The role of mitotic recombination in genome evolution of polar phytoplankton

尽管极地海洋的环境条件恶劣，但这些生态系统拥有重要的生物多样性。这种生物多样性是如何演变的，它是生物技术、农业和医药所用新产品的生产性生态系统和资源的基础，在很大程度上仍不清楚。这种知识差距的一个原因是，我们对突变和重组作为主要进化力量如何塑造极地生物以及它们的基因如何使它们在严酷的极地生长条件下茁壮成长知之甚少。可以说，大多数驱动生物多样性的遗传变异源于突变。因为它们的速率随温度而增加。极端的突变率表明，极地生物可能需要科普更高的突变负荷。极地硅藻基因组提供的证据表明，这些微藻受益于突变率的提高，产生遗传多样性，以应对快速变化的环境条件（如冷冻和融化），而不进行有性重组。然而，直接的实验证据缺失。该项目将调查DNA损伤是否在极性硅藻与非极性对应物中增强，以及有丝分裂重组如何有助于适应性遗传变异。使用基于荧光的测定结合基因组重测序来量化极性和非极性硅藻物种在冷和热应激后的DNA损伤。DNA修复诱导的有丝分裂重组如何导致两种硅藻物种之间的遗传变异和差异将使用两种核心DNA修复酶（BRCA 2，KU 70）进行测试，并揭示温度胁迫下对DNA损伤和适应性（生长速率）的后续影响。因此，该项目的数据将为极端极地环境如何塑造极地浮游植物中基因和基因组的进化奠定基础，这些基因和基因组是生物技术中使用的新型酶的生产性食物网和资源的基础。

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.