title: Thermotolerant yeasts selected by adaptive evolution express heat stress response at 30 °C.
abstract: Exposure to long-term environmental changes across >100s of generations results in adapted phenotypes, but little is known about how metabolic and transcriptional responses are optimized in these processes. Here, we show that thermotolerant yeast strains selected by adaptive laboratory evolution to grow at increased temperature, activated a constitutive heat stress response when grown at the optimal ancestral temperature, and that this is associated with a reduced growth rate. This preventive response was perfected by additional transcriptional changes activated when the cultivation temperature is increased. Remarkably, the sum of global transcriptional changes activated in the thermotolerant strains when transferred from the optimal to the high temperature, corresponded, in magnitude and direction, to the global changes observed in the ancestral strain exposed to the same transition. This demonstrates robustness of the yeast transcriptional program when exposed to heat, and that the thermotolerant strains streamlined their path to rapidly and optimally reach post-stress transcriptional and metabolic levels. Thus, long-term adaptation to heat improved yeasts ability to rapidly adapt to increased temperatures, but this also causes a trade-off in the growth rate at the optimal ancestral temperature.
authors.affiliation: Centro de Investigación en Biotecnología, Universidad Autónoma del Estado de Morelos, MX-62209, Cuernavaca, Morelos, México.|Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Luis
authors.initials: L
authors.lastname: Caspeta
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.|Department of Biology and Biological Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.|Department of Biology and Biological Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.|Novo Nordisk Foundation Center for Biosustainability, DK-2970 Hørsholm, Denmark.|Science for Life Laboratory, KTH Royal Institute of Technology, SE17165 Solna, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Nielsen