Widespread Prion-Based Control of Growth and Differentiation Strategies in <i>Saccharomyces Cerevisiae</i>

Abstract

Theory and experiment suggest that organisms can pre-adapt to future stressors based on reproducible environmental fluctuations experienced by their ancestors. Yet the mechanisms driving such pre-adaptation remain enigmatic. We report that the [SMAUG+] prion allows yeast to anticipate nutrient repletion after periods of starvation, providing a strong selective advantage. By transforming the landscape of post-transcriptional gene expression, [SMAUG+] regulates the decision between two broad growth and survival strategies: mitotic proliferation or meiotic differentiation into a stress-resistant state. [SMAUG+] is common in laboratory yeast strains, where standard propagation practice produces regular cycles of nutrient scarcity followed by repletion. Distinct [SMAUG+] variants are also widespread in wild yeast isolates from multiple niches, establishing that prion polymorphs can be utilized in natural populations. Our data provide a striking example of how protein-based epigenetic switches can be hidden in plain sight and can establish a transgenerational memory that integrates adaptive prediction into developmental decisions.