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  current news   Press   selected story    
     
  31 January 2013  
  The 'obligate diploid' Candida albicans forms mating-competent haploids
 
 



Authors
Meleah A. Hickman1, Guisheng Zeng2, Anja Forche3, Matthew P. Hirakawa4, Darren Abbey1, Benjamin D. Harrison1, Yan-Ming Wang2, Ching-hua Su5, Richard J. Bennett4, Yue Wang2 and Judith Berman1,6.

1 - Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, Minnesota      55455, USA.
2 - Institute of Molecular and Cell Biology, Agency for Science, Technology & Research, Singapore      138673, Singapore.
3 - Bowdoin College, Brunswick, Maine 04011, USA.
4 - Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island      02912, USA.
5 - Department of Microbiology and Immunology, Taipei Medical University, Taipei, Taiwan.
6 - Department of Molecular Microbiology and Biotechnology, George Wise Faculty of Life Sciences Tel      Aviv University, Ramat Aviv, 69978 Israel.

Published in Nature on 30 January 2013.
To read article, please click here.
Please click here to see Press Release.

Abstract 
Candida albicans, the most prevalent human fungal pathogen, is considered to be an obligate diploid that carries recessive lethal mutations throughout the genome. Here we demonstrate that C. albicans has a viable haploid state that can be derived from diploid cells under in vitro and in vivo conditions, and that seems to arise through a concerted chromosome loss mechanism. Haploids undergo morphogenetic changes like those of diploids, including the yeast–hyphal transition, chlamydospore formation and a white-opaque switch that facilitates mating. Haploid opaque cells of opposite mating type mate efficiently to regenerate the diploid form, restoring heterozygosity and fitness. Homozygous diploids arise spontaneously by auto-diploidization, and both haploids and auto-diploids show a similar reduction in fitness, in vitro and in vivo, relative to heterozygous diploids, indicating that homozygous cell types are transient in mixed populations. Finally, we constructed stable haploid strains with multiple auxotrophies that will facilitate molecular and genetic analyses of this important pathogen.

Synopsis:

Figure Legend: Auxotrophic hapoid strains enable one-step gene deletions.
a, Series of strains constructed from a stable haploid isolate, GZY792 (MTLα, his4) was isolated after propagation for 30 passages, screening for ploidy by flow cytometry and selection of isolates that were consistently haploid. GZY803 (ura3Δ) was constructed by disruption of URA3 with HIS4. Other auxotrophies were generated by the URA-flipper approach50.
b, Flow cytometry of these auxotrophic strains.
c, Genes disrupted in one-step map to all eight chromosomes. Circles, centromere position.
d
, Cell morphology phenotypes of haploid mutants grown in minimal media (yeast) or media supplemented with 20% FBS at 37ºC (hyphae) are similar to phenotypes seen for the corresponding diploid null mutants.

For more information on Yue WANG's laboratory, please click here.