About this Event
Systems Biology Lecture Series:
The Systems Biology Lecture Series is dedicated to highlighting the many facets of Systems Biology and its impact on biomedicine. It will encompass four lectures per year and will feature key opinion leaders in this field. We are delighted to welcome Dr. Timothy Mitchison as the inaugural speaker for the series
Title: Evolvability, robustness, and natural selection
Abstract: Evolvability is the ability of organisms to bring forth adaptive and novel traits. Whether evolvability itself can be subject to Darwinian evolution is a fundamental question in evolutionary biology. To answer this question, we need to find out how natural selection may affect evolvability. It has been proposed that during evolution on a rugged adaptive landscape, strong selection may hinder the traversal of fitness valleys that is essential to reach high adaptive peaks. However, little experimental evidence supports this and other proposals for the role of selection in evolvability. To provide such evidence, we performed experimental evolution on light-emitting yellow fluorescent proteins. We first subjected these proteins to several generations of mutation and selection (strong or weak) for their native yellow color. We then continued evolution, but selected for the new color of green fluorescence. We found that strong selection for the old, yellow color enhanced evolvability of the new green color. To find out why, we subjected the evolving populations to high-throughput DNA sequencing, studied the evolutionary dynamics of abundant genetic variants, and examined their properties through biochemical assays. We found that strong selection enhances evolvability by increasing both mutational robustness and protein foldability. Our experiments not only demonstrate a positive role for natural selection in enhancing evolvability. They also prove that natural selection can enhance the robustness of biological systems to mutations. In doing so, selection can help a population circumnavigate rather than traverse fitness valleys. In sum, Darwinian evolution may help create the conditions necessary for its own success.
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