Genetic tradeoff: Harmful genes are widespread in yeast but hold hidden benefits

Oct 25, 2012

The genes responsible for inherited diseases are clearly bad for us, so why hasn't evolution, over time, weeded them out and eliminated them from the human genome altogether? Part of the reason seems to be that genes that can harm us at one stage of our lives are necessary and beneficial to us at other points in our development.

The idea that the same gene can be both beneficial and harmful, depending on the situation, is called antagonistic pleiotropy. The theory has been around since the 1950s and has been used to explain aging, cancer and .

But until now, no one has been able to determine just how common antagonistic pleiotropy is—on a genome-wide scale—in any organism. In a paper to be published online Oct. 25 in the journal Cell Reports, Jianzhi "George" Zhang of the University of Michigan and his coworkers report that antagonistic pleiotropy is very common in yeast, a single-celled organism used by scientists to provide insights about genetics and .

Zhang and his colleagues say the findings have broad biomedical and evolutionary implications.

"In any given environment, yeast expresses hundreds of genes that harm rather than benefit the organism, demonstrating widespread antagonistic pleiotropy. The surprising finding is the sheer number of such genes in the that have such properties," said Zhang, a professor in the Department of Ecology and .

"From our yeast data we can predict that humans should have even more antagonistic pleiotropy than yeast," he said. "This suggests that special cautions are needed when treating inherited diseases, because a treatment that removes a disease-causing may lead to in other aspects of life."

Yeast has about 6,000 genes, about 1,000 of which are essential – eliminate any of them and the organism dies. Zhang and his colleagues worked with a set of 5,000 laboratory strains of yeast in which one non-essential gene had been deleted from each strain. Each strain was tagged with a genetic "barcode" to allow researchers to identify it later.

Zhang and his grew all 5,000 strains together in a single test tube and compared the growth rates of each strain, under various environmental conditions, to the growth rates of "wild type" yeast strains without gene deletions.

This side-by-side comparison allowed them to determine which genes were beneficial (increased growth rate) and which ones were harmful (decreased growth rate) under the six environmental conditions. Different mixes of nutrients and chemical stressors, such as ethanol, were added to the yeasts' growth media to create the six environmental conditions.

The researchers found that for each of the six conditions, on average, the yeasts expressed about 300 genes that slowed their growth and were therefore classified as harmful. Deleting those genes resulted in more rapid growth.

But many of the that were harmful under one set of environmental conditions proved to be beneficial under another, demonstrating widespread antagonistic pleiotropy, Zhang said.

"There are a lot of theories – some of them relating to aging, cancer and genetic disease – that invoke antagonistic pleiotropy. But it's not easy to measure, and empirically we have not known much about it," Zhang said. "Now, in yeast, we have found that antagonistic pleiotropy is very common."

Explore further: Parasitic worm genomes: largest-ever dataset released

Related Stories

Complexity not so costly after all, analysis shows

Sep 27, 2010

The more complex a plant or animal, the more difficulty it should have adapting to changes in the environment. That's been a maxim of evolutionary theory since biologist Ronald Fisher put forth the idea in 1930.

Making tomorrow's bioenergy yeasts strong

Aug 25, 2011

Cornstalks, wheat straw, and other rough, fibrous, harvest-time leftovers may soon be less expensive to convert into cellulosic ethanol, thanks to U.S. Department of Agriculture (USDA) scientists' studies of a promising new ...

Recommended for you

Parasitic worm genomes: largest-ever dataset released

12 hours ago

The largest collection of helminth genomic data ever assembled has been published in the new, open-access WormBase-ParaSite. Developed jointly by EMBL-EBI and the Wellcome Trust Sanger Institute, this new ...

Bitter food but good medicine from cucumber genetics

Nov 27, 2014

High-tech genomics and traditional Chinese medicine come together as researchers identify the genes responsible for the intense bitter taste of wild cucumbers. Taming this bitterness made cucumber, pumpkin ...

New button mushroom varieties need better protection

Nov 27, 2014

A working group has recently been formed to work on a better protection of button mushroom varieties. It's activities are firstly directed to generate consensus among the spawn/breeding companies to consider ...

Cataloguing 10 million human gut microbial genes

Nov 25, 2014

Over the past several years, research on bacteria in the digestive tract (gut microbiome) has confirmed the major role they play in our health. An international consortium, in which INRA participates, has developed the most ...

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.