Frequent ploidy changes in growing yeast cultures
Ploidy is considered a very stable cellular characteristic. Although rare, changes in ploidy play important roles in the acquisition of long-term adaptations. Since these duplications allow the subsequent loss of individual chromosomes and accumulation of mutations, changes in ploidy can also cause genomic instability, and have been found to promote cancer. Despite the importance of the subject, measuring the rate of whole-genome duplications has proven extremely challenging. We have recently measured the rate of diploidization in yeast using long-term, in-lab experiments. We found that spontaneous diploidization occurs frequently, by two different mechanisms: endoreduplication and mating type switching. Despite its common occurrence, spontaneous diploidization is usually selected against, although it can be advantageous under some stressful conditions. Our results have implications for the understanding of evolutionary processes, as well as for the use of yeast cells in biotechnological applications.
KeywordsSaccharomyces cerevisiae Ploidy Haploid Diploid Homothallism Heterothalism Genome duplication Endoreduplication Homologous recombination
We thank present and past members of the Kupiec lab for support, ideas and technical help. This work was supported by Grants from the Minerva Stiftung, the Volkswagen Foundation and the Israel Science Foundation to MK and the Stanford Center for Computational, Evolutionary and Human Genomics to YR.
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