetic consequences have not been well characterized... The authors found that by manipulating the medium used to grow the yeast, they could induce stable tetraploids to undergo a reduction in their chromosome number... Colonies from cells with extra chromosomes generally grew more slowly than those of true diploids... Viability did not require both maternal and paternal chromosomes in the same cell—two copies of either would suffice, suggesting that many chromosomes do not harbor lethal recessive alleles, as has been proposed for C. albicans... Unexpectedly, the authors also found evidence that, in some strains, the remaining chromosomes had undergone homologous recombination, one of the hallmarks of meiosis... The authors showed that one such protein, Spo11p, which in other species cleaves double-stranded DNA as a prelude to meiotic recombination, was expressed in mitotically growing C. albicans... When the researchers deleted the gene, tetraploid cells could still reduce their chromosome number, but did not undergo recombination... These results indicate that in C. albicans, Spo11 cleaves double-stranded DNA to bring about recombination but, instead of occurring during meiosis, this happens during chromosome loss in the parasexual cycle... The authors propose that parasexuality may provide two advantages over the conventional meiotic sexual cycle, both tied to the yeast’s ability to survive within the mammalian host... First, the randomness of chromosome reduction and the high tolerance of the presence of three copies rather than two (or four) increases genetic variety, a potentially important feature for living in a dynamic environment such as the intestine... Second, the parasexual cycle avoids the production of spores, often the end result of fungal meioses.

No MeSH data available.


Related in: MedlinePlus