PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Yeast's lifestyle couples mating with meiosis

2014-01-06
(Press-News.org) Contact information: David Orenstein
david_orenstein@brown.edu
401-863-1862
Brown University
Yeast's lifestyle couples mating with meiosis

PROVIDENCE, R.I. [Brown University] — From a biological point of view, the world's most exotic sex lives may be the ones lived by fungi. As a kingdom, they are full of surprises, and a new one reported in the journal Nature seems sure to titillate the intellects of those who study the evolution of mating and ploidy, the complement of chromosomes in each cell.

Fungal fecundity is a seemingly anything goes world. Individual yeasts reserve the option of either sexual or asexual reproduction. Biologists remain puzzled about why, but different species predominantly maintain cells containing one (haploidy), two (diploidy), or three or more (polyploidy) versions of their chromosomes. Contrast that with the humdrum reproduction of animals who are locked into an unwavering program of sex and two versions of chromosomes in most cell types, except eggs, sperm and some others. Scientists look to yeasts to study the true variety of reproduction in the natural world.

"Fungi, in terms of sexual reproduction, are on the outer limits with what they can do, when they do it, and how they do it," said study corresponding author Richard Bennett, associate professor in Brown University's Department of Molecular Microbiology and Immunology. "There is a lot of super interesting biology in studying fungal sex. They keep surprising us."

In a study Bennett's lab published online in October in the journal Eukaryotic Cell, for example, a team led by undergraduate Riyad Seervai found that when Candida tropicalis mates, it turns diploid cells into tetraploid cells. But then it uses a mechanism other than meiosis to reduce the chromosome complement back to that of a diploid. This work was highlighted in print earlier this month.

Paired programs

In the new study in Nature, Bennett's team, including lead authors Christine Scaduto and Raquel Kim Sherwood (now at Yale), focused on the infectious species Candida lusitaniae, which unlike many Candida species happens to prefer a haploid "lifestyle." The scientists compared how its gene expression regulates mating and meiosis — the process of producing haploid cells from diploid cells – to that of a related diploid yeast, Saccharomyces cerevisiae, a.k.a. brewer's yeast.

Previous studies had shown that the brewer's yeast regulates meiosis and mating independently. The genes relevant to each process are transcribed and expressed when their specific process is underway. What the researchers discovered in C. lusitaniae, however, is that the yeast expressed genes associated with meiosis and mating during both processes. Their mating and meiosis programs were essentially fused.

"What was surprising was that when we started doing the transcriptional profiling experiments to see how genes are expressed, we weren't seeing this delineation of two programs," Bennett said. "We were seeing genes that that should have been expressed in mating only were also being expressed in meiosis and genes that should have been expressed in meiosis only were expressed in mating. In none of the other closely related species that have been characterized has something like that been seen."

The researchers showed this not only by tracking gene expression but also by knocking out genes in C. lusitaniae that in brewer's yeast are associated with just meiosis (such as IME2) or just mating (such as STE12). Knocking out either gene scuttled both processes in C. lusitaniae. Restoring the knocked out genes restored the processes.

Reproduction rewired

It appeared as if sometime during its own evolution, C. lusitaniae had completely rewired its reproductive program compared to its "cousin" brewer's yeast. If that were without precedent, perhaps it could just be written off as an oddity, but there is another haploid yeast that has also evolved such a fused program: Schizosaccharomyces pombe. But S. pombe and C. lusitaniae are very distant relatives. Their evolution diverged at least 330 million years ago.

That two such distantly related haploid yeasts should each have evolved a fused program of mating and meiosis makes it seem more likely that there is some generally good reason for doing so, Bennett said. His hypothesis is that coupling of mating and meiosis offers the yeasts an advantage in maintaining their haploid lifestyle by efficiently splitting up the diploid products of mating.

In general, fungi have proven ready to adapt their sexual habits based on their environment, Bennett said. Furthermore, across biology there is an emerging picture that genes involved in sexual reproduction are evolving faster than non-sex genes. But the question of why fungi should prefer a life of haploidy, diploidy, or polyploidy rages as hotly as ever among biologists.



INFORMATION:



In addition to Bennett, Sherwood, and Scaduto, the paper's other author is Sandra Torres (now at University of California–San Francisco).

The National Science Foundation (grant MCB1021120), the National Institutes of Health (grants AI081704, T32GM007601 and F31AI075607), and the Burroughs Wellcome Fund supported the research.



ELSE PRESS RELEASES FROM THIS DATE:

Supervolcano eruptions are triggered by melt buoyancy

2014-01-06
Supervolcano eruptions are triggered by melt buoyancy Jointly issued by ETH Zurich, ESRF and CNRS Supervolcanos are not usual volcanos. By effectively "exploding" as opposed to erupting, they leave a giant hole in the Earth's crust instead of a volcanic cone – a caldera, ...

Pulsar in stellar triple system makes unique gravitational laboratory

2014-01-06
Pulsar in stellar triple system makes unique gravitational laboratory Neutron star, 2 white dwarfs give best opportunity yet to study complex gravitational interactions and may give clue to true nature of gravity Astronomers using the National Science Foundation's ...

Ground-breaking work sheds new light on volcanic activity

2014-01-06
Ground-breaking work sheds new light on volcanic activity Factors determining the frequency and magnitude of volcanic phenomena have been uncovered by an international team of researchers. Experts from the Universities of Geneva, Bristol and Savoie ...

Population stability 'hope' in species' response to climate change

2014-01-06
Population stability 'hope' in species' response to climate change Stable population trends are a prerequisite for species' range expansion, according to new research led by scientists at the University of York. The climate in Britain has warmed over the last ...

After a 49-million-year hiatus, a cockroach reappears in North America

2014-01-06
After a 49-million-year hiatus, a cockroach reappears in North America The cockroach in the genus Ectobius is a major textbook example of an invasive organism, and it is the most common cockroach inhabiting a large region from northernmost Europe to ...

Mine landslide triggered quakes

2014-01-06
Mine landslide triggered quakes Record-breaking slide would bury Central Park 66 feet deep SALT LAKE CITY, Jan. 6, 2014 – Last year's gigantic landslide at a Utah copper mine probably was the biggest nonvolcanic slide in North America's modern history, and included two ...

Self-driving vehicles offer potential benefits, policy challenges for lawmakers

2014-01-06
Self-driving vehicles offer potential benefits, policy challenges for lawmakers Self-driving vehicles offer the promise of significant benefits to society, but raise several policy challenges, including the need to update insurance liability regulations and privacy concerns ...

Study: Half of black males, 40 percent of white males arrested by age 23

2014-01-06
Study: Half of black males, 40 percent of white males arrested by age 23 First contemporary findings on how the risk of arrest varies across race and gender Nearly half of black males and almost 40 percent of white males in the U.S. are arrested by age 23, ...

New study may aid rearing of stink bugs for biological control

2014-01-05
New study may aid rearing of stink bugs for biological control Many people think of stink bugs as pests, especially as the brown marmorated stink bugs spreads throughout the U.S. However, certain stink bugs are beneficial, such as Podisus nigrispinus ...

7 new species of nearctic wasps described and illustrated

2014-01-04
7 new species of nearctic wasps described and illustrated After studying specimens from the Nearctic deposited in the United States National Museum of Natural History and some specimens in the Canadian National Collection of Insects, researchers have found ...

LAST 30 PRESS RELEASES:

Corpse flowers are threatened by spotty recordkeeping

Riding the AI wave toward rapid, precise ocean simulations

Are lifetimes of big appliances really shrinking?

Pink skies

Monkeys are world’s best yodellers - new research

Key differences between visual- and memory-led Alzheimer’s discovered

% weight loss targets in obesity management – is this the wrong objective?

An app can change how you see yourself at work

NYC speed cameras take six months to change driver behavior, effects vary by neighborhood, new study reveals

New research shows that propaganda is on the rise in China

Even the richest Americans face shorter lifespans than their European counterparts, study finds

Novel genes linked to rare childhood diarrhea

New computer model reveals how Bronze Age Scandinavians could have crossed the sea

Novel point-of-care technology delivers accurate HIV results in minutes

Researchers reveal key brain differences to explain why Ritalin helps improve focus in some more than others

Study finds nearly five-fold increase in hospitalizations for common cause of stroke

Study reveals how alcohol abuse damages cognition

Medicinal cannabis is linked to long-term benefits in health-related quality of life

Microplastics detected in cat placentas and fetuses during early pregnancy

Ancient amphibians as big as alligators died in mass mortality event in Triassic Wyoming

Scientists uncover the first clear evidence of air sacs in the fossilized bones of alvarezsaurian dinosaurs: the "hollow bones" which help modern day birds to fly

Alcohol makes male flies sexy

TB patients globally often incur "catastrophic costs" of up to $11,329 USD, despite many countries offering free treatment, with predominant drivers of cost being hospitalization and loss of income

Study links teen girls’ screen time to sleep disruptions and depression

Scientists unveil starfish-inspired wearable tech for heart monitoring

Footprints reveal prehistoric Scottish lagoons were stomping grounds for giant Jurassic dinosaurs

AI effectively predicts dementia risk in American Indian/Alaska Native elders

First guideline on newborn screening for cystic fibrosis calls for changes in practice to improve outcomes

Existing international law can help secure peace and security in outer space, study shows

Pinning down the process of West Nile virus transmission

[Press-News.org] Yeast's lifestyle couples mating with meiosis