Role of epistatic interactions in evolution

Project Information

EPISTAT

Grant agreement ID: 101088581

DOI

10.3030/101088581

EC signature date 25 February 2023

Start date 1 September 2023

End date 31 August 2028

Funded under

• European Research Council (ERC)

Total cost

€ 1 970 533,00

EU contribution

€ 1 970 533,00

Coordinated by

JYVASKYLAN YLIOPISTO
Finland

Periodic Reporting for period 1 - EPISTAT (Role of epistatic interactions in evolution)

Reporting period: 2023-09-01 to 2026-02-28

Summary of the context and overall objectives of the project

The project EPISTAT investigates the role interactions between mutations in evolution, these genetic interactins are also referred as epistatic interactions. Epistatic interactions are understood to be important in some aspects of evolutionary theory, such as in the formation of new species. However, their role in some other aspects, such as adaptation, has been more controversial as there has been some debate over much much they contribute to variation that is available to selection. Some aspects of this debate are rather technical. These debates can only be solved empirically, so our goal in this project is to investigate the properties of epistatic interactions. What is the probability that two new mutations interact, and what is the distribution of their effects. Understanding these aspects of epistatic interactions is fundamental to evolutionary theory.

To address these questions we are performing two large scale experiments:
WP1: Probability and distribution of epistatic effects
We have previously developed lines of the filamentous fungus Neurospora crassa that different spontaneous mutations. We are making large cross between all of these lines to estimate what is the probability that two mutations interact, and what is the distribution of their effects. The mean of this distribution is an important parameter in determining what is the role of epistatic interactions in adaptation.

WP2: Probability of incompatible interactions and their properties
We using experimental evolution with fission yeast to investigate how often populations that adapt to new environments will end up having mutations that will cause incompatible interactions when they are brought together in an individual. These kinds of incompatible interactions are important in the evolution of reproductive isolation between populations that can eventually lead to formation of new species.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The nature of this project involves large scale experiment that take a long time to perform. These would not be possible without ERC support. However, as a consequence of these large experiments the results of this project are not ready after two years.

WP1: Probability and distribution of epistatic effects
We have completed producing most of the offspring and are genotyping and phenotyping these offspring at the moment. We had to revise our original plan to overcome some technical difficulties, but we have solved these issue now. We anticipate that we will have results from this experiment within the next few years.

WP2: Probability of incompatible interactions and their properties
Our experimental populations have now gone through approximately 750 generations of experimental evolution. Preliminary results indicate that not much changes have happened in the control populations where they experienced a standard laboratory nutrient medium all the time. Although, there may be subtle differences in their growth compared to the ancestor. However, in population that experienced an environment where a particular anvironmental stress increased slowly over time and then decreased again. Our preliminary results indicate that these populations have adapted to the novel conditions. Populations that adapted to slowly increasing potassium chloride concentration are now able to grow at 2M KCl solution, while the ancestors of those populations are not able to grow in this environment.

We did experience some technical challenges while setting up the evolution experiment, which did caused a delay, but we have had no major problems with the evolution experiment since. We are now in the process of sequencing these populations, and next year we will be characterizing whether any of the mutations that happened in these lines exhibit incompatible interactions, and further characterizing the properties of these interactions.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

It is still too early to know the impacts of the results of this project. This is will become apparent in the next three years. However, we still expect that our results will allow adressing long standing questions in evolutionary biology.