Abstracts (first author)

Poster 

Genetic architecture promotes the evolution and maintenance of cooperation: the evolutionary constraint of coding overlaps on functionally unrelated genes

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Author(s): Frénoy A, Taddei F, Misevic D

Summary:

When cooperation has a direct cost and an indirect benefit, a selfish behavior is more likely to be selected for than an altruistic one. Kin and group selection do provide evolutionary explanations for the existence of stable populations of cooperators in nature, but we still lack the full understanding of the genomic mechanisms that can prevent cheater invasion. We used Aevol, an agent-based, in silico genomic platform to evolve populations of digital organisms that compete, reproduce, and cooperate by secreting a costly public good. We found that populations of phenotypically equal cooperating individuals often have very different abilities to resist cheater invasion. To understand the underlying mechanisms, we performed bio-inspired genomics analysis by determining and comparing the locations of metabolic and secretion genes, as well as the relevant promoters and terminators. We found that populations of cooperators characterized by the strong association between metabolic and secretion genes (promoter sharing, overlap via frame shift or sense-antisense encoding) were more robust to cheater invasion than ones where such association was weak. We performed mutation analysis of the evolved individuals and determined that the accessibility of mutations decreasing cooperation without decreasing overall fitness was negatively correlated with the amount of operons and overlap between secretion and metabolism. Effectively, cooperation evolved to be protected and robust to mutations through overlapping genetic architecture, especially when cooperation was costly. Due to operon sharing and gene overlap, even when mutations that eliminate cooperation appear, they are likely to be selected against due to their simultaneous and direct negative effect on fitness. Our results uncover an important genetic mechanism for the evolution and maintenance of cooperation, and suggest promising methods for preventing loss of genes introduced into biological synthetic organisms.



Abstracts (coauthor)

Summary:

The evolution of cooperation and the evolution of sex remain two of the most widely debated evolutionary topics, affecting communities of species ranging from microorganisms to humans. Both present a similar dilemma of evolving and maintaining a trait with long-term benefit and short-term cost, and there is no unifying theory for either. It has been suggested that plasmid conjugation, a form of bacterial sex, promotes cooperation based on secretion of public good molecules. Here we propose that the relationship between conjugation and secretion goes in both directions: plasmid transfer may promote cooperation by spreading the cooperating plasmid, but also, if cooperation is selected for, it may in turn promote sex, as an effective mechanism for its maintenance. In short, sex affects cooperation, but cooperation may also affect sex. To test these theories, we used an in silico system, Aevol, in which large populations of digital organisms compete, mutate and evolve over tens of thousands of generations. Digital individuals may evolve their plasmid donor and recipient abilities as well as the level of secretion of the costly, diffusible public good molecule. Results of our experiments show that transfer was more likely to evolve when secretion was present than when individuals could not secrete. It was primarily the donor ability that increased, while only in a handful of cases the recipient ability decreased, making individuals more immune to plasmid infection. However, the secretion genes were not always located on the plasmid, as we expected. Instead, especially when the transfer rate evolved to high values, it was the metabolic genes that were primarily encoded on the plasmid, turning it into a kind of a selfish genetic element. In conclusion, we demonstrate that in the diverse communities of digital organisms, individuals engage in complex relationships relying on costs and benefits of both cooperation and sex that in turn shape their evolutionary fate.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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