Mating-type switching paper out

We just published a new paper on the evolution of mating type switching in fission yeast:

Nieuwenhuis, Bart P. S., Sergio Tusso, Pernilla Bjerling, Josefine Stångberg, Jochen B. W. Wolf, and Simone Immler. “Repeated Evolution of Self-Compatibility for Reproductive Assurance.” Nature Communications 9, no. 1 (April 24, 2018): 1639.

In the paper we show experimentally that mating-type switching is highly beneficial under sexual reproduction in fission yeast. If cells cannot change mating type – due to the spatial structuring – cells that are not directly next to another cell will not be able to find a mate of the opposite mating type. Cells that can switch their mating type during asexual reproduction will during growth assure that there is always a mate present as a direct neighbor. These cells can thus mate within their clonal patch, where non-switchers can only mate at the edge of a patch.

Mix of switching and non-switching (of two mating types) fission yeast cells. Black indicate that cells have mated and produced spores, while gray are unmated cells. The black lines are the borders where two non-switchers meet. The black patches are formed by switchers.

Next to showing that there is a strong fitness advantage, we performed experimental evolution. In this experiment we mixed non-switcher strains, let them go through repeated rounds of sexual reproduction that strongly favored mating. Within 25 generations, we re-evolved mating-type switching in 9 out of 20 replicate populations.

Even though mating seems highly beneficial – which should select for maintenance of switching – in nature we see that switching is repeatedly lost. In competition experiments we showed that this is likely caused by a reduced fitness during asexual reproduction of switchers relative to non-switchers. When sexual reproduction is not required – for example when resources are plenty and long-term survival is not needed – prolonged asexual reproduction can locally select for loss of switching.

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