Experimental Evolution of Yeast for High-Temperature Tolerance.

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Thermotolerance is crucial for cell survival at high temperatures.
• The genetic basis for achieving prolonged thermotolerance through mutation accumulation is not fully understood.
• Previous studies identified some high-temperature growth (Htg+) genes, but the evolutionary process remains unclear.

Purpose of the Study:

• To investigate the genetic mutations enabling Saccharomyces cerevisiae to adapt and grow at elevated temperatures (42°C).
• To identify genes and pathways involved in thermotolerance acquisition through experimental evolution.
• To understand how cells accumulate mutations for enhanced high-temperature survival.

Main Methods:

• Experimental evolution of yeast with stepwise temperature increases.
• Whole genome resequencing of evolved strains and the parental strain.
• Functional categorization of mutations and pooled segregant analysis.
• Experimental validation of candidate thermotolerance mutations.

Main Results:

• 153 mutations (SNVs, INDELs, copy number variations) were identified in evolved strains.
• Enriched mutations were found in the SWI/SNF complex and F-type ATPase, suggesting their role in thermotolerance.
• Mutations in stress-associated pathways (Hog1, RAS-cAMP, Rho1-Pkc1) were prevalent, indicating modification of existing stress responses.
• Causative mutations for high-temperature growth were identified and validated.

Conclusions:

• Yeast can achieve high-temperature growth (Htg+) by accumulating diverse genetic mutations.
• The SWI/SNF complex, F-type ATPase, and general stress signaling pathways are critical for thermotolerance.
• Experimental evolution combined with genomics provides insights into the genetic basis of thermal adaptation.