Eukaryotes, including creatures as complex as humans and as simple as yeast, all have mitochondria, which were acquired billions of years ago. Mitochondria are the power house of the eukaryotic cell, required for the efficient conversion of food into energy. This process requires oxygen and is incredibly efficient. Unlike us, yeast also have a secondary pathway called fermentation that can create energy too, but at lower efficiency. In low-oxygen environments, yeast will convert food into low amounts of energy, and fermentation will yield ethanol. Thus, mitochondrial function is an important part of how yeast make the good things in life, including beer, wine and bread.
A clue to the origins of mitochondria is in their DNA. Mitochondria each have their own tiny genomes, which in humans are passed along from mother to child each generation with little variability. This is why mitochondrial DNA is a useful marker to determine genetic relationships between humans. By contrast, when yeast “mate” (they sometimes do that), the result is yeast offspring with equal mitochondria from both parents.
In yeast, this mix of parental mitochondria doesn’t last long, and after a few generations the yeast offspring will contain mitochondria from only one parent. Dr. Warren Albertin and his group created identical yeast, differing only in their mitochondrial DNA (mtDNA). The yeast were grown in low-oxygen and normal-oxygen environments to test fitness, and the results were surprising. All the yeast that contained mtDNA from parent 1 (Saccharomyces cerevisiae) were better at using oxygen to create energy than yeast that contained mtDNA from parent 2 (Saccharomyces uvarum). Not only that, but when grown together the yeast containing mtDNA from parent 1 out-competed yeast containing mtDNA from parent 2 almost entirely!
Mitochondrial has long been overlooked because it only encodes only a handful of genes. With this new study, Albertin’s group demonstrate that variations in mtDNA can have a big impact on yeast energy production.
Summary written by: Mackenzie Thornbury
To read the full paper, please click the following link:
For more on mitochondria and eukaryotic evolution check out this open access article from Dalhousie Evolutionary Biologist John Archibald.
