Scientists at Vanderbilt University are raising a glass to the discovery of a previously ignored source of genetic diversity in wine yeast strains. The finding could explain some of the variation in wine vintages available to consumers and open the door to refining wine flavors and crafting all new vintages.

Many strains of the brewer’s yeast species, Saccharomyces cerevisiae, are responsible for the fermentation of wine from grapes. Different strains of the same species usually share most of their DNA except for key single base variations at a few thousand or million places throughout the genome. These variations can lead to differences between strains that might affect fermentation and the resulting wine.

Given the diverse types and flavor profiles in the wine world, you might expect there to be great genetic variation between the yeast strains that make it, but researchers have struggled to find much genetic evidence to explain the differences in wine fermentation by different yeast strains, since wine yeast strains share most of the same A’s, T’s, C’s, and G’s of the genome.

Dr. Antonis Rokas and graduate student Jacob Steenwyk at Vanderbilt University thought that there must be something hiding in the wine yeast genomes that could explain the differences between the strains. They decided to look at something called “copy number variations” between strains. Unlike single base variations in the genome, copy number variations involve large chunks of DNA that are either amplified or deleted in a strain.

Rokas and Steenwyk compared the genome sequences of 132 different wine yeast strains, scanning for copy number variations between the strains. They were not disappointed, as they found thousands of genes that are either present in extra copies or completely missing in different strains.

The researchers were even able to predict the functions of some of these genes. For example, genes coding for copper resistance were frequently turned up or down in the various strains. This makes sense, since vintners have been using copper-containing chemicals for decades to prevent blight. Another gene that is present in extra copies is involved in digesting sugars, likely resulting in a drier wine. Interestingly, the same sugar digesting genes could also be turned down in other strains, possibly leading to a sweeter wine.

It is now possible to ask questions about how amplified or deleted genes could affect the wine made by different yeast strains. All it might take is an intrepid geneticist with a discerning palate to crack the code for the perfect wine, if such an achievement is even possible!



DOI: 10.1534/g3.117.040105