Losing genes can be a win in evolutionary terms

Gene loss drives adaptation
Visualisation of a population evolving in a dynamic fitness landscape. Credit: Randy Olson and Bjørn Østman

Loss of gene function is a common occurrence in evolution that is usually associated with loss of fitness. However, it seems that as many say: “where there’s a problem, there is an opportunity“, for as researchers from Leuven University led by Rob Jelier have recently reported 1, gene loss was found to drive adaptation.

To answer the question of how does losing gene function increase the capacity of an organism to adapt and evolve, Jana Helsen and colleagues used about 200 yeast lineages and evolved, sequenced, and phenotyped them. Although as expected, initially the cell’s fitness under a stressful condition was reduced, in not too long a time, compensating mutations helped recover fitness by rescuing the loss of function.

In some cases, those mutants lacking a certain gene became as adapted to the stressful condition as their wild type cousins, who had their whole genome intact. What’s more, all cells who lost genes in different signalling networks followed a predictable mutational route which was also characteristic.

But the finding that I find the most interesting is that losing hub genes, that is, those genes that are hyperconnected with others, leads to an increased capacity to evolve and consequently more and more diverse phenotypes after adaptation. What this result means is that actually losing certain key parts of a genetic network allow for improved adaptation by opening alternative evolutionary paths.

So if gene loss drives adaptation, how would such a circumstance be experienced at another level, say, at our human/social level. What if we would try to translate this to our present –global– circumstance, could we say that lack of a key component to our lives, like freedom of movement, would lead to an improved adaptation to stressful circumstances which could have an evolutionary impact? An interesting question for another day, I think.

References

  1. Jana Helsen, Karin Voordeckers, Laura Vanderwaeren, Toon Santermans, Maria Tsontaki, Kevin J Verstrepen, Rob Jelier (2020) Gene Loss Predictably Drives Evolutionary Adaptation Molecular Biology and Evolution doi: 10.1093/molbev/msaa172

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