[GAR+] switches yeast cells from metabolic specialists to metabolic generalists
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Spontaneous switching frequency correlates with environmental niche
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Mathematical modeling suggests strong selection for their bet-hedging functions
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Similar epigenetic switches occur in other fungi and are induced by bacteria
Summary
[GAR+] is a protein-based element of inheritance that allows yeast (Saccharomyces cerevisiae) to circumvent a hallmark of their biology: extreme metabolic specialization for glucose fermentation. When glucose is present, yeast will not use other carbon sources. [GAR+] allows cells to circumvent this “glucose repression.” [GAR+] is induced in yeast by a factor secreted by bacteria inhabiting their environment. We report that de novo rates of [GAR+] appearance correlate with the yeast’s ecological niche. Evolutionarily distant fungi possess similar epigenetic elements that are also induced by bacteria. As expected for a mechanism whose adaptive value originates from the selective pressures of life in biological communities, the ability of bacteria to induce [GAR+] and the ability of yeast to respond to bacterial signals have been extinguished repeatedly during the extended monoculture of domestication. Thus, [GAR+] is a broadly conserved adaptive strategy that links environmental and social cues to heritable changes in metabolism.