Yeast cells appear to exhibit mate choice, selecting partners that may increase the chances of their offspring’s success, according to a new study published in Cell Reports. The research sheds light on the evolution of sexual reproduction and suggests that mate preferences may be an ancient and fundamental mechanism.
Yeast Exhibit Mating Preferences
The findings emerged from an experiment conducted in the lab of Prof. Yitzhak Pilpel at the Weizmann Institute of Science, involving approximately 10 million yeast cells from roughly 100 different strains. Researchers tracked the mating choices of the single-celled organisms as they mingled freely.
Baker’s yeast reproduces through self-replication when conditions are favorable, but forms spores during starvation. These spores, carrying half of the parent cell’s genetic material, come in two mating types, a and α, which fuse to create offspring.
While mating between different yeast strains is rare in nature, it offers insights into how traits are inherited and whether organisms display partner preferences. The study, led by Dr. Sivan Kaminski Strauss under the supervision of Pilpel and Dr. Orna Dahan, involved placing spores from 100 strains in a test tube for 20 hours.
Researchers inserted identifying barcodes into the genetic code of each strain and a mechanism that linked the barcodes of both parents in the offspring. This allowed them to determine parentage and mating frequency.
The team discovered that some yeast strains systematically avoided mating with others. Comparisons between successful and unsuccessful pairings revealed differences beyond simple sexual activity, suggesting specific mating preferences.
The experiment was conducted with two food sources: one preferred by most strains and another more difficult to digest. When the preferred food was available, yeast chose partners that produced fitter offspring.
“This discovery brings us closer to answering a fundamental question in evolution: Is the ability to choose a mate an integral part of sexual reproduction, or is it a refinement that evolved later?” said Pilpel. “The fact that such preferences exist in yeast suggests that this is an ancient and fundamental mechanism.”
Researchers are now investigating whether silencing the genes responsible for mating preferences eliminates sexual reproduction altogether, and how yeast strains identify suitable partners, potentially through unique chemical features in their pheromones.
The Recipe for Successful Offspring
The study also examined how “success in life,” or fitness, is passed from parents to offspring. Yeast’s short generation time—less than two hours—allowed for quick measurement of fitness through growth competitions.
When the preferred food was available, fitter parents tended to have fitter offspring. However, when the preferred food was absent, the genetic difference between parents mattered most; offspring fitness increased with parental genetic distance, up to a certain point.
Researchers developed a statistical model to predict offspring fitness based on parental traits and environmental conditions.
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