The role of mitotic recombination in genome evolution of polar phytoplankton

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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) andrevealing 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.