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Selective advantages of a parasexual cycle for the yeast Candida albicans


Zhang, N and Magee, BB and Magee, PT and Holland, BR and Rodrigues, E and Holmes, AR and Cannon, RD and Schmid, J, Selective advantages of a parasexual cycle for the yeast Candida albicans, Genetics, 200, (4) pp. 1117-1132. ISSN 1943-2631 (2015) [Refereed Article]

Copyright Statement

Copyright 2015 by the Genetics Society of America

DOI: doi:10.1534/genetics.115.177170


The yeast Candida albicans can mate. However, in the natural environment mating may generate progeny (fusants) fitter than clonal lineages too rarely to render mating biologically significant: C. albicans has never been observed to mate in its natural environment, the human host, and the population structure of the species is largely clonal. It seems incapable of meiosis, and most isolates are diploid and carry both mating-type-like (MTL) locus alleles, preventing mating. Only chromosome loss or localized loss of heterozygosity can generate mating-competent cells, and recombination of parental alleles is limited. To determine if mating is a biologically significant process, we investigated if mating is under selection. The ratio of nonsynonymous to synonymous mutations in mating genes and the frequency of mutations abolishing mating indicated that mating is under selection. The MTL locus is located on chromosome 5, and when we induced chromosome 5 loss in 10 clinical isolates, most of the resulting MTL-homozygotes could mate with each other, producing fusants. In laboratory culture, a novel environment favoring novel genotypes, some fusants grew faster than their parents, in which loss of heterozygosity had reduced growth rates, and also faster than their MTL-heterozygous ancestors—albeit often only after serial propagation. In a small number of experiments in which co-inoculation of an oral colonization model with MTL-homozygotes yielded small numbers of fusants, their numbers declined over time relative to those of the parents. Overall, our results indicate that mating generates genotypes superior to existing MTL-heterozygotes often enough to be under selection.

Item Details

Item Type:Refereed Article
Keywords:Candida albicans, mating, parasexual cycle, cryptic sexual cycle
Research Division:Biological Sciences
Research Group:Microbiology
Research Field:Microbial genetics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the biological sciences
UTAS Author:Holland, BR (Professor Barbara Holland)
ID Code:102982
Year Published:2015
Web of Science® Times Cited:14
Deposited By:Mathematics and Physics
Deposited On:2015-09-14
Last Modified:2017-10-30

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