Yeast cells decide whether to have sex with each other within 2 minutes of meeting

Yeast cells can decide to mate within two minutes of meeting each other, a new research has found.

According to one of the authors of the study, from Imperial College London, the findings of the study could be helpful for researchers looking at how cancer cells and stem cells develop.

Yeasts are single-celled microbes that scientists often use as model organisms, to understand how cells work.

Yeasts usually reproduce asexually, by a process called budding, where a part of the cell is pinched off and becomes a new cell, identical to the original.

However, there are times when yeast cells reproduce sexually, by mating.

The mating process involves one cell of each sex joining together, then mixing their DNA and splitting apart again.

To do this, the cells each have to produce a nodule that they can join together, called a shmoo. The process of shmooing takes around two hours.

For the new study, researchers from Imperial College London, Université de Montréal, McGill University and the University of Edinburgh determined that a yeast cell's decision to mate is controlled by a chemical change on a single protein.

This change takes place two minutes after the cell detects a pheromone produced by the opposite sex.

The study team also found that in order for the mating process to be switched on, the pheromone must reach a critical concentration in the environment around the yeast cell.

Below this concentration, the yeast cell continues to reproduce asexually.

Dr Vahid Shahrezaei, one of the authors of the study from the Department of Mathematics at Imperial College London, said: "Shmooing is a very energy-intensive process for yeast cells. We think this switching process at a certain pheromone concentration may have evolved to make sure the cells only get prepared for sexual reproduction if a mate is sufficiently close enough and able to mate."

The researchers used a highly complex mathematical model to find what switches the mating process on and off, factoring in experimental data about the concentration of pheromones around the cell, the concentrations of different proteins relevant to mating inside the cell and how strongly these proteins bind together.

Dr Shahrezaei said: "Yeast cells live in a very noisy environment - they are surrounded by different chemicals, including pheromones and food, and their own machinery inside the cell produces lots of biomolecules that interact with each other. We wanted to see how cells make sense of this noisy environment and work out what is happening, at a molecular level, to make a important decision like mating.

"By combining experiments and mathematical modelling that take lots of different factors into consideration, we have been able to show exactly what is happening inside a yeast cell to make it decide whether to mate with another cell. We also showed that the mechanism that leads the cells to make their decision is very robust, meaning it is not affected by molecular noise in the environment."

Senior author Dr Stephen Michnick, a Université de Montréal biochemistry professor and Canada Research Chair in Integrative Genomics, said: "Although yeast is dramatically different from people, at a molecular and cellular level we have a lot in common.

"The same molecules that create the switching decision in yeast are found in very similar forms in human cells. Similar switching decisions to those made by yeast are made by stem cells during embryonic development and become dysfunctional in cancers."

The study has appeared in the journal Nature.