Fungal biology: Finding yeast's better half

Jul 31, 2013
Fungal biology: Finding yeast’s better half
Through a process known as concerted chromosome loss, Candida albicans cells (pictured) containing two sets of chromosomes can form mating-competent and viable cells that contain a single set of chromosomes. Credit: Hemera/Thinkstock

Scientists long believed that the fungal pathogen Candida albicans was incapable of producing haploid cells—which contain only one copy of each chromosome, analagous to eggs and sperm—for mating. Mixing of genes in sexual reproduction helps generate the diversity that is the raw material for evolution, and C. albicans' inability to reproduce sexually appeared to give it a disadvantage. An international research team, including Yue Wang at the A*STAR Institute of Molecular and Cell Biology in Singapore, has now found viable haploid strains of C. albicans. The finding illuminates C. albicans' evolution and pathogenicity.

The team's discovery of the haploids was serendipitous. Team members in Ching-Hua Su's laboratory at the Taipei Medical University, Taiwan, studying C. albicans strains growing in media containing an , noticed a strain with half the usual amount of genetic material. Further analysis revealed that the strain lacked one of each of its eight chromosomes, indicating that it was in fact haploid.

Work in Wang's laboratory at A*STAR and in Judith Berman's laboratory at the University of Minnesota in the United States, revealed many strains of both in vitro and in vivo haploids. Not only could the haploids form all of the same developmental stages as their diploid counterparts, they formed cells that could mate.

The haploid cells were less fit than diploid cells: they grew slowly and were avirulent in mice. They were also ephemeral as after a short time in culture, they duplicated their own genetic material to become diploid. These so-called auto-diploids were also less virulent than wild-type cells. When two haploids mated, however, they produced diploid cells with a mixed and increased virulence and growth.

"Generation of haploid cells through random loss of chromosomes followed by mating between haploid cells of opposite sex generates , which is important for adaptation and evolution of this fungus," explains Wang.

The haploids will serve as an invaluable research tool in genetic and drug-discovery studies. Studying gene function in a diploid organism requires deleting both copies of a gene, which is technically very difficult, Wang notes. Researchers will now be able to delete genes in a single step.

Wang's team painstakingly screened thousands of isolates to identify several stable haploid strains. From these, they constructed a set of strains that will make genetic manipulation rapid and effective. "Preliminary screens of a small number of mutants have already identified several new genes important for virulence, promising more discoveries in the near future," says Wang.

Explore further: Researcher among best in protein modeling contests

More information: Hickman, M. A., et al. The 'obligate diploid' Candida albicans forms mating-competent haploids. Nature 494, 55–59 (2013).… abs/nature11865.html

Related Stories

Yeast 'rewired' to mate when starving

Dec 17, 2010

( -- New research has found that the mating habits of the dairy yeast depends on the levels of nutrients available as well as the availability of cells of the opposite "sex."

Plants cloned as seeds

Feb 17, 2011

Plants have for the first time been cloned as seeds. The research by aUC Davis plant scientists and their international collaborators, published Feb. 18 in the journal Science, is a major step towards making hybrid crop p ...

Recommended for you

Researcher among best in protein modeling contests

57 minutes ago

A Purdue University researcher ranks among the best in the world in bioinformatics competitions to predict protein structure, docking and function, making him a triple threat in the world of protein modeling.

Survey of salmonella species in Staten Island Zoo's snakes

2 hours ago

For humans, Salmonella is always bad news. The bacterial pathogen causes paratyphoid fever, gastroenteritis and typhoid. But for snakes, the bacteria aren't always bad news. Certain species of Salmonella are a natural part ...

A long-standing mystery in membrane traffic solved

Mar 27, 2015

In 2013, James E. Rothman, Randy W. Schekman, and Thomas C. Südhof won the Nobel Prize in Physiology or Medicine for their discoveries of molecular machineries for vesicle trafficking, a major transport ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.