The role of mitotic recombination in genome evolution of polar phytoplankton

Despite the harsh environmental conditions in polar oceans, these ecosystems harbour
significant biodiversity. How this biodiversity underpinning productive ecosystems and
resources for novel products used in biotechnology, agriculture and medicine has evolved
largely remains unknown. One reason for this knowledge gap is that we only know little as to
how mutation and recombination as major evolutionary forces shape polar organisms and
therefore their genes enabling them to thrive under the harsh polar growth conditions.
Arguably, most of the genetic variation driving biological diversity stems from mutations. As
their rate is temperature dependent with increasing. Mutation rates at the extreme ends, it
suggests that polar organisms likely need to cope with higher mutational loads. Polar diatom
genomes have provided evidence that these microalgae benefit from elevated mutation rates,
generating genetic diversity to respond to fast-changing environmental conditions (e.g.
freezing and melting) in the absence of sexual recombination. However, direct experimental
evidence is missing.
The project will investigate if DNA damage is enhanced in a polar diatom vs a non-polar
counterpart and how mitotic recombination contributes to the genetic variation that is adaptive.
Using fluorescence-based assays in combination with genome re-sequencing to quantify DNA
damage after cold and heat stress in a polar and a nonpolar diatom species. How DNA-repair
induced mitotic recombination contributes to genetic variation and differences between both
diatom species will be tested using two core DNA-repair enzymes (BRCA2, KU70) and
revealing subsequent effects on DNA damage and fitness (Growth rates) under temperature
stress. Thus, data from this project will lay the foundation for how the extreme polar
environment shapes the evolution of genes and genomes in polar phytoplankton underpinning
productive food webs and resources for novel enzymes used in biotechnology.