Ancient balancing selection maintains incompatible versions of the galactose pathway in yeast

Abstract

Yeast switches for glucose and galactose Some organisms can switch metabolic pathways depending on their environment. One such example is yeast, which can transition between the sugars glucose and galactose as carbon sources. Boocock et al. show that this ability has undergone selection, resulting in the maintenance of two incompatible metabolic pathways in a select set of yeast strains within a single species. A phylogenetic analysis supports that these different pathways are mediated by three genes that differ between strains within and among yeast species and likely have been maintained over 10 million to 20 million years. Science , this issue p. 415

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