Can living organisms influence changes in their genes?

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A wheat leaf infested with the fungus Zymoseptoria tritici shows typical signs of so-called leaf spot, which can lead to severe crop losses. Credit: Dr Janine Haueisen

The evolution of genetic information over time is a key factor in the evolutionary adaptations with which living beings can adapt to changes in their environment. On the one hand, genetic variability occurs during reproduction, where genetic information is split and recombined in developing offspring. In addition, mutations are another important source of genetic variability. This genetic variability then provides the starting point for the action of natural selection, which results in the preferential inheritance of certain advantageous genetic variants and thus allows adaptation to changing environmental conditions.

Mutations occur with varying frequency and at different places throughout an organism’s genome. In multicellular organisms, DNA is packaged by certain proteins, including histones. Changes in these proteins affect the way genetic material is compacted. Researchers suspect that this in turn influences the mutation rate: Many life science research projects address links between such changes and the frequency of mutations. In cancer research, for example, it has been possible to show that such changes and mutations involved in tumor development often occur together.

Taking the example of the fungus Zymoseptoria tritici, a pest of wheat, researchers at the Kiel Evolution Center (KEC) at the University of Kiel have succeeded for the first time in demonstrating a causal relationship between such protein changes and the level of mutation. To this end, scientists from the Kiel University Botanical Institute’s Environmental Genomics Working Group led by Professor Eva Stukenbrock conducted extensive evolutionary experiments. There, the researchers analyzed the rates of mutation in fungal colonies in which they artificially deactivated certain enzymes responsible for natural changes. Compared to unmodified fungi, they were able to determine that the mutation rates differed and that the protein modifications were therefore the direct cause of an altered mutation rate. Kiel scientists today published their new research results in the famous journal Nature Communication.

In-depth evolutionary experiences

In multicellular organisms, DNA is organized using histone proteins. This arrangement of genetic information, which can be viewed as a whole, influences, among other things, the way genetic information is read and replicated. Errors in this process, also known as replication, can lead to mutations, in addition to environmental factors. To study the effect of modifications of the proteins involved in this packaging on the frequency of mutations, the Kiel research team carried out particularly extensive evolutionary experiments. They compared fungal colonies in which certain DNA packaging enzymes were artificially deactivated with unmodified colonies. They then observed the original and modified samples over the course of a year to compare the emergence of genetic variants in the two groups.

In order to rule out the influence of selection processes, the researchers selected a fungal colony at random once a week and developed a new colony with only one cell at a time. In this way, they created a so-called evolutionary bottleneck that corrected the resulting genetic variations in the next generation. In this way, they were able to ensure that the frequency of genetic changes in the fungi was not influenced by selection. Due to the long period of investigation and the high number of parallel approaches, a large repertoire of mutations has thus accumulated in the fungal colonies. Using high-throughput genome sequencing, the researchers then analyzed all of the genetic information from the many different variants and were thus able to determine how often the genetic changes occurred overall.

“Experimental inhibition of epigenetic changes led to a significant change in mutation rates – that is, depending on the type of change, mutations occurred significantly more or less frequently. The changes are therefore directly responsible for the frequency and location of spontaneous mutations in the genome and can influence the evolutionary development of a species, ”says Dr. Michael Habig, scientist in the Environmental Genomics Working Group and first author of the article. our study uses experimental data that was not available for any other species until now to show that different epigenetic modifications and changes in mutation rate are not only correlated, i.e. occur in parallel, but are causally based on each other. “

Can organisms control mutation rates?

The new findings from the Kiel research team at KEC thus provide the first approaches to answer a new research question: whether and how organisms can independently manipulate or optimize their mutation rates. Especially in the relationships between pests and host organisms, such as Zymoseptoria tritici and wheat, it would be plausible that such controlled modifications would take place to accelerate mutual adaptation. “As they evolve together and must respond to mutual changes, there are areas in the genetic information of the host and the pest that must adapt faster than others,” explains Habig. “This could possibly be a point at which an organism acts on its mutation rates to achieve accelerated adaptation to its counterpart.” This would be supported, among other things, by the fact that certain modifications are localized in particular in the areas of the genetic material which help the fungus to overcome the immune system of the plant.

In future research, scientists want to determine whether these interventions in the genome really take place in a targeted manner and are linked to evolutionary adaptation processes. “Our new results are therefore in principle also relevant in various fields of application. The evidence that epigenetic changes and mutation rates are causally related opens up new perspectives for a range of research areas, ”said Stukenbrock, head of the Environmental Genomics working group. and member of KEC. “Among other things, the new findings will help us in the future to better understand the adaptations of plant pests to their hosts or the evolution of tumors,” said Stukenbrock.


Researchers propose an expanded evolutionary concept


More information:
Michael Habig et al, Epigenetic modifications affect the rate of spontaneous mutations in a pathogenic fungus, Nature Communication (2021). DOI: 10.1038 / s41467-021-26108-y

Provided by the University of Kiel

Quote: Can living organisms influence changes in their genes? (2021, October 7) retrieved October 9, 2021 from https://phys.org/news/2021-10-genes.html

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