Poster Presentation Society for Molecular Biology and Evolution Conference 2016

Fitness pleiotropy and the phenotypic basis of adaptation in experimentally evolving yeast (#413)

Yuping Li 1 , Sandeep Venkataram 1 , Atish Agarwala 1 , Dmitri Petrov 1 , Gavin Sherlock , Daniel Fisher 1
  1. Stanford University, Stanford, CALIFORNIA, United States

Understanding how the fitness of a beneficial mutation selected in one environment varies in other environments is essential for understanding the evolutionary process. However, difficulty in obtaining a large number of independent adaptive mutations, and being able to measure their fitness across multiple environments has constrained our ability to study the pleiotropy of beneficial mutations. We have overcome these limitations using a DNA barcode approach, which we have used to isolate 4800 yeast lineages independently evolved in glucose-limited batch culture conditions. High throughput fitness measurements have shown that thousands of these lineages are adaptive, and whole-genome sequencing has identified the genetic basis of adaptation in 300 lineages. To investigate fitness pleiotropy, we have systematically manipulated the exponential or stationary growth phases within each growth cycle, and remeasured fitness. Our experiments showed that the fitnesses of the adapted clones are highly pleiotropic across these conditions, and in some cases exhibit antagonistic pleiotropy. In addition, the measured fitness is dependent on both the identity of the specific genes carrying a mutation and on the mutation types (e.g. missense vs frameshift). We have also conducted detailed physiological experiments to study the phenotypic basis of the observed fitness pleiotropy. Measurement of the growth cycle and metabolism of the adapted strains indicates that the adaptive mutations affect multiple phenotypic traits and helps explain the strong fitness pleiotropy observed. Taken together, our results suggest that fitness is exquisitely sensitive to specific environmental conditions and that adaptive mutations exhibit high phenotypic pleiotropy to drive these fitness effects.